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Top of the Basilar Syndrome — SCE Neurology MCQ

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HardCerebrovascular DiseaseTop of the Basilar SyndromeSCE Neurology

A 58-year-old man presents with sudden onset of oscillopsia and severe gait unsteadiness. Examination shows bilateral horizontal gaze-evoked nystagmus, downbeat nystagmus, and bilateral limb dysmetria. MRI brain shows bilateral cerebellar infarcts in the SCA territory. He also has a left Horner syndrome. What vascular syndrome is most likely?

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Correct answer: D — Top of the basilar syndrome

Top of the basilar syndrome results from occlusion of the rostral basilar artery, causing infarction in the midbrain, thalamus, and superior cerebellar territory bilaterally. Features include visual disturbances (hemianopia, cortical blindness), oculomotor abnormalities (vertical gaze palsy, convergence-retraction nystagmus, skew deviation), somnolence, behavioural changes, and bilateral cerebellar signs. The Horner syndrome results from midbrain sympathetic pathway involvement. A: Lateral medullary syndrome is PICA territory. C: AICA territory involves lateral pons and anterior cerebellum. D: Weber syndrome is ventral midbrain only. E: Medial medullary syndrome involves CN XII and corticospinal tract.

Reference: RCP National Clinical Guideline for Stroke (2023); Caplan Top of the Basilar Review