A 40-year-old man was admitted to the neurology service for evaluation of persistent numbness over his left jaw and lower face. MRI reveals a schwannoma, which is compressing a cranial nerve as the nerve exits the skull. The cranial nerve involved in this case exits the skull through which of the following foramina?
(A) Foramen ovale
(B) Foramen rotundum
© Foramen spinosum
(D) Jugular foramen
(E) Superior orbital fissure
The correct answer is A.
The foramina of the trigeminal nerve divisions can be remembered with the mnemonic Standing Room Only (SRO) for the Superior orbital fissure, foramen Rotundum, and foramen Ovale, which transmit cranial nerves (CNs) V1, V2, and V3, respectively. This patient has a schwannoma of the mandibular division of the trigeminal nerve (CN V3) as the nerve exits the skull through the foramen ovale. Compression of V3 causes numbness over the ipsilateral jaw and lower face.
Answer B is incorrect. The maxillary division of the trigeminal nerve (CN V2) exits the skull through the foramen rotundum and compression would cause decreased sensation over the cheek and middle face.
Answer C is incorrect. No cranial nerves exit through the foramen spinosum. The middle meningeal artery exits through this opening.
Answer D is incorrect. The jugular foramen transmits the glossopharyngeal (CN IX), vagus (CN X), and the spinal accessory nerve (CN XI).
Answer E is incorrect. CN III, IV, VI, and VI exit the skull through the superior orbital fissure. Lesions of these nerves would lead to ipsilateral extraocular muscle paralysis and numbness of the ipsilateral forehead and upper face.