Neurology Techniques: TMS and Imaging
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Neurology Techniques: TMS and Imaging

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Questions and Answers

What technology is used to enhance the safety of brain surgery?

  • Electromyography
  • Tractography
  • Diffusion Tensor Imaging
  • Navigated TMS (correct)

    • Tractography involves the use of MRI-based diffusion tensor imaging.

    True

    What does EMG stand for?

    Electromyography

    ________ is a technique that helps visualize white matter pathways in the brain.

    <p>Tractography</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>N.VII = Facial nerve associated with control of muscles of facial expression EMG = Technique used to assess the electrical activity of muscles Navigated TMS = Non-invasive stimulation method used in brain mapping Tractography = Imaging technique for mapping brain's white matter pathways</p> Signup and view all the answers

    Which of the following is NOT a function associated with the basal ganglia?

    <p>Visual perception</p> Signup and view all the answers

    The basal ganglia are located at the base of the forebrain and the top of the midbrain.

    <p>True</p> Signup and view all the answers

    What is the primary role of the direct pathway in the basal ganglia?

    <p>Facilitation of thalamocortical projections</p> Signup and view all the answers

    The basal ganglia modulate _______ reflex arcs, typically through inhibition.

    <p>spinal</p> Signup and view all the answers

    What is the first line of therapy for Parkinson's disease?

    <p>Drugs (L-Dopa, Dopaminagonists)</p> Signup and view all the answers

    Match the following components of the basal ganglia pathways with their roles:

    <p>Striatum = Input region Globus pallidus interna = Major output to thalamus Substantia nigra pars reticularis = Inhibition of thalamocortical projections GPe = Indirect pathway component</p> Signup and view all the answers

    Which of the following tasks do the basal ganglia NOT contribute to?

    <p>Visual processing</p> Signup and view all the answers

    Deep brain stimulation is used in cases of drug resistance for Parkinson's disease.

    <p>True</p> Signup and view all the answers

    Name one neurophysiological biomarker used in DBS for Parkinson's disease.

    <p>Local field potential or neuronal firing.</p> Signup and view all the answers

    The indirect pathway of the basal ganglia facilitates movement.

    <p>False</p> Signup and view all the answers

    What structure within the basal ganglia is responsible for input from the cortex?

    <p>Striatum</p> Signup and view all the answers

    The primary function of the vestibulocerebellum is the maintenance of ______ and equilibrium.

    <p>posture</p> Signup and view all the answers

    Match the following components of the cerebellum with their primary functions:

    <p>Vestibulocerebellum = Maintenance of posture and equilibrium Spinocerebellum = Error correction and adjust posture Cerebrocerebellum = Planning and programming movements</p> Signup and view all the answers

    The basal ganglia are primarily embedded in complex _______ loops.

    <p>motor</p> Signup and view all the answers

    Which nuclei are major outputs from the basal ganglia to the thalamus?

    <p>Globus pallidus interna and Substantia nigra pars reticularis</p> Signup and view all the answers

    Which symptom is NOT typically associated with Parkinson's disease?

    <p>Enhanced reflexes</p> Signup and view all the answers

    Adverse effects of DBS include cognitive dysfunction and hallucinations.

    <p>True</p> Signup and view all the answers

    What is one strategy to avoid adverse effects during DBS treatment?

    <p>Electrophysiologically optimized placement of the DBS electrodes.</p> Signup and view all the answers

    Parkinson's disease can cause ______ instability as a cardinal sign.

    <p>postural</p> Signup and view all the answers

    Which of the following best describes PAC in the context of DBS?

    <p>Phase Amplitude Coupling</p> Signup and view all the answers

    What type of receptors in the striatum yield to inhibition?

    <p>D2 receptors</p> Signup and view all the answers

    Cortical stimulation results in a biphasic response in the basal ganglia output nuclei.

    <p>False</p> Signup and view all the answers

    What disease is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta?

    <p>Parkinson's disease</p> Signup and view all the answers

    The ______ of dopaminergic neurons leads to hyperactivity of SNret in Parkinson's disease.

    <p>loss</p> Signup and view all the answers

    Match the following aspects of motor control with their roles:

    <p>Initiation of movements = Starting motion Termination of movements = Stopping motion Stabilization of movements = Maintaining balance during motion Stabilizing muscles at rest = Preparing for movement</p> Signup and view all the answers

    What happens after an increase in activity from cortical stimulation in the basal ganglia?

    <p>Inhibition of thalamocortical projections</p> Signup and view all the answers

    D1 receptors in the striatum yield to inhibition.

    <p>False</p> Signup and view all the answers

    What is the response observed in the third phase of cortical stimulation in the basal ganglia?

    <p>Increased activity with inhibition of thalamocortical projections</p> Signup and view all the answers

    The substantial loss of ______ neurons in Parkinson's disease affects movement initiation.

    <p>dopaminergic</p> Signup and view all the answers

    What effect does the loss of dopaminergic neurons have on thalamocortical projections?

    <p>Inhibition of impulse transmission</p> Signup and view all the answers

    What is a common cardinal sign of Parkinson's disease?

    <p>Increased muscle tone</p> Signup and view all the answers

    Deep brain stimulation (DBS) can be used to treat all types of movement disorders.

    <p>False</p> Signup and view all the answers

    What is the primary purpose of using extracellular microelectrodes in DBS?

    <p>To record neuronal firing and local field potentials</p> Signup and view all the answers

    One of the primary adverse effects of DBS is __________.

    <p>hallucinations</p> Signup and view all the answers

    Match the following types of DBS optimization with their descriptions:

    <p>aDBS = Closed loop stimulation Directional stimulation = Electrode optimization Neuronal firing analysis = Targeting optimal DBS location Electrophysiologically optimized placement = Reducing adverse effects</p> Signup and view all the answers

    Which of the following symptoms is related to bradykinesia?

    <p>Impaired facial expression</p> Signup and view all the answers

    Phase amplitude coupling (PAC) refers to the synchronization effects in local field potentials.

    <p>True</p> Signup and view all the answers

    Name one neuropsychiatric symptom that can occur in Parkinson's disease.

    <p>Depression</p> Signup and view all the answers

    The __________ is responsible for planning and programming movements in the cerebellum.

    <p>Cerebrocerebellum</p> Signup and view all the answers

    Which of the following therapies is considered first-line treatment for Parkinson's disease?

    <p>L-Dopa</p> Signup and view all the answers

    Which of the following is NOT a function associated with the basal ganglia?

    <p>Vision modulation</p> Signup and view all the answers

    The direct pathway in the basal ganglia primarily inhibits thalamocortical projections.

    <p>False</p> Signup and view all the answers

    What is the primary role of the indirect pathway in the basal ganglia?

    <p>Inhibition of thalamic output</p> Signup and view all the answers

    The basal ganglia are embedded in complex _______ loops.

    <p>motor</p> Signup and view all the answers

    Match the following components of the basal ganglia with their functions:

    <p>Striatum = Input from the cortex Globus pallidus interna = Output to thalamus Substantia nigra pars reticularis = Output to thalamus Subthalamic nucleus = Modulates indirect pathway</p> Signup and view all the answers

    What is the role of the basal ganglia in procedural learning?

    <p>It aids in the development of motor skills.</p> Signup and view all the answers

    The output nuclei of the basal ganglia include the striatum and the subthalamic nucleus.

    <p>False</p> Signup and view all the answers

    Which nuclei are primarily responsible for input from the cortex into the basal ganglia?

    <p>Striatum</p> Signup and view all the answers

    The basal ganglia play a role in regulating ______ movements.

