A patient develops palatal myoclonus years after a brainstem stroke. MRI shows enlargement and T2 hyperintensity of one inferior olivary nucleus. Interruption of which tract caused this transsynaptic degeneration?

• A Medial longitudinal fasciculus
• B Central tegmental tract ✓
• C Lateral lemniscus
• D Superior cerebellar peduncle

Explanation

Hypertrophic olivary degeneration follows disruption of the Guillain-Mollaret triangle, whose limb from the red nucleus to the ipsilateral inferior olive is the central tegmental tract. Loss of this input causes vacuolar hypertrophy rather than atrophy of the olive, producing palatal myoclonus months to years later. The superior cerebellar peduncle forms the dentato-rubral limb but does not connect directly to the olive, so isolated damage there does not produce this picture.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.