Brain Imaging Techniques

• X-ray: Shoots a beam of X-ray light; tissue absorption varies with thickness, captured on photo.
• X-ray limitations: Light is blocked by bone, limiting visibility of brain tissue.
• Cerebral angiography: X-ray with contrast agent (iodine) to highlight arteries/veins for identifying blockages/hemorrhaging.
• CT scanning: Creates 3D images from multiple X-ray angles via computer reconstruction.
• CT scanning: Useful for showing differences between liquid and brain tissue, identifies structural damage.
• CT limitations: Differentiates solid vs. fluid but not gray vs. white matter; superseded by MRI.
• MRI: Measures brain matter using electron magnetic alignment and supercooled magnets, based on CT reconstruction principles.
• MRI vs. CT: MRI is safer due to no radiation and provides more detailed images than CT.
• DTI (diffusion tensor imaging): Detects water molecule movement in white matter for connectivity measurement.
• DTI: Used for individuals with white matter damage without causing further harm to other brain regions.
• Adrian Owen: Employs fMRI to assist individuals with severe brain damage or those in comas to communicate.
• EEG and uses: Measures overall brain activity via electrical signals.
• EEG and uses: Useful in assessing brain death, sleep disorders, and is critical for measuring epilepsy.
• Overlay plot: Overlays structural MRIs of individuals with similar damage to identify common areas and related symptoms.
• EEG patterns - Awake: High frequency, low amplitude (not synchronized).
• EEG patterns - Sleep: Low frequency, high amplitude (synchronized).
• Structural imaging: X-ray, CT, Angiography, MRI, DTI.
• Functional imaging: PET, EEG, FMRI, and EFMRI.
• Heavy metal brain: Resting state differences found in cingulate cortex between heavy metal and classical music listeners.
• Heavy metal brain: Motor cortex differences (drugs and suicide speculated).
• Neuroimaging principle: Drawing conclusions should not be based solely on neuroimaging.

GCS (Glasgow Coma Scale)

• Used to assess consciousness level after acute brain injury.
• Assesses eye movement (1-4), verbal response (1-5), and motor response (1-6) separately.
• Best Scores: spontaneous eye movement, oriented verbal response, obeys motor commands.

Neuro exam vs. neuroimaging

• Neuroimaging: Structural imaging to understand biological structure.
• Neuro examination: Assesses functional aspects of the brain to understand injury symptoms.
• Neurological exams: Conducted following trauma/stroke, suspected neurodegeneration, or neurotoxin exposure.
• Neurological exam localization: It is hard to distinguish the location of neurological damage in certain brain regions.
• Internal capsule: White matter tract connecting brainstem (thalamus) to cortex (cortical thalamic loop), involving sensory & motor functions.
• General steps in neuroexam: Patient history, cranial nerve testing, motor reflexes, somatosensory function, movement coordination, mental status.

Components of patient history

• Age: Brain function naturally declines with age.
• Education: Higher education correlates with less brain decline.
• Handedness: Language dominance is usually in the left hemisphere, except in 25% of left-handed individuals (bilateral).
• Medical history: surgery anesthesia, medications, etc.
• Drug use: can change brain function
• Family history: any brain diseases in family?
• General disease progress: is it acute or progressive?