    <p>voluntary</p> Signup and view all the answers

    Which characteristic best describes the basal ganglia's involvement in cognition?

    <p>Supports learning through reinforcement</p> Signup and view all the answers

    What effect do D1 receptors in the striatum have on movement?

    <p>Excitation</p> Signup and view all the answers

    The hyperactivity of SNret in Parkinson's disease contributes to the inhibition of thalamocortical projections required for the initiation of movements.

    <p>True</p> Signup and view all the answers

    Name a type of response observed due to cortical stimulation in the basal ganglia output nuclei.

    <p>Triphasic response</p> Signup and view all the answers

    The _____ of dopaminergic neurons affects movement initiation in Parkinson's disease.

    <p>loss</p> Signup and view all the answers

    Match the following pathways with their functions in the striatum:

    <p>D1 receptors = Excitation D2 receptors = Inhibition Thalamocortical projections = Impulse transmission facilitation Corticostriatal projections = Input to striatum</p> Signup and view all the answers

    What is one of the primary motoric tasks associated with the basal ganglia?

    <p>Initiation of movements</p> Signup and view all the answers

    Cortical stimulation in the basal ganglia results in only a decrease of activity.

    <p>False</p> Signup and view all the answers

    What typically follows the disinhibition of thalamocortical projections during cortical stimulation?

    <p>Increased activity</p> Signup and view all the answers

    In the degenerative process of Parkinson's disease, there is a loss of _______ neurons in the substantia nigra pars compacta.

    <p>dopaminergic</p> Signup and view all the answers

    What is one consequence of decreased dopaminergic activity in the basal ganglia?

    <p>Inhibition of thalamocortical projections</p> Signup and view all the answers

    Which of the following modalities is used for monitoring the hemodynamic status during surgery?

    <p>Metabolic tracking</p> Signup and view all the answers

    Noise in the operating room can consist of both technical and biological noise.

    <p>True</p> Signup and view all the answers

    What does SNR stand for in the context of intraoperative monitoring?

    <p>Signal-to-noise ratio</p> Signup and view all the answers

    Intraoperative monitoring methods assess the functional _______ of neural pathways.

    <p>integrity</p> Signup and view all the answers

    Match the following monitoring modalities with their descriptions:

    <p>Electroneurography = Measures nerve conduction velocity and CMAP EMG = Records spontaneous muscle activity EEG = Monitors brain electrical activity Evoked Potentials = Records brain response to stimuli</p> Signup and view all the answers

    Which of the following is NOT a type of evoked potential?

    <p>EOG</p> Signup and view all the answers

    Spontaneous activity in EMG can provide acoustic feedback during surgery.

    <p>True</p> Signup and view all the answers

    What type of stimulation is associated with Motor evoked potentials?

    <p>Transcranial Magnetic Stimulation (TMS)</p> Signup and view all the answers

    The _______ is a recommended frequency range to be monitored for technical noise.

    <p>50/60 Hz</p> Signup and view all the answers

    What plays a key role in evaluating the signal quality in the operating room?

    <p>Amplifier gain</p> Signup and view all the answers

    Which method is NOT considered a modality for intraoperative monitoring?

    <p>Transcranial Doppler</p> Signup and view all the answers

    Signal-to-noise ratio (SNR) is calculated as the ratio of noise to signal in the operating room.

    <p>False</p> Signup and view all the answers

    What does EMG stand for?

    <p>Electromyography</p> Signup and view all the answers

    The measure of functional integrity in monitoring is called __________.

    <p>intraoperative monitoring</p> Signup and view all the answers

    Match the following modalities with their descriptions:

    <p>EEG = Records brain electrical activity EMG = Records muscle electrical activity SSEP = Measures sensory pathways TMS = Stimulates the cortex using magnetic fields</p> Signup and view all the answers

    Which type of evoked potential is associated with the auditory system?

    <p>BAEP</p> Signup and view all the answers

    Biological noise during monitoring is constant and does not vary based on what is being recorded.

    <p>False</p> Signup and view all the answers

    What does SNR stand for in the context of intraoperative monitoring?

    <p>Signal-to-Noise Ratio</p> Signup and view all the answers

    Cranial nerve stimulation can be part of __________ modulation during surgery.

    <p>electroneurography</p> Signup and view all the answers

    Which of the following is NOT a source of technical noise in the OR?

    <p>Biological functions</p> Signup and view all the answers

    Which part of the brain is primarily responsible for executing movements?

    <p>Motor cortex</p> Signup and view all the answers

    The corticospinal tract is exclusively responsible for slow and controlled movements.

    <p>False</p> Signup and view all the answers

    What type of reflexes are typically modulated by the extrapyramidal system?

    <p>Spinal reflex arcs</p> Signup and view all the answers

    The ________ is involved in the preparation and design of movements.

    <p>Supplementary motor area</p> Signup and view all the answers

    Match the following motor pathway components with their functionalities:

    <p>Primary motor cortex = Execution of movements Premotor cortex = Preparing movements Basal ganglia = Modulating reflexes Cerebellum = Coordination of movement</p> Signup and view all the answers

    Which of the following statements best describes upper motor neuron lesions?

    <p>They lead to increased reflexes and spasticity after several weeks.</p> Signup and view all the answers

    Lower motor neuron lesions are characterized by atrophy and flaccid muscle tone.

    <p>True</p> Signup and view all the answers

    What is the primary pathway involved in descending modulation of pain sensitivity?

    <p>Spinothalamic tract</p> Signup and view all the answers

    The ________ is responsible for processing complex information related to movements.

    <p>Association cortex</p> Signup and view all the answers

    Match the following pathways with their characteristics:

    <p>Corticospinal tract = Fast execution of movements Extrapyramidal system = Modulates spinal reflexes Afferent pathways = Sensory information transmission Descending pathways = Inhibitory modulation</p> Signup and view all the answers

    What is the primary electrophysiological assessment technique used for the peripheral nerve?

    <p>Sensory electroneurography</p> Signup and view all the answers

    The protopathic pathway assesses sharp pain and temperature sensations.

    <p>True</p> Signup and view all the answers

    What is assessed in the primary cortex of the somatosensory pathway?

    <p>Short-latency SEP</p> Signup and view all the answers

    The pathway responsible for proprioception and fine touch is known as the __________ pathway.

    <p>epicritic</p> Signup and view all the answers

    Match the following assessments with the corresponding pathway:

    <p>Sensory electroneurography = Peripheral nerve Short-latency SEP = Ascending tract Middle-latency SEP = Secondary/association cortex Event related EPs = Secondary/association cortex</p> Signup and view all the answers

    Which level of the nervous system is involved in the somatosensory assessment of the ascending tract?

    <p>Thalamus</p> Signup and view all the answers

    H-reflex is primarily used to assess muscle activity.

    <p>False</p> Signup and view all the answers

    Name one type of assessment used for evaluating the protopathic pathway.

    <p>Sensory electroneurography</p> Signup and view all the answers

    The __________ pathway is associated with the perception of fine touch and proprioception.

    <p>epicritic</p> Signup and view all the answers

    Which component is NOT primarily associated with the secondary/association cortex?

    <p>Auditory processing</p> Signup and view all the answers

    What is the highest intensity of current that a coil can generate during stimulation?

    <p>5,000 A</p> Signup and view all the answers

    The magnetic field generated by the coil penetrates the skin and skull with significant loss.

    <p>False</p> Signup and view all the answers

    What does the primary motor cortex represent?

    <p>Movements, not individual muscles.</p> Signup and view all the answers

    The _______ system is characterized as having monosynaptic connections to alpha motoneurons in primates.

