Podcast
Questions and Answers
What is a primary factor contributing to poor spatial resolution in scalp-recorded EEG?
What is a primary factor contributing to poor spatial resolution in scalp-recorded EEG?
Which imaging technique can enhance the accuracy of EEG data localization?
Which imaging technique can enhance the accuracy of EEG data localization?
Which of the following findings is NOT indicative of focal EEG patterns?
Which of the following findings is NOT indicative of focal EEG patterns?
What type of EEG pattern is characterized by focal theta–delta slow waves with preserved background activity?
What type of EEG pattern is characterized by focal theta–delta slow waves with preserved background activity?
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What happens to electrical activity as it travels from the cortex to the scalp?
What happens to electrical activity as it travels from the cortex to the scalp?
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Which of the following EEG findings indicates the presence of focal/unilateral epileptiform activity?
Which of the following EEG findings indicates the presence of focal/unilateral epileptiform activity?
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Which condition reflects an increase in theta–delta slow waves along with depression of basic background activity?
Which condition reflects an increase in theta–delta slow waves along with depression of basic background activity?
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In the context of EEG findings, what is a key characteristic of focal/unilateral amplitude depression?
In the context of EEG findings, what is a key characteristic of focal/unilateral amplitude depression?
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What is the term used for the focal amplitude accentuation resulting from a skull defect?
What is the term used for the focal amplitude accentuation resulting from a skull defect?
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Which lobe was NOT noted to have atrophy based on the MRI findings?
Which lobe was NOT noted to have atrophy based on the MRI findings?
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What type of activity showed consistent depression over the left hemisphere in the EEG?
What type of activity showed consistent depression over the left hemisphere in the EEG?
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What might a 'spiky'-appearing beta rhythm indicate if it is larger or more widespread than typical breach rhythm?
What might a 'spiky'-appearing beta rhythm indicate if it is larger or more widespread than typical breach rhythm?
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Following a craniotomy, which EEG activity is most likely to enhance near the site of the skull defect?
Following a craniotomy, which EEG activity is most likely to enhance near the site of the skull defect?
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What EEG finding was observed in a patient with acute aphasia and right-sided weakness due to a left middle cerebral artery infarct?
What EEG finding was observed in a patient with acute aphasia and right-sided weakness due to a left middle cerebral artery infarct?
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What condition was mentioned in relation to the patient who had a history of closed head injury?
What condition was mentioned in relation to the patient who had a history of closed head injury?
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Which type of EEG wave activity is characterized by a significant enhancement often noted as 'spiky'?
Which type of EEG wave activity is characterized by a significant enhancement often noted as 'spiky'?
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Which statement accurately describes the EEG characteristics related to the right subdural hematoma case?
Which statement accurately describes the EEG characteristics related to the right subdural hematoma case?
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The EEG changes noted in the patient primarily affected which hemisphere?
The EEG changes noted in the patient primarily affected which hemisphere?
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What was the primary EEG observation in the patient with a history of partial complex seizures due to an arachnoid cystic lesion in the right frontal lobe?
What was the primary EEG observation in the patient with a history of partial complex seizures due to an arachnoid cystic lesion in the right frontal lobe?
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In the case of the 62-year-old woman who experienced a left middle cerebral artery infarct, what was significant about the EEG findings?
In the case of the 62-year-old woman who experienced a left middle cerebral artery infarct, what was significant about the EEG findings?
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Which of the following best describes the alpha rhythm findings in the patient with right-sided weakness from the left middle cerebral artery infarct?
Which of the following best describes the alpha rhythm findings in the patient with right-sided weakness from the left middle cerebral artery infarct?
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What distinguishes the EEG findings of the 27-year-old woman with partial complex seizures from those in other cases?
What distinguishes the EEG findings of the 27-year-old woman with partial complex seizures from those in other cases?
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What condition was associated with the EEG showing increased amplitude of background activity in the case of the 49-year-old man?
What condition was associated with the EEG showing increased amplitude of background activity in the case of the 49-year-old man?
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Which EEG phenomenon was absent in the right hemisphere of the patient with a left middle cerebral artery infarct?
Which EEG phenomenon was absent in the right hemisphere of the patient with a left middle cerebral artery infarct?
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What is the relationship between IRDA and infratentorial lesions?
What is the relationship between IRDA and infratentorial lesions?
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How does IRDA differ from ADA in terms of responsiveness?
How does IRDA differ from ADA in terms of responsiveness?
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In which situations is focal or lateralized IRDA most likely to indicate potential seizure activity?
In which situations is focal or lateralized IRDA most likely to indicate potential seizure activity?
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Which type of tumor is more likely to show epileptiform activity?
Which type of tumor is more likely to show epileptiform activity?
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What is the likelihood of focal spike activity occurring immediately after a cerebrovascular accident (CVA)?
