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Neurology USMLE Review

Sep 16, 2025

Overview

This lecture reviewed high-yield neurology concepts for the USMLE, focusing on brain pathologies, cranial nerve lesions, dementia, neurocutaneous syndromes, and test-taking strategies.

Intracranial Hematomas & Hemorrhages

  • Epidural hematoma: associated with trauma, lucid interval (“talk and die”), middle meningeal artery rupture, lens-shaped on CT.
  • Subdural hematoma: slow onset, bridging vein rupture, crescent-shaped on CT; risk increased in elderly, alcoholics, shaken infants.
  • Subarachnoid hemorrhage: sudden “thunderclap” headache, often due to berry aneurysm (esp. with PKD), blood in CSF, risk of delayed vasospasm.
  • Charcot-Bouchard aneurysms: hypertensive patients, affect deep brain structures (basal ganglia, thalamus), present gradually.

Intracranial Pressure & Herniation

  • Increased ICP presents with Cushing’s triad: hypertension, bradycardia, irregular respirations.
  • Hyperventilation lowers COâ‚‚, causing cerebral vasoconstriction and lower ICP.
  • Uncal (transtentorial) herniation compresses CN III (oculomotor), causing blown pupil (dilated, unreactive), down-and-out eye.

Cranial Nerve Lesions

  • CN I (olfactory): anosmia, CSF rhinorrhea with cribriform plate fracture.
  • CN II (optic): loss of afferent limb of pupil reflex, optic neuritis in MS.
  • CN III palsy: “down and out” eye, pupil dilation; commonly compressed by PCA aneurysm.
  • CN IV (trochlear): difficulty looking down stairs, head tilt away from lesion.
  • CN V (trigeminal): facial sensation, chewing; V1 corneal reflex, V3 jaw deviation.
  • CN VI (abducens): impaired lateral eye movement, affected in cavernous sinus thrombosis.
  • CN VII (facial): Bell’s palsy, loss of taste anterior 2/3 tongue, hyperacusis, HSV/Lyme disease causes.
  • CN VIII (vestibulocochlear): sensorineural hearing loss, vestibular schwannoma in NF2.
  • CN IX (glossopharyngeal): loss of posterior 1/3 taste, carotid sinus/gag reflex.
  • CN X (vagus): palate elevation, uvula deviates away from lesion.
  • CN XI (accessory): shoulder droop (trapezius), head turn weakness (sternocleidomastoid).
  • CN XII (hypoglossal): tongue deviation toward lesion.

Multiple Sclerosis

  • Young women with focal deficits; autoimmune CNS demyelination (oligodendrocytes).
  • MRI: periventricular plaques; CSF: oligoclonal bands.
  • INO: MLF demyelination, impaired adduction.
  • Optic neuritis: afferent pupillary defect, color vision loss.

Dementia & Neurodegenerative Disorders

  • Alzheimer’s: memory loss, impaired ADLs, neurofibrillary tangles (tau), amyloid plaques, APP gene (chromosome 21).
  • Frontotemporal dementia (Pick’s): behavioral changes, frontal/temporal atrophy, tau inclusions.
  • Lewy body dementia: parkinsonism, hallucinations, alpha-synuclein.
  • Parkinson’s disease: resting tremor, bradykinesia, substantia nigra dopamine loss.
  • Huntington’s disease: chorea, psychiatric symptoms, caudate atrophy, CAG repeat, anticipation.

Trinucleotide Repeat Disorders

  • Huntington’s: CAG.
  • Friedreich’s ataxia: GAA.
  • Myotonic dystrophy: CTG.
  • Fragile X: CGG.

Neurocutaneous Syndromes

  • Tuberous sclerosis: seizures, ash-leaf spots (hypopigmented), cardiac rhabdomyoma, renal angiomyolipoma.
  • Neurofibromatosis: cafĂ©-au-lait spots (NF1), Lisch nodules, optic glioma, acoustic schwannoma (NF2).
  • Sturge-Weber: port-wine stain, leptomeningeal angiomas, tram-track calcifications.
  • von Hippel-Lindau: hemangioblastomas, renal cysts, pheochromocytoma.
  • Ataxia-telangiectasia: telangiectasia, ataxia, IgA deficiency, DNA repair defect.

Brain Tumors

  • Adults (supratentorial): metastases, glioblastoma, meningioma, schwannoma.
  • Children (infratentorial): pilocytic astrocytoma (Rosenthal fibers), medulloblastoma (Homer Wright rosettes, drop mets), ependymoma.
  • Meningioma: psammoma bodies, ER+.
  • Glioblastoma: midline crossing, aggressive.
  • Schwannoma: CN VIII, bilateral in NF2.

Stroke Syndromes

  • Anterior cerebral artery: contralateral leg weakness/sensory loss.
  • Middle cerebral artery: contralateral face/arm weakness, aphasia (dominant), neglect (nondominant).
  • Posterior cerebral artery: contralateral homonymous hemianopsia with macular sparing.
  • PICA stroke: lateral medullary (Wallenberg) syndrome — ipsilateral face, contralateral body sensory loss, hoarseness, dysphagia, ataxia.
  • AICA stroke: lateral pontine syndrome — facial droop, hearing loss.

Key Terms & Definitions

  • Epidural hematoma — Arterial bleed between skull and dura, often middle meningeal artery.
  • Subdural hematoma — Venous bleed between dura and arachnoid from bridging veins.
  • Uncal herniation — Medial temporal lobe displacement compressing CN III.
  • Cushing’s triad — Hypertension, bradycardia, irregular respiration indicating high ICP.
  • Oligoclonal bands — IgG in CSF, marker for MS.
  • Tau protein — Microtubule-associated protein in Alzheimer’s and Picks.
  • Psammoma body — Concentric calcified structure in tumors (e.g., meningioma).
  • Homunculus — Somatotopic brain map, lateral (MCA) to medial (ACA).
  • Trinucleotide repeat — DNA sequence repeating three nucleotides, causing genetic diseases.

Action Items / Next Steps

  • Review lecture slides and linked resources (YouTube, First Aid outline, GOLIAN course).
  • Practice identifying key patterns in stroke and cranial nerve syndromes.
  • Schedule time to review brain imaging and neuroanatomy.
  • Read about neurocutaneous disorders and high-yield pathologies in a systematic organ-based manner.
  • Consider using productivity tools like Notion for study scheduling.

Full transcript