    <p>corticospinal</p> Signup and view all the answers

    Match each component of the motor system with its function:

    <p>Primary motor cortex = Execution of voluntary movements Premotor cortex = Preparing and designing movements Extrapyramidal system = Coordination of reflexes and automatic movements Supplementary motor area = Planning of complex movements</p> Signup and view all the answers

    How do electrically evoked motor evoked potentials compare to magnetic motor evoked potentials?

    <p>They have shorter latency.</p> Signup and view all the answers

    The association cortex is primarily involved in motion execution only.

    <p>False</p> Signup and view all the answers

    What is the role of the basal ganglia in motor control?

    <p>Modulating and coordinating voluntary movements.</p> Signup and view all the answers

    What is the primary effect of preinnervation of the muscles?

    <p>Increases response</p> Signup and view all the answers

    The brain’s inverse flow direction of induced current aligns with the _______ of the coil during stimulation.

    <p>plane</p> Signup and view all the answers

    The early component of the Bereitschaftspotenzial occurs approximately 400 ms prior to a motor task execution.

    <p>False</p> Signup and view all the answers

    Match the following motor cortex areas with their functions:

    <p>Primary motor cortex = Direct execution of movements Premotor cortex = Preparation and planning of movements Supplementary motor area = Planning complex movements Association cortex = Higher level processing for complex movements</p> Signup and view all the answers

    What are the surface electrodes used for in motor evoked potentials?

    <p>Recording muscle responses</p> Signup and view all the answers

    The central motor conduction time is calculated as T1 minus ________.

    <p>T2</p> Signup and view all the answers

    Match the following components with their respective characteristics of motor evoked potentials:

    <p>Surface electrodes = Used for recording muscle responses Fig-8 coil = Allows for circumscribed cortical stimulation Spinal stimulation = Targets the distal part of the nerve root Preinnervation = Facilitates synaptic transmission</p> Signup and view all the answers

    Which of the following best describes the role of the contingent negative variation (CNV)?

    <p>The period between a warning and a go signal</p> Signup and view all the answers

    The amplitude of the Bereitschaftspotenzial is independent of the motor task being executed.

    <p>False</p> Signup and view all the answers

    Name the two components of the Bereitschaftspotenzial.

    <p>Early component and late component</p> Signup and view all the answers

    During motor evoked potential recording, the responding muscle depends on the coil position and the direction of ________.

    <p>current</p> Signup and view all the answers

    What is the typical signal-to-noise ratio (SNR) for Compound Muscle Action Potentials (CMAP)?

    <blockquote> <p>100:1</p> </blockquote> Signup and view all the answers

    All biological noise is deemed unmeaningful in evoked potential recordings.

    <p>False</p> Signup and view all the answers

    What kind of noise is associated with electrical devices during evoked potential recordings?

    <p>Technical noise</p> Signup and view all the answers

    The formula for signal-to-noise ratio (SNR) is SNR = Psignal/P_______.

    <p>noise</p> Signup and view all the answers

    Match the following evoked potentials with their typical SNR:

    <p>CMAP = &gt; 100:1 Sensory potentials = 1:2 – 10:1 MUPs = &gt; 100:1 EEG with EMG artefacts = &lt; 1:10</p> Signup and view all the answers

    Which of the following represents a potential SNR range for Sensory Potentials?

    <p>1:2 – 10:1</p> Signup and view all the answers

    Electrocerebral silence is characterized by a high SNR.

    <p>False</p> Signup and view all the answers

    Which frequency band in EEG is classified as Gamma?

    <blockquote> <p>31 Hz</p> </blockquote> Signup and view all the answers

    Alpha EEG is characterized by irregular rhythms that can differ by more than 1 Hz.

    <p>False</p> Signup and view all the answers

    What EEG frequency band is typically associated with sleep stages?

    <p>Theta</p> Signup and view all the answers

    The brain shows a permanent electric activity within distinct frequency bands, including Delta, Theta, Alpha, Beta, and __________.

    <p>Gamma</p> Signup and view all the answers

    Match the following EEG frequency bands with their characteristics:

    <p>Gamma = &gt; 31 Hz Beta = 13 – 30 Hz Alpha = 8 – 12 Hz Theta = 4 – 7 Hz Delta = &lt; 4 Hz</p> Signup and view all the answers

    What factors can influence the normal findings in an EEG?

    <p>Age and individual factors</p> Signup and view all the answers

    In bipolar montages, the source of a signal is localized better than in reference montages.

    <p>True</p> Signup and view all the answers

    What is a normal characteristic of alpha EEG?

    <p>Accentuated over the occipital and temporal lobe</p> Signup and view all the answers

    The degree of __________ can also affect normal EEG findings.

    <p>attention</p> Signup and view all the answers

    Which of the following is NOT considered a factor influencing EEG normal findings?

    <p>Personality traits</p> Signup and view all the answers

    What type of EEG finding is characterized by sharp waves and spikes?

    <p>Interictal activity</p> Signup and view all the answers

    Normal EEG findings are characterized by abnormal electrical patterns in the brain.

    <p>False</p> Signup and view all the answers

    Name one type of activity monitored during an ictal EEG period.

    <p>Seizure activity</p> Signup and view all the answers

    The EEG primarily records activity generated by __________ potentials in the uppermost layer of the cortex.

    <p>subsynaptic</p> Signup and view all the answers

    Match the following EEG frequency bands with their corresponding activities:

    <p>Delta = Deep sleep Theta = Light sleep and relaxation Alpha = Calm, restful state Beta = Alertness and active thinking</p> Signup and view all the answers

    Which of the following correctly describes epilepsy-related EEG findings?

    <p>Spike and wave patterns</p> Signup and view all the answers

    Spike waves on an EEG are considered a normal finding.

    <p>False</p> Signup and view all the answers

    What role do specific thalamic nuclei play in generating EEG signals?

    <p>Relay sensory inputs to the cortex</p> Signup and view all the answers

    Layer I of the cortex has a dense population of synapses on peripheral dendrites of the __________ cells.

    <p>cortical pyramid</p> Signup and view all the answers

    Match the following EEG activities with their definitions:

    <p>Ictal = During a seizure Interictal = Between seizures Normal = Typical brain activity Abnormal = Irregular patterns indicating issues</p> Signup and view all the answers

    Which EEG activity is primarily restored after eye closing?

    <p>Alpha activity</p> Signup and view all the answers

    Electrocerebral silence is a normal finding in EEG.

    <p>False</p> Signup and view all the answers

    What type of abnormal EEG finding could indicate elevated intracranial pressure?

    <p>Pathologically slowed EEG</p> Signup and view all the answers

    EEG is dominated by _____ and/or Delta activity when there are pathologically slowed findings.

    <p>Theta</p> Signup and view all the answers

    Match the following EEG findings with their associated characteristics:

    <p>Alpha activity = Blocked by eye opening Theta activity = Pathologically impaired consciousness Burst-suppression = Severe brain dysfunction Electrocerebral silence = Potential brain death diagnosis</p> Signup and view all the answers

    Which of the following is commonly observed during drowsiness or sleep?

    <p>Delta activity</p> Signup and view all the answers

    Focal abnormalities in EEG can indicate the presence of tumors.

    <p>True</p> Signup and view all the answers

    Name one condition that can lead to burst-suppression EEG.

    <p>Severe brain injury</p> Signup and view all the answers

    During periods of _____, you might observe beta activity exclusively in the EEG.

    <p>wakefulness</p> Signup and view all the answers

    Which of the following is the primary purpose of electroencephalography (EEG)?