12 cranial nerves

• Olfactory (I): Sensory - smell.
• Optic (II): Sensory - sight.
• Oculomotor (III): Motor - eye & eyelid movement.
• Trochlear (IV): Motor - eye movement.
• Trigeminal (V): Both - face sense and jaw movement.
• Abducens (VI): Motor - eye movement.
• Facial (VII): Both - taste & facial sensation, facial expression
• Vestibulocochlear (VIII): Sensory - sound and balance.
• Glossopharyngeal (IX): Both - taste, posterior tongue, pharynx, and speech.
• Vagus (X): Both - outer ear canal, heart, lungs, viscera, speech.
• Accessory (XI): Motor - head and shoulder rotations.
• Hypoglossal (XII): Motor - tongue movement.
• Cribiform plate of ethmoid ridge: Holes in the skull that olfactory nerves pass through.
• Optical Fundus: Inside the back of the eye; related to eye pressure and POV problems.
• Papilledema: Swelling of the optic disc.
• Nystagmus: Involuntary eye movements.
• Ptosis: Severe drooping of one eye.
• Nerve 1 (Olfactory): Tests sensory function for smell using strong scents like coffee or cinnamon.
• Nerve 2 (Optic): Tests vision using Snell chart, vision test, fundus for intercranial pressure, and papilledema. standard FOV
• Nerve 3 (Oculomotor): Tests eyeball movement, asymmetries, nystagmus and ptosis evaluations.
• Nerve 4 (Trochlear): Tests eyeball movement and asymmetries.
• Nerve 5 (Trigeminal): Assesses facial sensation in 3 portions and jaw muscle movement using resistance and sensation tests.
• Nerve 6 (Abducens): Tests eye movement, asymmetries, and assesses for nystagmus and ptosis.
• Nerve 7 (Facial): Tests facial expressions, asymmetries; problems indicate Bells Palsy.
• Nerve 8 (Vestibulocochlear): Tests hearing and vestibular senses via tuning fork, whispering, and Romberg test.
• Bells Palsy: Damage to nerve 7, causes one side of the face to droop, usually goes away randomly
• Nerve 9 (Glossopharyngeal): Motor function - moving tongue/pharynx; Sensory function - inner tongue sensation; tested via cough, speech, swallow.
• Nerve 10 (Vagus): Sensory function - autonomic heart/stomach function, gag reflex/swallowing; Motor function - voice, heart/stomach control; tested via swallowing, speech, gag reflex symmetry.
• Nerve 11 (Accessory): Tests head, neck, and shoulder movement via resistance and shoulder shrug.
• Nerve 12 (Hypoglossal): Assesses tongue movement and lateral movement asymmetries.
• Neuroexam motor functions: Assess for asymmetries and muscle atrophies, which are key indicators.
• Upper motor neuron: Found in brain/spinal cord, controls major movements; damage causes hyperreflexia and muscle spasms
• Lower motor neuron: Runs from spinal cord to muscles, handling reflexes/coordination, damage causing Hyporeflexia/muscle sagging.
• Descending inhibition: Upper motor neurons inhibit unnecessary signals for coordinated movement. Damage release inhibition causes hyperreflexia.
• Neuron damage: Overall issues include problems with control, weakness, and coordination.

Sensory and Coordination Exams

• Sensory function exam: Tests pain, proprioception, and sensory processing.
• Sensory issues: Astereognosis, Agraphesthesia indicate potential cortex damage.
• Astereognosis: Inability to recognize objects by touch (texture, shape, size).
• Agraphesthesia: Inability to recognize symbols, letters or numbers traced on the skin.
• Coordination exam: Assessed via heel-to-shin and Romberg tests.
• Heel-to-shin test: Rapid leg movement from heel to shin.
• Heel-to-shin test: Issues suggest cerebellum or coordination problems.
• Romberg test: Assesses balance with eyes closed, revealing vestibular or cerebellum issues.

MSE (Mental Status Exam)

• Tested sections: Attention, orientation, language, memory, visuospatial function, executive function.
• Attention and orientation test: Assesses awareness by asking patients whereabouts, time, spelling backward, counting backward.
• Attention and orientation test: Involves cortical regions or high subcortical region (telencephalon).
• Attention and orientation test: Damage may be concentrated or diffuse
• Attentional problems: Contralateral neglect/hemi neglect, anosognosia.
• Contralateral neglect: Inability to perceive one side (usually left), due to impaired sensory processing or attention commonly damage to parietal lobe; assessed by drawing a clock.
• Anosognosia: Patient's denial of disorder or dysfunction.
• Language tests: Assesses fluency (pausing/skipping words), naming objects, repetition, prosody (intonation/emphasis), comprehension, reading, writing, praxis.
• Praxis and apraxia: Praxis is executing motor act on verbal command; apraxia is inability to perform motor actions on command.
• Language problems: Encompass aphasia, alexia, and agraphia from left hemisphere damage.
• Aphasia: Fluent (Wernicke's - word salad), non-fluent (Broca's - no speech), or global (both).
• Alexia: Inability to read or understand words.
• Agraphia: Problems with writing, inability to write.
• Memory tests assessment: Digit span, pointing span, factual knowledge recall.
• Memory tests regions: Involves hippocampus, temporal structures, thalamus, basal forebrain.
• Visuospatial tests measures: Line cancellation, geometric design copying, line orientation judgment, recognition of objects or faces.
• Visuospatial problems: Anogsia, propagnosia from temporal lobe damage.
• Agnosia: Inability to recognize objects.
• Agnosia: Sensory info reaches the brain but can't find the meaning
• Prosopagnosia: Inability to recognize faces related to fusiform gyrus.
• Executive function tests: Cognitive abilities assessment.
• Executive function: Ability to be flexible and have self control.
• Executive function: Judgement tests (correct decision making), verbal fluency (listing items), Luria 3-step (consecutive movements).