Intracranial Neoplasms: The Daily PANCE Blueprint

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Intracranial Neoplasms: The Daily PANCE Blueprint

A 58-year-old man presents to the clinic with a 6-month history of progressive hearing loss in his left ear, intermittent episodes of dizziness, and a persistent ringing sensation. He also mentions some difficulty with balance and occasional numbness on the left side of his face. On examination, the Weber test lateralizes to the right ear, and the Rinne test shows air conduction greater than bone conduction bilaterally. Neurological examination reveals decreased corneal reflex and mild weakness of the muscles of mastication on the left side. An MRI of the brain shows a well-circumscribed mass at the left cerebellopontine angle. Which cranial nerve is most likely affected by this mass?

A. Facial nerve (CN VII)
B. Trigeminal nerve (CN V)
C. Vestibulocochlear nerve (CN VIII)
D. Glossopharyngeal nerve (CN IX)
E. Hypoglossal nerve (CN XII)

Answer and topic summary

The answer is Vestibulocochlear nerve (CN VIII)

The patient presents with unilateral sensorineural hearing loss (Weber test lateralizes to the right ear), tinnitus (ringing sensation), dizziness, balance difficulties, and facial numbness. These symptoms are classic for a schwannoma affecting the vestibulocochlear nerve (CN VIII). Schwannomas are benign tumors arising from Schwann cells, and CN VIII is the most commonly affected cranial nerve. The mass at the cerebellopontine angle on MRI further supports this diagnosis, as vestibular schwannomas typically occur in this location. The decreased corneal reflex and weakness of mastication muscles suggest involvement of the adjacent trigeminal nerve (CN V) due to the mass effect of the tumor, but these are secondary findings. The primary cranial nerve affected is CN VIII.

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Covered under ⇒ PANCE Blueprint Neurology ⇒ Neoplasms (Intracranial - benign and malignant)

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