    <p>To record the electrical activity of the brain</p> Signup and view all the answers

    Which EEG finding may indicate a drug-induced state?

    <p>Beta activity</p> Signup and view all the answers

    The first human EEG was recorded in 1945 by Hans Berger.

    <p>False</p> Signup and view all the answers

    What are the four anatomically defined points used in the International 10-20 system?

    <p>Nasion, Inion, Left ear, Right ear</p> Signup and view all the answers

    A normal EEG typically shows a range of frequency bands including delta, theta, alpha, and ______.

    <p>beta</p> Signup and view all the answers

    Match the EEG frequency bands with their associated states:

    <p>Delta = Deep sleep Theta = Light sleep or relaxation Alpha = Resting or calm state Beta = Active thinking or focus</p> Signup and view all the answers

    What does an abnormal EEG finding most commonly indicate?

    <p>Presence of epilepsy</p> Signup and view all the answers

    Clean, well-placed EEG electrodes should show interference from external sources.

    <p>False</p> Signup and view all the answers

    Define what EEG montages refer to.

    <p>Configurations used to connect electrodes for recording EEG signals.</p> Signup and view all the answers

    EEG stands for _______.

    <p>electroencephalography</p> Signup and view all the answers

    Which electrode positions in the International 10-20 system are designated with the letter 'P'?

    <p>Parietal</p> Signup and view all the answers

    What does EEG stand for?

    <p>Electroencephalography</p> Signup and view all the answers

    The first human EEG was recorded in 1924 by Hans Berger during a neurosurgical operation.

    <p>True</p> Signup and view all the answers

    What is the primary purpose of electroencephalography?

    <p>To record the electrical activity of the brain.</p> Signup and view all the answers

    The _______ of the head are used as reference points for electrode placement in the International 10-20 system.

    <p>anatomical landmarks</p> Signup and view all the answers

    Match the electrode position nomenclature with their meanings:

    <p>Fp = Frontoparietal F = Frontal C = Central P = Parietal O = Occipital T = Temporal</p> Signup and view all the answers

    Which of the following describes what EEG records?

    <p>Potential differences between pairs of two electrodes</p> Signup and view all the answers

    Electrode connections in EEG have no effect on the recordings obtained.

    <p>False</p> Signup and view all the answers

    What is the International 10-20 system used for?

    <p>To standardize electrode placement on the scalp for EEG.</p> Signup and view all the answers

    In EEG montages, the _______ montage records locations along the same axis.

    <p>longitudinal</p> Signup and view all the answers

    What are the four anatomical points used in the International 10-20 system?

    <p>Nasion, Inion, Left ear, Right ear</p> Signup and view all the answers

    Which EEG frequency band is classified as Gamma?

    <blockquote> <p>31 Hz</p> </blockquote> Signup and view all the answers

    Bipolar montages are generally less sensitive than reference montages in EEG recording.

    <p>False</p> Signup and view all the answers

    Name one factor that influences the normal EEG readings.

    <p>Age</p> Signup and view all the answers

    The EEG frequency band that ranges from 8 to 12 Hz is known as the ______ band.

    <p>Alpha</p> Signup and view all the answers

    Match the following EEG frequency bands to their ranges:

    <p>Gamma = &gt; 31 Hz Beta = 13 - 30 Hz Alpha = 8 - 12 Hz Theta = 4 - 7 Hz Delta = &lt; 4 Hz</p> Signup and view all the answers

    In which stage of sleep does rapid eye movement (REM) occur?

    <p>Stage 1</p> Signup and view all the answers

    Side differences in amplitude exceeding 50% are considered normal in alpha EEG findings.

    <p>False</p> Signup and view all the answers

    What is a primary advantage of using bipolar montages in EEG?

    <p>Better localization of signal sources</p> Signup and view all the answers

    EEG readings can be influenced heavily by ______ stimuli.

    <p>external</p> Signup and view all the answers

    Which of the following is NOT a factor affecting normal EEG?

    <p>Mood</p> Signup and view all the answers

    What type of EEG activity is identified as interictal epileptic activity?

    <p>Spikes/sharp waves</p> Signup and view all the answers

    Layer I of the cortex has the least population of synapses compared to other layers.

    <p>False</p> Signup and view all the answers

    What function does the ascending reticular activating system (ARAS) primarily serve?

    <p>Regulating consciousness and attention</p> Signup and view all the answers

    Electroencephalography (EEG) recordings are mainly generated by _______ potentials in the uppermost layer of the cortex.

    <p>subsynaptic</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Cortical afferents = Sources of sensory input to the cortex Primary cortex = The region responsible for initial sensory processing Association cortex = Integrates information from multiple sensory modalities Specific thalamic nuclei = Relay stations for sensory information</p> Signup and view all the answers

    What determines the potential differences at the scalp in EEG recordings?

    <p>The geometric relation of dipoles and recording electrodes.</p> Signup and view all the answers

    The orientation of a dipole remains the same regardless of its location in the brain.

    <p>False</p> Signup and view all the answers

    What is the relationship of specific thalamic nuclei to EEG generators?

    <p>They act as second relay stations for sensory information.</p> Signup and view all the answers

    The _______ is responsible for the biggest dipole with surface negativity perpendicular to the surface after activation of the unspecific thalamocortical projections.

    <p>EPSP</p> Signup and view all the answers

    Which layer of the cortex is primarily involved in generating EEG signals?

    <p>Layer I</p> Signup and view all the answers

    What is the primary characteristic of alpha EEG activity?

    <p>It is blocked by eye opening.</p> Signup and view all the answers

    Beta EEG activity is commonly seen during drowsiness or while sleeping.

    <p>True</p> Signup and view all the answers

    What type of abnormalities can indicate elevated intracranial pressure in EEG findings?

    <p>Pathologically slowed EEG</p> Signup and view all the answers

    Electrocerebral silence may be used to shorten waiting time in the diagnosis of __________.

    <p>brain death</p> Signup and view all the answers

    Match the abnormal EEG findings with their implications:

    <p>Electrocerebral silence = Possible brain death Burst-suppression = Severe brain dysfunction Focal abnormalities = Localized brain issues Pathologically slowed EEG = Elevated intracranial pressure</p> Signup and view all the answers

    What is a common artifact that can affect EEG results?

    <p>Poor electrode placement</p> Signup and view all the answers

    Theta or delta activity can increase during certain sleep stages without indicating pathology.

    <p>True</p> Signup and view all the answers

    State one potential cause of focal abnormalities in EEG findings.

    <p>Tumors</p> Signup and view all the answers

    A blockade in alpha EEG activity occurs predominantly during __________.

    <p>eye opening</p> Signup and view all the answers

    What can be indicated by circumscribed slowing in EEG readings?

    <p>Localized issues such as tumors or infarction</p> Signup and view all the answers

    Study Notes

    • Uses a neuronavigation system to precisely target specific brain regions for TMS stimulation
    • Nexstim is a leading company in navigated TMS

    Tractography

    • Uses MRI-based diffusion tensor imaging (DTI) to map white matter pathways in the brain
    • Allows visualization of nerve fiber tracts, providing insights into brain connectivity
    • DTI measures the movement of water molecules in the brain, revealing the orientation of nerve fibers

    Neuronavigation

    • Involves using a navigation system to visualize and target anatomical structures in the brain
    • Often used in conjunction with TMS and DTI for more precise interventions.
    • Allows for virtual planning and guidance during procedures

    Cardinal signs of Parkinson's disease

    • Akinesia/Bradykinesia
      • Start/Stop disturbance
      • Impaired facial expression
      • Micrography
      • Parkinsonian gait
    • Tremor
    • Rigidity
    • Postural instability

    Other symptoms:

    • Neuropsychiatric
    • Vegetative

    Parkinson's Disease - Therapy

    • First line: drugs (L-Dopa, Dopamine agonists)
    • In case of drug resistance: Deep Brain Stimulation (DBS)

    DBS: Targeting the optimal location

    • DBS electrodes record activity from surrounding neurons, which can be used to optimize DBS location
    • Raw data is filtered to get neuronal firing and local field potential
    • High-pass filtering results in neuronal firing
    • Low-pass filtering results in local field potential

    Parkinson's disease – DBS optimization with local field potentials

    • E0 is chosen as the optimal electrode location based on local field potential
    • Modern DBS systems record local field potential from multiple channels
    • LFP can be used for closed-loop stimulation (aDBS)

    Parkinson's disease: DBS effect on local field potentials

    • Phase amplitude coupling (PAC) can be used to analyze the relationship between neural activity in different frequency bands

    Parkinson's disease: DBS segmented stimulation

    • DBS can be modulated based on the phase of neural oscillations using segmented stimulation.

    Parkinson's disease: DBS – Adverse Effects

    • Infections
    • Hemorrhage
    • Speech arrest
    • Apathy
    • Hallucinations
    • Hypersexuality
    • Cognitive dysfunction
    • Depression
    • Euphoria

    Parkinson's disease: Avoiding DBS side effects

    • Single shot antibiotics
    • Electrophysiologically optimized placement of DBS electrodes
    • Closed loop stimulation
    • Electrode optimization (directional stimulation)

    Cerebellum

    • Vestibulocerebellum
      • Maintenance of posture and equilibrium
      • Maintenance of muscle tone
    • Spinocerebellum
      • Error correction, adjust posture
      • Smoothness and coordination of movements
    • Cerebrocerebellum
      • Planning and programming of movements
      • Coordination of complex movements
      • Sequence and precision of movements
      • Timing of movements

    Extrapyramidal system

    • All nuclei and tracts except the pyramidal system
    • Polysynaptic corticospinal projections
    • Cerebellum
    • Basal ganglia
    • Modulates spinal reflex arcs (usually inhibition)

    Basal ganglia

    • A group of subcortical nuclei at the base of the forebrain and the top of the midbrain
    • Associated with a variety of functions:
      • Control of voluntary movements
      • Procedural Learning
      • Habit learning
      • Conditional learning
      • Eye movements
      • Cognition
      • Emotion

    Basal Ganglia Circuit

    • Input: Striatum
    • Output: Globus pallidus interna (GPi) and substantia nigra pars reticularis (SNret)
    • Direct Pathway
      • Striatum -> SNret/GPi -> Thalamus (disinhibition = facilitation of thalamocortical projections)
    • Indirect Pathway
      • Striatum -> globus pallidus externa (GPe) -> subthalamic nucleus (STN) -> SNret/GPi -> Thalamus (inhibition of thalamocortical projections)

    Substantia nigra pars compacta

    • Dopaminergic projections to the striatum
    • D1 receptors in the striatum are excitatory
    • D2 receptors in the striatum are inhibitory

    Cortical stimulation

    • A triphasic response in basal ganglia output nuclei (SNret/GPi)
      • Increased activity after a delay (inhibition of thalamocortical projections)
      • Decreased activity (disinhibition, possibly associated with movement release)
      • Increased activity (inhibition of thalamocortical projections, stopping movement release)

    Motoric tasks

    • Initiation and termination of movements
    • Stabilization of movements
    • Stabilizing muscles at rest

    Parkinson's disease

    • Loss of dopaminergic neurons in the substantia nigra pars compacta
    • Cortical activation results in hyperactivity of SNret and inhibition of thalamocortical projections needed

    Basal Ganglia Diseases

    • Cardinal signs: akinesia/bradykinesia, tremor, rigidity, postural instability
    • Other symptoms: neuropsychiatric, vegetative
    • Parkinson's disease therapy:
      • First-line: drugs (L-Dopa, Dopaminagonists)
      • Drug resistance: Deep brain stimulation (DBS)

    Deep Brain Stimulation

    • Targets the subthalamic nucleus (STN)
    • DBS is implemented using implanted electrodes
    • Neurophysiological biomarkers can be recorded via extracellular microelectrodes or the DBS electrodes
    • Local field potentials (LFP):
      • Recorded by low-pass filtering raw data
      • Provide information on pre- and postsynaptic potentials (input)
      • Can be analyzed in the frequency domain and labeled according to EEG frequency bands
    • Neuronal firing:
      • Recorded by high-pass filtering raw data
      • Represent action potentials of local neurons (output)
    • DBS electrodes:
      • Record from a larger population of neurons in the surrounding area compared to microelectrodes

    DBS Optimization

    • Optimal DBS location: identified by analyzing neuron firing
    • Local field potentials (LFP): used to optimize DBS and identify optimal electrodes
    • Closed-loop stimulation (aDBS):
      • Adaptation of DBS that uses LFP recordings to adjust stimulation parameters
    • Phase Amplitude Coupling (PAC):
      • A phenomenon where the amplitude of oscillations in one frequency band is modulated by the phase of oscillations in another frequency band
    • Segmented stimulation:
      • DBS delivered in discrete, time-limited segments
      • Aims to optimize stimulation patterns based on specific motor tasks or neural activity

    Adverse Effects of DBS

    • Infection: can occur following surgery
    • Hemorrhage: can occur during electrode implantation
    • Speech arrest: can be caused by stimulation of areas near the speech centers
    • Apathy, hallucinations, hypersexuality, cognitive dysfunction, depression, and euphoria: can be side effects of stimulation

    Strategies to Minimize Adverse Effects

    • Single-shot antibiotics: help prevent infection
    • Electrophysiologically optimized placement of DBS electrodes: minimizes stimulation of areas associated with adverse effects
    • Closed-loop stimulation (aDBS):
      • Adapts stimulation based on real-time neural activity
      • May help mitigate side effects
    • Electrode optimization (directional stimulation):
      • Targets specific neural circuits
      • Can reduce stimulation of unintended areas

    Cerebellum

    • Vestibulocerebellum:
      • Maintains posture and equilibrium
      • Regulates muscle tone
    • Spinocerebellum:
      • Error correction
      • Postural adjustment
      • Smoothness and coordination of movements
    • Cerebrocerebellum:
      • Planning and programming of movements
      • Coordination of complex movements
      • Sequence and precision of movements
      • Timing of movements

    Motor Pathways

    • Extrapyramidal system:
      • Historically, all nuclei and tracts except the pyramidal system
      • Polysynaptic corticospinal projections:
      • Cerebellum
      • Basal ganglia
      • Modulates spinal reflex arcs
        • Primarily through inhibition

    Basal Ganglia

    • Group of subcortical nuclei:
      • Located at the base of the forebrain and top of the midbrain
      • Associated with a variety of functions
    • Functions:
      • Control of voluntary movements
      • Procedural learning
      • Habit learning
      • Conditional learning
      • Eye movements
      • Cognition
      • Emotion
    • Embedded in complex motor loops:
      • Tasks:
        • Initiation and termination of movements
        • Stabilization of movements
        • Stabilizing muscles at rest

