A 42-year-old woman has a focal lesion of the right red nucleus in the midbrain tegmentum. The expected clinical finding is:

• A Ipsilateral CN III palsy with contralateral hemiplegia (Weber syndrome)
• B Ipsilateral CN IV palsy with contralateral ataxia
• C Ipsilateral CN III palsy with contralateral cerebellar-type tremor and ataxia (Benedikt syndrome) ✓
• D Bilateral internuclear ophthalmoplegia

Explanation

Benedikt syndrome results from tegmental midbrain infarction involving the CN III fascicles and the red nucleus. The ipsilateral CN III palsy occurs because fascicles pass through this region en route to exit. Involvement of the red nucleus (receiving crossed cerebellar output from the dentate nucleus via the superior cerebellar peduncle) causes contralateral rubral tremor, choreoathetosis, and ataxia. Weber syndrome spares the red nucleus and involves the cerebral peduncle instead, giving contralateral hemiplegia.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.