SPEX Exam Neurology 6

Question 1

A 58-year-old man presents with progressive gait ataxia, autonomic dysfunction, and parkinsonism that is poorly responsive to levodopa. MRI shows atrophy of the pons, cerebellum, and middle cerebellar peduncles with a 'hot cross bun' sign. Which pathological hallmark distinguishes this condition from Parkinson's disease?

Accepted Answer

Glial cytoplasmic inclusions containing alpha-synuclein in oligodendrocytes

Answer

Multiple system atrophy (MSA) is characterized by glial cytoplasmic inclusions (GCIs) containing misfolded alpha-synuclein within oligodendrocytes — not neurons. This distinguishes it from Parkinson's disease, where alpha-synuclein aggregates form Lewy bodies within neurons. The 'hot cross bun' sign on MRI reflects cruciform T2 hyperintensity from selective pontine fiber degeneration.

Question 2

A 34-year-old woman with relapsing-remitting MS is started on natalizumab. After 24 months of therapy, JC virus antibody index rises to 3.2. She then develops rapidly progressive cognitive decline and focal deficits. CSF PCR is positive for JC virus at 450 copies/mL. What paradoxical worsening phenomenon must be anticipated when natalizumab is discontinued?

Accepted Answer

Immune reconstitution inflammatory syndrome (IRIS)

Answer

When natalizumab is stopped in the setting of PML, reentry of sequestered lymphocytes into the CNS triggers immune reconstitution inflammatory syndrome (IRIS). This causes an inflammatory flare around PML lesions that can be more acutely devastating than the underlying PML itself. Clinicians must balance accelerating natalizumab washout (plasmapheresis) against the severity of IRIS, sometimes requiring corticosteroids to blunt the inflammatory surge.

Question 3

A 67-year-old man presents with fluctuating cognition, visual hallucinations of small animals, REM sleep behavior disorder, and mild parkinsonism. His Mini-Mental State Examination score varies by 8 points between morning and afternoon assessments. Which pharmacological agent is MOST likely to cause life-threatening neuroleptic sensitivity in this patient?

Accepted Answer

Haloperidol

Answer

Dementia with Lewy bodies (DLB) carries a well-established severe neuroleptic sensitivity reaction to typical antipsychotics such as haloperidol, with up to 50% of patients experiencing acute deterioration, profound extrapyramidal rigidity, reduced consciousness, and death. While atypicals like quetiapine carry lower risk and are sometimes used cautiously, typical antipsychotics are contraindicated. Rivastigmine (a cholinesterase inhibitor) is actually a recommended first-line treatment for DLB-related hallucinations.

Question 4

A 45-year-old woman presents with subacute ascending weakness over 3 weeks, areflexia, autonomic instability, and CSF showing albuminocytologic dissociation. Nerve conduction studies reveal prolonged distal latencies, conduction block, and markedly slowed velocities in motor nerves. Anti-ganglioside antibody panel shows strong positivity for anti-GQ1b IgG. Which variant of Guillain-Barré syndrome does this antibody profile MOST specifically indicate?

Accepted Answer

Miller Fisher syndrome / Bickerstaff brainstem encephalitis overlap

Answer

Anti-GQ1b IgG antibodies are highly specific (>85%) for Miller Fisher syndrome (MFS), characterized by the triad of ophthalmoplegia, ataxia, and areflexia, and its brainstem-predominant overlap, Bickerstaff brainstem encephalitis. GQ1b ganglioside is abundantly expressed at paranodal myelin of oculomotor nerves and muscle spindles. AMAN is associated with anti-GM1/GD1a antibodies, while AIDP typically lacks specific anti-ganglioside antibodies.

Question 5

A 72-year-old man with a history of hypertension develops sudden onset of ipsilateral Horner syndrome, contralateral loss of pain and temperature below the neck, ipsilateral limb ataxia, dysphagia, and hoarseness, with intact motor strength and position sense. Which artery occlusion is responsible, and what is the eponymous name of this syndrome?

Accepted Answer

Posterior inferior cerebellar artery (PICA); Wallenberg syndrome

Answer

Wallenberg syndrome (lateral medullary syndrome) results from occlusion of the posterior inferior cerebellar artery (PICA) or the vertebral artery. It produces the characteristic crossed sensory pattern: ipsilateral face and contralateral body loss of pain/temperature (due to trigeminal nucleus and spinothalamic tract involvement respectively), ipsilateral Horner syndrome (descending sympathetics), ipsilateral cerebellar signs (inferior cerebellar peduncle), and bulbar symptoms (nucleus ambiguus). Motor strength and dorsal column sensation are preserved.

SPEX Exam Practice Test

SPEX Exam Practice Test

SPEX Exam Neurology 6