    Basal Ganglia Pathways

    • Input from the cortex to basal ganglia:
      • Striatum (caudate nucleus & putamen)
    • Output to thalamus:
      • Globus pallidus interna (GPi)
      • Substantia nigra pars reticulata (SNret)
    • Direct pathway:
      • Striatum -> SNret/GPi -> Thalamus
      • “- x - = +“: Inhibition of SNret/GPi disinhibits thalamocortical projections, facilitating movement
    • Indirect pathway:
      • Striatum -> Globus pallidus externa (GPe) -> Subthalamic nucleus (STN) -> SNret/GPi -> Thalamus
      • Results in inhibition of thalamocortical projections: inhibits movement
    • Substantia nigra pars compacta (SNc):
      • Dopaminergic projections to the striatum: act as complex modulators
        • D1 receptors in the striatum: excitation
        • D2 receptors in the striatum: inhibition
        • Both pathways result in facilitation of thalamocortical impulse transmission
      • Loss of SNc neurons: is a hallmark of Parkinson's disease

    Cortical Stimulation of Basal Ganglia

    • Yields to a triphasic response in the basal ganglia output nuclei (SNret/GPi):
      • Phase 1 (Increased activity): inhibition of thalamocortical projections, stopping movement
      • Phase 2 (Decreased activity): disinhibition of thalamocortical projections, facilitating movement
      • Phase 3 (Increased activity): inhibition of thalamocortical projections, stopping movement

    Cortical Stimulation in Parkinson's Disease

    • Loss of dopaminergic neurons in substantia nigra pars compacta (SNc):
      • Results in hyperactivity of SNret and inhibition of thalamocortical projections
      • This inhibition prevents initiation of movement, leading to akinesia and bradykinesia, which are cardinal signs of Parkinson's disease.

    Intraoperative Monitoring Methods

    • Clinical, electrophysiological, hemodynamic, and metabolic methods to check functional integrity.
    • Electrophysiological modalities include electroneurography, electromyography (EMG), electroencephalography (EEG), and evoked potentials.

    Electroneurography

    • Measures compound muscle action potential (CMAP) latency and amplitude.
    • Cranial nerve stimulation: Stimulates nerves in the brain, brainstem, and peripheral nerves to assess integrity.
    • Measures nerve conduction velocity.

    Electromyography (EMG)

    • Spontaneous activity with acoustic feedback is monitored.
    • Mimic, eye, and laryngeal muscle activity can be assessed.

    Electroencephalography (EEG)

    • Monitors spontaneous brain activity.
    • Processed data can be depicted as Compressed Spectral Arrays (CSA) for analysis.

    Evoked Potentials

    • Somatosensory evoked potentials (SSEP): Stimulates peripheral nerves and records brain responses; phase reversal SEP is a specific type.
    • Brainstem auditory evoked potentials (BAEP): Stimulates auditory pathway and records brainstem responses.
    • Electrocochleography: Records cochlear responses.
    • Middle latency SEP and/or auditory evoked potentials (AEP): Records cortical responses.
    • Visual evoked potentials (VEP): Records visual pathway responses.

    Motor Evoked Potentials (MEP)

    • Magnetic Transcranial Magnetic Stimulation (TMS): Uses magnetic fields to stimulate the motor cortex.
    • Electric TMS: Uses electrical stimulation to stimulate the motor cortex.
    • Cortical stimulation: Directly stimulates the motor cortex.
    • White matter stimulation: Stimulates the descending motor pathways.
    • D-waves: Record presynaptic activity in the corticospinal tract.

    Signal-to-Noise Ratio (SNR) in the Operating Room (OR)

    • SNR = Psignal/Pnoise
    • Noise sources:
      • Technical Noise:
        • Line frequency (50/60Hz)
        • 100 Hz noise from electronic devices
        • Amplifier, electrode, and operating room equipment (e.g., high-frequency coagulators)
      • Biological Noise:
        • Depends on the signal being recorded.
        • Meaningful versus Unmeaningful signals need to be differentiated.

    Intraoperative Monitoring Methods

    • Functional integrity is checked using clinical, electrophysiological, hemodynamic, and metabolic methods.

    ### Intraoperative Monitoring Modalities

    • Electroneurography
      • Measures compound muscle action potential (CMAP) latency and amplitude.
      • Cranial nerve, brainstem, and peripheral nerve stimulation can be used.
      • Nerve conduction velocity can also be measured.
    • Electromyography (EMG)
      • Used to assess spontaneous muscle activity.
      • Acoustic feedback is provided for mimic, eye, and laryngeal muscles.
    • Electroencephalogram (EEG)
      • Records spontaneous brain activity.
      • Processed to create power spectra, which can be depicted as compressed spectral arrays (CSA).
    • Evoked Potentials
      • Somatosensory Evoked Potentials (SSEP)
        • Phase reversal SEP can be measured.
      • Brainstem Auditory Evoked Potentials (BAEP)
      • Electrocochleography
      • Middle Latency SEP (MLSEP) and Auditory Evoked Potentials (AEP)
      • Visual Evoked Potentials (VEP)
    • Motor Evoked Potentials
      • Magnetic Transcranial Magnetic Stimulation (TMS)
      • Electric TMS 
      • Cortical Stimulation
      • White Matter Stimulation
      • D-Waves

    ### Signal-to-Noise Ratio in the Operating Room

    • Signal-to-Noise Ratio (SNR) = Psignal/Pnoise
    • Noise Sources:
      • Technical Noise
        • Line frequency (50/60Hz)
        • 100Hz noise from electronic devices
        • Amplifier
        • Electrode
        • High frequency coagulators in the operating room
      • Biological Noise 
        • The type of recording will influence the biological noise.
        • Meaningful versus Unmeaningful signals.

    Somatosensory Pathway

    • The somatosensory pathway is responsible for transmitting sensory information from the body to the brain.
    • It involves several key structures, including the spinal cord, medulla oblongata, and thalamus.

    Electrophysiological Assessment of Somatosensory Pathway

    • Peripheral Nerve: Sensory electroneurography, H-reflex, and short-latency SEP can be used to assess the peripheral nerve portion of the somatosensory pathway.
    • Ascending Tract: Short-latency SEP is used to assess the ascending tract.
    • Primary Cortex: Short-latency SEP is used to assess the primary cortex.
    • Secondary/Association Cortex: Middle-latency SEP and event-related potentials are used to assess the secondary/association cortex.

    Protopathic Pathway

    • The protopathic pathway is responsible for transmitting pain, temperature, and crude touch sensations.
    • Specific stimulation techniques such as laser and thermic stimuli are not suitable for assessing the protopathic pathway due to their non-selective nature.

    Afferent Pathway Information Processing

    • Descending Modulation: Mainly inhibitory, it controls sensitivity of peripheral receptors, impacting the afferent pathway.
    • Alertness: Amplification, convergence/divergence, LCCS/ARAS-activation via the unspecific thalamus, and cortico-thalamo-cortical loops all contribute to alertness, influencing the afferent pathway.
    • Processing: Spatial and temporal resolution occur in primary and secondary cortex, integration of different inputs happens in tertiary cortex, and comparisons with memory contents further refine information processing in the afferent pathway.
    • Response: The afferent pathway prepares complex motor programs including flight, attack, grip, and speech based on processed sensory information.
    • Modulation: Habituation (excluding pain) and lateral inhibition at various levels further modify the sensory input. Descending input control also modulates the afferent pathway.

    Motor Systems

    • Motor Cortex: Consists of association cortex, supplementary motor area, premotor cortex, and primary motor cortex.
      • Association Cortex: Responsible for complex information processing to prepare for complex movements, including speech.
      • Supplementary Motor Area: Involved in preparing and designing movements.
      • Premotor Cortex: Also involved in preparing and designing movements.
      • Primary Motor Cortex: Executes movements, represented by the Homunculus.

