Neurology Flashcards

A 58-year-old man presents with progressive asymmetric parkinsonism, early postural instability, vertical supranuclear gaze palsy, and axial rigidity greater than appendicular rigidity. Levodopa provides minimal benefit. Which pathological finding is most characteristic of this condition?

Answer: Tau-positive neurofibrillary tangles and glial inclusions in the subthalamic nucleus and globus pallidus

This presentation is classic for Progressive Supranuclear Palsy (PSP). The pathological hallmark is 4-repeat tau accumulation forming neurofibrillary tangles and glial inclusions predominantly in the subthalamic nucleus, globus pallidus, substantia nigra, and brainstem. Unlike Parkinson's disease (Lewy bodies), PSP is a primary tauopathy. The vertical gaze palsy and early falls distinguish it from PD clinically.

A 34-year-old woman with relapsing-remitting MS on natalizumab for 30 months develops subacute cognitive decline and a new enhancing lesion on MRI with unusual "Swiss cheese" appearance. Her JC virus antibody index is 3.8. The MOST critical next step in management is:

Answer: Discontinue natalizumab and initiate plasma exchange to accelerate drug clearance

The clinical picture strongly suggests Progressive Multifocal Leukoencephalopathy (PML), a JC virus opportunistic infection associated with natalizumab use — especially with a JC antibody index >1.5 and >24 months of treatment. The immediate priority is discontinuing natalizumab and performing plasma exchange (PLEX) to rapidly clear the drug and restore immune surveillance. While CSF PCR confirms diagnosis, the high pre-test probability and risk of fatal PML-IRIS make drug cessation and PLEX the most critical intervention.

A 72-year-old woman presents with sudden-onset monocular visual loss lasting 10 minutes, now resolved. She has a carotid bruit. Duplex ultrasound shows 75% ipsilateral ICA stenosis. Which statement about antiplatelet and surgical management is MOST accurate?

Answer: Carotid endarterectomy is preferred over carotid artery stenting in symptomatic patients over 70 years of age with suitable anatomy

Current guidelines (AHA/ASA) recommend carotid endarterectomy (CEA) over carotid artery stenting (CAS) for symptomatic stenosis ≥70% in patients older than 70 years who are surgical candidates, largely based on CREST and ICSS trial data showing higher periprocedural stroke risk with CAS in elderly patients. CEA benefit is greatest when performed within 2 weeks of the index event, but benefit persists beyond 2 weeks. Dual antiplatelet therapy is not a substitute for revascularization in high-grade symptomatic stenosis.

A 45-year-old man presents with ascending weakness reaching the thighs over 4 days following a Campylobacter jejuni gastroenteritis 3 weeks prior. CSF shows albuminocytologic dissociation. Nerve conduction studies reveal prolonged distal motor latencies, reduced CMAP amplitudes, absent F-waves, and normal SNAP amplitudes. Which antibody is MOST specifically associated with the severe axonal variant of this condition that correlates with this organism?

Answer: Anti-GM1 and anti-GD1a IgG

C. jejuni infection is the most common identifiable antecedent of Guillain-Barré syndrome. The axonal variant (AMAN — Acute Motor Axonal Neuropathy) is strongly associated with anti-GM1 and anti-GD1a IgG antibodies through molecular mimicry with C. jejuni lipooligosaccharide. Anti-GQ1b is associated with Miller Fisher syndrome (ophthalmoplegia, ataxia, areflexia). Anti-GD1b correlates with sensory ataxic GBS. Anti-MAG is associated with IgM paraproteinemic neuropathy.

A 29-year-old woman with epilepsy presents for preconception counseling. She is seizure-free on valproate 1500 mg/day. She has tried lamotrigine previously, which failed due to rash. Which intervention has the STRONGEST evidence for reducing the risk of major congenital malformations in her future pregnancy?

Answer: Supplement with high-dose folic acid (4–5 mg/day) and attempt conversion to a safer AED before conception

Valproate carries the highest risk of major congenital malformations (~10%) and neurodevelopmental impairment of all commonly used AEDs. The evidence-based approach is to supplement with high-dose folic acid (4–5 mg/day, vs. standard 0.4–0.8 mg) AND attempt conversion to a less teratogenic AED (e.g., lamotrigine — if rechallenge with slower titration tolerated, or levetiracetam) before conception. Simply splitting valproate doses does not meaningfully reduce teratogenic risk. Aspirin has no role in this context.

A 66-year-old man presents with fluctuating cognition, vivid visual hallucinations of animals, and parkinsonism. He was given haloperidol by an emergency physician for agitation and developed profound rigidity and decreased consciousness within 24 hours. Which mechanism BEST explains his severe neuroleptic sensitivity reaction?

Answer: Blockade of D2 receptors in a nigrostriatal system already depleted of dopaminergic neurons

This is Dementia with Lewy Bodies (DLB). Patients with DLB have profound presynaptic dopaminergic deficiency in the striatum due to alpha-synuclein pathology. D2 receptor blockade by typical antipsychotics (like haloperidol) in an already critically dopamine-depleted system causes catastrophic worsening — severe parkinsonism, reduced consciousness, autonomic instability, and potentially fatal neuroleptic sensitivity in up to 50% of DLB patients. Atypical antipsychotics (quetiapine, clozapine) with low D2 affinity are used cautiously if necessary.