A patient with a brainstem lesion shows contralateral hemiplegia and ipsilateral oculomotor nerve palsy. The lesion is most precisely located in the:

• A Anterior pons
• B Medullary pyramid
• C Crus cerebri (basis pedunculi) at the midbrain level ✓
• D Internal capsule posterior limb

Explanation

Weber syndrome (ipsilateral CN III palsy + contralateral hemiplegia) results from a midbrain lesion involving the crus cerebri (corticospinal fibers) and the emerging CN III fascicles. The corticospinal fibers at this level are in the basis pedunculi before they decussate at the pyramidal decussation in the medulla. Internal capsule lesions would not affect CN III.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.