    Motor Pathways

    • Corticospinal (Pyramidal) Tract: One of several motor systems, it's responsible for fast execution of movement programs, represented by the Homunculus, and involves monosynaptic connections to α-motoneurons in primates.
    • Extrapyramidal System: Includes all nuclei and tracts except the pyramidal system, utilizes polysynaptic cortico-spinal projections, involves cerebellum and basal ganglia, and modulates spinal reflex arcs, primarily through inhibition.

    Motor Pathway Lesions

    • Upper Motor Neuron Lesion: Results in paresis of movements, minor atrophy, initial flaccidity (spinal shock), spasticity after weeks, increased reflexes, and pathological reflexes.
    • Lower Motor Neuron Lesion: Causes paresis of muscles, atrophy, flaccid muscle tone, and loss of reflexes.

    Electrophysiological Assessment of Motor Systems

    • Bereitschaftspotenzial: A neurophysiological event that precedes voluntary movement.
    • Transcranial MEPs: Electric or magnetic stimulation of the motor cortex to elicit muscle contractions.
    • Spinal Magnetic Stimulation: Magnetic stimulation of the spinal cord to assess the integrity of motor pathways.
    • Motor Nerve Conduction: Measures the speed of nerve impulses along motor nerves.
    • F-Waves: Evoked muscle responses resulting from stimulation of a peripheral nerve and propagation of the impulse back to the spinal cord.
    • H-Reflex: A reflex elicited by electrical stimulation of a peripheral nerve, assessing spinal cord function.
    • EMG: Measures the electrical activity of muscles to assess their function.

    Technical notes

    • A coil generates a magnetic field perpendicular to its plane
    • Magnetic field penetrates skin and skull with minimal loss
    • Induced circular current in the brain has the same plane as the coil but opposite flow direction
    • Current intensity is highest under the innermost loops of the coil

    Motor Systems

    • Primary Motor Cortex (M1) is responsible for movement, not individual muscles, and represented by a homunculus
    • Premotor Cortex and Supplementary Motor Area plan and prepare movements
    • Association Cortex processes complex information to prepare complex movements, for example, speech

    Motor Pathways

    • Corticospinal (pyramidal) tract is a fast acting motor system responsible for movement execution
    • Homunculus represents movements, not individual muscles, and has a monosynaptic connection to α-motoneurons in primates
    • Extrapyramidal system is a polysynaptic cortico-spinal projection system including basal ganglia and cerebellum

    Motor Evoked Potential (MEP)

    • Stimulation of the motor cortex can be achieved through magnetic or electrical methods
    • Electrical stimulation is painful and stimulates different cellular elements
    • Electrically evoked MEPs have a shorter latency compared to magnetic MEPs in the same subject

    Recording MEPs

    • Surface electrodes record MEPs
    • The responding muscle depends on the coil position and current direction

    MEP Enhancement

    • Preinnervation of muscles facilitates synaptic transmission, increases response, and shortens latency

    MEP Spinal stimulation

    • Distal part of the nerve root or spinal nerve is typically stimulated
    • Central motor conduction time is calculated by subtracting the latency recorded at the spinal cord (T2) from the latency recorded at the brain (T1)

    Clinical Applications of MEPs

    • MEPs can be used to identify nerve compression based on changes in latency

    Fig-8 Coil

    • Tailored magnetic field for more circumscribed cortical stimulation
    • Suitable for navigated stimulation

    Bereitschaftspotenzial (Readiness Potential)

    • Negative potential generated before a motor task, consists of early and late components
    • Early component is generated by the supplementary motor area and premotor cortex (~ 1500 - 400 ms prior)
    • Late component is generated by the primary motor cortex (~ 400 - 0 ms prior)
    • Amplitude depends on the task (up to 20 µV)

    MEP and Bereitschaftspotenzial

    • Bereitschaftspotenzial reflects activity of the secondary motor cortex (SMA) and further association cortex
    • It is triggered internally (by movement) and recorded before the trigger

    Difference to Contingent Negative Variation (CNV)

    • CNV is a negative slow surface potential generated between a warning stimulus and an imperative ("go") stimulus.

    Signal-to-noise Ratio (SNR)

    • SNR is calculated as the power of the signal divided by the power of the noise.
    • Noise can be technical or biological.
    • Technical noise sources include line frequency (50/60Hz), 100Hz noise from electronic devices, amplifier, electrode, and high-frequency coagulators in the operating room.
    • Biological noise depends on the type of signal being recorded.
    • It is important to distinguish between meaningful and meaningless signals.

    Typical SNRs

    • Electroencephalogram (EEG)
      • Normal subjects typically have an SNR of 10:1 - 50:1.
      • SNR can be < 1:10 with Electromyographic (EMG) artifacts.
      • Electrocerebral silence has an SNR of 3:1.
    • Electromyography (EMG)
      • Spontaneous activity has an SNR of 5:1 - 10:1.
      • Motor unit potentials (MUPs) have an SNR of > 100:1.
      • Interference patterns have an SNR of > 100:1.
    • Evoked Potentials
      • Sensory evoked potentials (SEP) and visual evoked potentials (VEP) have an SNR of 1:2 – 1:20.
    • ElectroNeurography (ENG)
      • Compound muscle action potential (CMAP) has an SNR of > 100:1.
      • Sensory nerve action potentials have an SNR of 1:2 – 10:1.

    EEG - Normal Findings

    • Alpha - EEG is modulated in the form of a spindle and is blocked by eye opening but restored after eye closing.
    • Alpha - EEG is also known as the "My rhythm" and is strongest in the central region of the brain.
    • Beta EEG activity is present in all channels with alpha activity occasionally seen for a short time after eye closing.
    • Beta EEG activity can also be present in subjects who are drowsy or sleeping, strained or under the influence of pharmaceuticals.

    EEG - Abnormal Findings

    • Pathologically slowed EEG is dominated by Theta and/or Delta activity.
    • It may also indicate elevated intracranial pressure, pathologically impaired consciousness.
    • Theta or Delta activity increase during some sleep stages.
    • Alpha-coma is another potential finding indicating a slowed EEG.
    • Burst suppression is an abnormal EEG pattern.
    • Electrocerebral silence is a major finding.
    • Amplification of the recording, filter settings, and the presence of ECG artifacts all impact the validity of electrocerebral silence.
    • Electrocerebral silence may shorten waiting time in brain death diagnosis.

    EEG - Abnormal Findings: Focal Abnormalities

    • Focal abnormalities may be characterized by circumscribed slowing or epileptic activity in the EEG.
    • This type of abnormality can be present in a variety of conditions such as tumors, small bleedings, infarction, etc.

    EEG - Montages

    • Each montage has advantages and disadvantages.
    • Reference montages are more sensitive, especially if the distance between the active electrode and the reference is larger than in bipolar montages.
    • The source of a concrete signal is better localized in bipolar montages.
    • Localization in bipolar montages becomes difficult if the source is more widespread and affects the reference electrode.

    EEG - Frequency Bands

    • The brain exhibits continuous electrical activity.
    • EEG recordings display rhythmic activity within distinct frequency bands:
      • Gamma > 31 Hz
      • Beta 13 – 30 Hz
      • Alpha 8 – 12 Hz
      • Theta 4 – 7 Hz
      • Delta < 4 Hz
    • Note: The limits of the alpha- and beta bands may vary in the literature

    EEG - Normal Findings: Factors

    • The normal EEG is affected by a variety of factors:
      • Individual factors
      • Normal variants
      • The region from which it is derived
      • External stimuli
      • The degree of attention: awake or sleeping (5 stages - 4 without rapid eye movement and 1 with REM)
      • Age

    EEG - Normal Findings: Alpha - EEG

    • Alpha - EEG is very regular with a variation of no more than 1 Hz.
    • The frequency is individual-specific.
    • Activity is strongest over the occipital and temporal lobes.
    • Side differences in amplitude of less than 50% are normal.

