C. Ninth nerve schwannoma
A schwannoma is a benign and slow-growing tumor of Schwann cells of peripheral nerves. The most common schwannomas arise from the eighth cranial nerve, which can abut the brainstem and extend through the acoustic canal. However, schwannomas can arise along any peripheral nerve or the spinal cord; in this case, the tumor arises from the ninth nerve. Radiographically, schwannomas typically enhance brightly. They can have cystic components but are typically well circumscribed.
The differential diagnosis can include a meningioma, which is often difficult to distinguish from a schwannoma. However, meningiomas often have a broad dural-based attachment, whereas a schwannoma often has a rounder appearance and is independent of the dura.
A brain metastasis typically occurs within the brain parenchyma (rather than along a peripheral nerve) at the gray-white junction, and is usually rounded in appearance with heterogeneous enhancement. A glioblastoma multiforme is also typically a parenchymal lesion, with areas of necrosis and heterogeneous enhancement, rather than a peripheral lesion with relatively uniform enhancement.
Finally, this patient’s lesion arises in the jugular foramen, not the acoustic canal or along the eighth cranial nerve, thus distinguishing it from an eighth nerve schwannoma.
The patient was successfully treated with stereotactic radiosurgery.