A patient presents with ipsilateral tongue deviation, ipsilateral sternocleidomastoid and trapezius weakness, and no sensory loss. At which point in the posterior cranial fossa could a single lesion account for all three findings?

• A Foramen magnum area ✓
• B Jugular foramen
• C Hypoglossal canal
• D Internal auditory meatus

Explanation

CN XI (accessory) arises from the upper cervical spinal cord (C1-C5), ascends through the foramen magnum, exits via the jugular foramen (spinal root), while CN XII exits via the hypoglossal canal. A lesion at the foramen magnum (e.g., meningioma, Chiari) can affect the spinal root of CN XI and the emerging CN XII together. The jugular foramen syndrome (Vernet) includes CN IX, X, XI, and does not primarily affect CN XII. Collet-Sicard syndrome (jugular foramen + hypoglossal canal) involves CN IX-XII; but the foramen magnum location best explains CN XI + XII without CN IX/X involvement.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.