    EEG - Abnormal Findings: Epileptic Activity

    • Epileptic activity can present in two ways:
      • Interictal: Spikes/sharp waves and Spike waves
      • Ictal: Seizures

    EEG - Generators: Cortical Afferents

    • Sensory input.
    • Specific thalamic nuclei: Second relay station.
    • Primary cortex.
    • Association cortex.
    • Unspecific thalamic nuclei: Widespread cortical projections.
    • Relation to the ascending reticular activating system (ARAS): Cortical inhibition.

    EEG - Generators: Relation to Cell Potentials

    • Layer I of the cortex has a dense population of synapses on peripheral dendrites of the cortical pyramid cells.
    • Excitatory postsynaptic potentials (EPSPs) induce a greater current than inhibitory postsynaptic potentials (IPSPs) or action potentials (APs).
    • EPSPs induce a bigger dipole with surface negativity perpendicular to the surface.
    • Smaller dipoles are present in adjacent regions following activation of the unspecific thalamo-cortical projections.
    • Potential differences at the scalp are determined by the geometric relation of the dipoles and the recording electrodes.

    EEG - Generators: The Cortex

    • Dipole orientation differs between the tip of a gyrus and the slopes of a sulcus.
    • Dipole orientation also differs between the slopes of the sulcus.

    EEG - Generators: The EEG

    • The EEG is generated by subsynaptic potentials in the uppermost layer (layer I) of the cortex.
    • Afferents in this layer are part of the ARAS which regulates consciousness and attention.

    Electroencephalography

    • Electroencephalography (EEG) records the electrical activity of the brain using multiple electrodes placed on the scalp.
    • The electroencephalogram is the recorded electrical activity of the brain.
    • A living brain always exhibits continuous electrical activity.
    • The first human EEG was recorded in 1924 by Hans Berger in Jena during a neurosurgical operation.

    Electrode Placement

    • The International 10-20-system is used to place electrodes.
    • Four anatomical points on the head serve as references for distance measurement:
      • Nasion
      • Inion
      • Left ear
      • Right ear.

    Electrode Placement: Nomenclature

    • The naming of electrodes is based on the following structure:
      • Region where the electrode is placed:
        • Fp – frontoparietal
        • F – frontal
        • C – central
        • P – parietal
        • O – occipital
        • T – temporal
        • A – auricular (ears)
      • Side:
        • Z – midline
        • Odd – left
        • Even - right

    EEG - What do we record?

    • The electrical activity of the brain under the electrodes.

    EEG - What do we Record?: Potential Differences

    • We are measuring potential differences between pairs of electrodes.

    EEG - What do we record?: Montages

    • The way we connect electrodes to amplifiers impacts the EEG recording.
    • There are two main types of montages:
      • Bipolar:
        • Longitudinal
        • Transversal
      • Reference:
        • Ipsilateral ear
        • Cz
        • ….

    Electroencephalography

    • Electroencephalography (EEG) is the technique to record electrical activity of the brain using electrodes placed on the scalp
    • EEG is used to detect brain activity, diagnose and monitor brain disorders, and guide brain surgery
    • The first human EEG was recorded in 1924 by Hans Berger in Jena during a neurosurgical operation
    • The electroencephalogram (EEG) is the recorded electrical activity of the brain
    • A living brain exhibits continuous electrical activity

    Electrode Placement

    • Electrodes are placed according to the International 10-20 system, which is based on distances between four anatomical points: nasion, inion, left ear, and right ear. Electrode positions are named based on the region and side:
      • Fp - frontoparietal
      • F - frontal
      • C - central
      • P - parietal
      • O - occipital
      • T - temporal
      • A - auricular (ears)
      • Z - midline
      • Odd - left
      • Even - right

    EEG Recordings

    • EEG captures potential differences between pairs of electrodes
    • The way electrodes are connected to amplifiers (channels) determines what is recorded
    • Common EEG montages include:
      • Bipolar: Longitudinal and transversal
      • Reference: Ipsilateral ear, Cz, average reference, Laplacian

    EEG Signal Analysis

    • Bipolar Montages: Show phase reversal, helpful in localizing the source of a signal
    • Reference Montages: More sensitive, especially for signals with large distances between the active electrode and the reference
    • Frequency Bands: EEG signal is analyzed based on frequency bands, each with a distinct range:
      • Gamma: > 31 Hz
      • Beta: 13 - 30 Hz
      • Alpha: 8 - 12 Hz
      • Theta: 4 - 7 Hz
      • Delta: < 4 Hz

    Normal EEG Findings

    • Normal EEG varies based on:
      • Individual factors
      • Normal variants
      • Region of the brain
      • External stimuli
      • Degree of attention (awake, asleep)
      • Age
    • Alpha EEG:
      • Regular, with a frequency range of less than 1 Hz
      • Individual specific frequency
      • Accentuated over the occipital and temporal lobes
      • Side differences in amplitude of less than 50% are normal
      • Often modulated in form of a spindle
      • Blocked by eye opening
      • Restored after eye closing
    • My - Rhythm: Occurs in the central region
    • Beta EEG:
      • Only beta activity in all channels
      • Alpha activity may be seen briefly after eye closing
      • Influenced by individual factors, drowsiness, sleep, strain, medication

    Abnormal EEG Findings

    • Pathologically Slowed EEG:
      • Dominated by Theta and/or Delta activity
      • Indicates elevated intracranial pressure or impaired consciousness
    • Burst - Suppression EEG: Characterized by bursts of high-amplitude activity followed by periods of silence
    • Electrocerebral Silence: Absence of any electrical activity, used to diagnose brain death
    • Focal Abnormalities: Circumscribed slowing or epileptic activity, can indicate:
      • Tumors
      • Small bleedings
      • Infarction
    • Epileptic Activity:
      • Interictal: Spikes/sharp waves, spike waves
      • Ictal: Episodes of high-amplitude activity, corresponding to seizures

    EEG Generators

    • Cortical Afferents:
      • Sensory input
      • Specific thalamic nuclei (second relay station)
      • Primary cortex
      • Association cortex
      • Unspecific thalamic nuclei (widespread cortical projections)
      • Ascending reticular activating system (ARAS) (regulates consciousness and attention)
      • Cortical inhibition

    Relation to Cell Potentials

    • Layer I of the cortex has a dense population of synapses on peripheral dendrites of cortical pyramid cells
    • EPSPs induce a greater current than IPSPs or APs, creating the biggest dipole with surface negativity perpendicular to the surface
    • Activated unspecific thalamocortical projections induce smaller dipoles to adjacent regions
    • Potential differences at the scalp are determined by the geometric relationship between dipoles and recording electrodes

    EEG and Cortical Anatomy

    • Dipole orientation differs between gyri and sulci, influencing EEG recordings
    • EEG is mainly generated by subsynaptic potentials in layer I of the cortex, where afferents of the ARAS are located

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    Description

    This quiz explores advanced techniques in neurology such as navigated TMS, tractography, and neuronavigation. Learn about how these methods use sophisticated imaging and targeting to enhance brain treatment and understanding. Test your knowledge on the impact of these technologies on brain connectivity and stimulation.

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