MD Central Nervous System Disorders 2 — Questions and Answers
Question 1: A 45-year-old man presents with sudden onset of thunderclap headache reaching maximal intensity within seconds. CT head is negative. What is the next best step?
- Discharge with analgesics
- Lumbar puncture for xanthochromia (Correct answer)
- MRI brain with contrast
- Start sumatriptan
Correct answer: Lumbar puncture for xanthochromia
A negative CT with thunderclap headache requires lumbar puncture to detect xanthochromia, indicating subarachnoid hemorrhage.
Question 2: Which demyelinating disease is characterized by optic neuritis, transverse myelitis, and area postrema syndrome, with seropositivity for AQP4-IgG?
- Multiple sclerosis
- Neuromyelitis optica spectrum disorder (Correct answer)
- Acute disseminated encephalomyelitis
- Clinically isolated syndrome
Correct answer: Neuromyelitis optica spectrum disorder
AQP4-IgG (anti-aquaporin-4) antibodies are the hallmark of neuromyelitis optica spectrum disorder (NMOSD).
Question 3: A 70-year-old presents with progressive gait instability, urinary incontinence, and cognitive decline. MRI shows enlarged ventricles disproportionate to sulcal atrophy. What is the diagnosis?
- Alzheimer dementia
- Normal pressure hydrocephalus (Correct answer)
- Lewy body dementia
- Vascular dementia
Correct answer: Normal pressure hydrocephalus
The classic triad of gait apraxia, urinary incontinence, and dementia with ventriculomegaly suggests normal pressure hydrocephalus.
Question 4: A patient develops ascending paralysis 2 weeks after a GI infection with Campylobacter jejuni. CSF shows albuminocytologic dissociation. Which antibody is associated with this variant?
- Anti-GQ1b
- Anti-GM1 (Correct answer)
- Anti-GD1b
- Anti-MAG
Correct answer: Anti-GM1
Anti-GM1 antibodies are associated with the acute motor axonal neuropathy (AMAN) variant of Guillain-Barré syndrome linked to Campylobacter.
Question 5: Which feature best distinguishes a Todd's paralysis from an acute ischemic stroke?
- Presence of headache
- Gradual resolution over minutes to hours after a seizure (Correct answer)
- Elevated blood pressure
- Age of the patient
Correct answer: Gradual resolution over minutes to hours after a seizure
Todd's paralysis is postictal focal weakness that resolves spontaneously within minutes to hours following a seizure.
Question 6: A 55-year-old with HIV presents with focal neurological deficits. MRI shows multiple ring-enhancing lesions. Toxoplasma serology is negative. What diagnosis must be excluded?
- Bacterial brain abscess
- Primary CNS lymphoma (Correct answer)
- Glioblastoma multiforme
- Metastatic carcinoma
Correct answer: Primary CNS lymphoma
In HIV patients with negative toxoplasma serology, primary CNS lymphoma is the leading differential for ring-enhancing lesions.
Question 7: A 30-year-old woman presents with intermittent diplopia, ptosis worsening through the day, and proximal limb weakness. Ice pack test improves ptosis. What antibody should be ordered first?
- Anti-MuSK
- Anti-AChR (Correct answer)
- Anti-voltage-gated calcium channel
- Anti-LGI1
Correct answer: Anti-AChR
Anti-acetylcholine receptor (AChR) antibodies are positive in ~85% of generalized myasthenia gravis cases and are the first-line test.
MD Central Nervous System Disorders 2
A 45-year-old man presents with sudden onset of thunderclap headache reaching maximal intensity within seconds.
CT head is negative.
What is the next best step?