What is the likelihood of focal spike activity occurring immediately after a cerebrovascular accident (CVA)?
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What type of lesions are associated with a higher occurrence of spike-wave discharges?
What type of lesions are associated with a higher occurrence of spike-wave discharges?
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What amplitude characteristic is associated with IRDA in supratentorial lesions?
What amplitude characteristic is associated with IRDA in supratentorial lesions?
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Which of the following statements about focal spikes is true?
Which of the following statements about focal spikes is true?
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What is commonly associated with the appearance of PLEDs in patients with CVA?
What is commonly associated with the appearance of PLEDs in patients with CVA?
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In which condition are PLEDs most commonly seen?
In which condition are PLEDs most commonly seen?
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What feature characterizes the EEG discharges seen in PLEDs/LPDs?
What feature characterizes the EEG discharges seen in PLEDs/LPDs?
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What is the typical duration before PLEDs disappear after an acute infarction?
What is the typical duration before PLEDs disappear after an acute infarction?
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Which of the following terms is most closely related to the evolution of PLEDs in herpes encephalitis?
Which of the following terms is most closely related to the evolution of PLEDs in herpes encephalitis?
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What is the general capability of EEG in determining the exact localization of a lesion?
What is the general capability of EEG in determining the exact localization of a lesion?
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Which of the following conditions would NOT likely result in the appearance of PLEDs?
Which of the following conditions would NOT likely result in the appearance of PLEDs?
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What factors contribute to the development of PLEDs in patients with impaired consciousness due to acute hemispheric lesions?
What factors contribute to the development of PLEDs in patients with impaired consciousness due to acute hemispheric lesions?
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Study Notes
EEG and Spatial Resolution Issues
- Poor spatial resolution in scalp-recorded EEG is influenced by volume conductors: cerebrospinal fluid (CSF), dura mater, skull, and scalp.
- Electrical signals are attenuated and distorted by the time they reach the scalp, impacting the accuracy of EEG readings.
- Combining EEG data with MRI enhances anatomical localization accuracy.
Techniques for Enhanced EEG Analysis
- Magnetoencephalography (MEG) provides a more precise anatomical assessment of electrical sources in the brain compared to EEG.
- Focal EEG findings can indicate various neurological conditions, with key presentations including:
- Amplitude depression or slowing of background activity (alpha, beta waves) without increased theta-delta slow waves.
- Amplitude depression or slowing associated with an increase in theta-delta slow waves.
- Focal theta-delta slow waves with preserved basic background activity.
- Focal enhancement of background activity, potentially alongside slow waves.
- Focal or unilateral epileptiform activity, with or without associated slow waves.
Clinical Examples of Focal EEG Findings
- EEG in a 6-year-old with focal seizures showed alpha rhythm depression over the right hemisphere without significant focal delta-theta slow waves.
- A 62-year-old woman with acute aphasia exhibited decreased background activity and continuous polymorphic delta activity in the left hemisphere.
- In a 27-year-old woman, EEG revealed polymorphic delta from the right temporal region while maintaining symmetric background alpha rhythm.
- A patient with a right subdural hematoma presented increased amplitude of background activity and polymorphic delta slow waves in the right hemisphere.
Breach Rhythm and EEG Artefacts
- Skull defects from surgeries can cause local enhancement of EEG activity (termed "breach rhythm"), particularly affecting beta rhythm.
- “Spiky”-appearing activity in EEG may be misidentified; true spikes differ from breach rhythm spikes by exhibiting wider spread.
Intermittent Rhythmic Delta Activity (IRDA)
- Typically appears in metabolic and toxic encephalopathy; can also present in infratentorial lesions and may exhibit bilateral symmetry.
- Asymmetrical IRDA might indicate focal structural lesions, with characteristics such as augmentation during eye closure or hyperventilation.
Focal Epileptiform Activity
- Cortical scarring from injuries or lesions frequently leads to epileptiform activity.
- Spike or spike-wave discharges are most common in slowly progressive lesions, like low-grade cerebral tumors (astrocytoma).
- Focal spikes are less prevalent immediately after cerebrovascular accidents (CVAs), often emerging months later.
Periodic Lateralized Epileptiform Discharges (PLEDs)
- Seen in cases of significant hemispheric lesions, including massive hemorrhages or infarctions, particularly in patients with altered consciousness.
- PLEDs may evolve in conditions like herpes encephalitis, potentially transforming into bilateral independent periodic discharges (BiPLEDs).
Localization Challenges in EEG
- EEG is limited in accurately determining the specific location of a brain lesion; localization is generally confined to left/right and anterior/posterior quadrants.
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Description
This quiz explores the factors affecting the spatial resolution of scalp-recorded EEG, particularly the role of volume conductors like CSF, dura, skull, and scalp. Understand how these elements impact the distortion and attenuation of electrical signals from the cortex to the scalp.
