PANRE Neurology 3 — Questions and Answers
Question 1: A 45-year-old with HIV presents with focal seizures and a ring-enhancing lesion on MRI. The most likely diagnosis is:
- Primary CNS lymphoma
- Toxoplasma encephalitis (Correct answer)
- Progressive multifocal leukoencephalopathy
- Cryptococcal meningitis
Correct answer: Toxoplasma encephalitis
In HIV-positive patients, a ring-enhancing brain lesion most commonly represents Toxoplasma gondii encephalitis, especially when CD4 count is below 100 cells/µL.
Question 2: Which feature best differentiates migraine with aura from a TIA?
- Duration of symptoms
- Age of the patient
- Positive phenomena that march across the visual field (Correct answer)
- Presence of headache
Correct answer: Positive phenomena that march across the visual field
Migraine aura features positive phenomena (e.g., scintillating scotoma that spreads) and evolves slowly over minutes, while TIA causes negative, abrupt deficits.
Question 3: A patient with myasthenia gravis undergoes elective surgery. Which medication should be avoided perioperatively due to risk of cholinergic crisis if combined with pyridostigmine?
- Succinylcholine (Correct answer)
- Propofol
- Fentanyl
- Ondansetron
Correct answer: Succinylcholine
Succinylcholine is a depolarizing neuromuscular blocker metabolized by acetylcholinesterase; pyridostigmine inhibits this enzyme, leading to prolonged paralysis or crisis.
Question 4: A 30-year-old presents with bilateral leg weakness, ascending numbness, and loss of deep tendon reflexes following a GI infection 2 weeks ago. CSF shows elevated protein with normal cell count. Diagnosis?
- Multiple sclerosis
- Guillain-Barré syndrome (Correct answer)
- Transverse myelitis
- Botulism
Correct answer: Guillain-Barré syndrome
Guillain-Barré syndrome is a post-infectious ascending demyelinating polyneuropathy characterized by albuminocytologic dissociation (high protein, normal cells) in the CSF.
Question 5: Which antiepileptic drug is contraindicated in pregnancy due to highest risk of neural tube defects?
- Lamotrigine
- Levetiracetam
- Valproate (Correct answer)
- Oxcarbazepine
Correct answer: Valproate
Valproate inhibits folate metabolism and is associated with a 1–2% risk of neural tube defects and multiple other congenital abnormalities, making it contraindicated in pregnancy when possible.
Question 6: A patient has diplopia that worsens with upward gaze and a 'down and out' pupil-involving third nerve palsy. The most urgent concern is:
- Cavernous sinus thrombosis
- Posterior communicating artery aneurysm (Correct answer)
- Wernicke encephalopathy
- Diabetic microvascular infarction
Correct answer: Posterior communicating artery aneurysm
A pupil-involving CN III palsy is a neurosurgical emergency caused by compression of the third nerve — most commonly by a posterior communicating artery aneurysm.
Question 7: Which dementia is most associated with fluctuating cognition, visual hallucinations, and parkinsonism?
- Alzheimer disease
- Frontotemporal dementia
- Vascular dementia
- Lewy body dementia (Correct answer)
Correct answer: Lewy body dementia
Dementia with Lewy bodies presents with fluctuating cognition, well-formed visual hallucinations, and parkinsonism and is associated with sensitivity to antipsychotics.
PANRE Neurology 3
A 45-year-old with HIV presents with focal seizures and a ring-enhancing lesion on MRI.
The most likely diagnosis is: