Chapter 62. Nonacoustic Lesions of the Cerebellopontine Angle

Vestibular schwannomas (acoustic neuromas) account for 80% of all lesions of the cerebellopontine angle (CPA). This chapter discusses some of the other common neoplasms (meningiomas and epidermoid cysts) as well as uncommon tumors of the CPA that commonly present with injury to the cochlear–vestibular system. Each of these tumors has a similar clinical presentation; they are primarily differentiated by their imaging characteristics.

The CPA consists of a potential space filled with cerebrospinal fluid (CSF) in the posterior cranial fossa bounded by the temporal bone, the cerebellum, and the brainstem. The CPA is traversed by cranial nerves V–XI and most prominently the facial (CN VII) and vestibulocochlear (CN VIII) nerves. CPA tumors account for 10% of all intracranial tumors (Table 62–1). Nearly 90% of all CPA tumors include vestibular schwannomas (acoustic neuromas) and meningiomas. Other CPA lesions include congenital rest lesions (eg, epidermoid cysts, arachnoid cysts, and lipomas), schwannomas of other cranial nerves, intra-axial tumors, metastases, vascular lesions (eg, paragangliomas and hemangiomas), and lesions extending from the skull base (cholesterol granulomas and chordomas). CPA lesions become clinically symptomatic by causing compression of the neurovascular structures in and around the CPA. The classic description of these symptoms initially includes unilateral hearing loss, vertigo, altered facial sensation, facial pain that later progresses to nystagmus, facial palsy, vocal cord palsy, dysphagia, diplopia, respiratory compromise, and death (Table 62–2).

Essentials of Diagnosis

• Asymmetric (unilateral) sensorineural hearing loss, tinnitus, or both
• More likely than vestibular schwannomas to have facial or trigeminal nerve findings, or both
• Dural tail and calcification are distinctive on imaging.

General Considerations

Meningiomas are the second most common CPA tumors and account for 3–10% of neoplasms at this location. Compared with schwannomas, meningiomas are a more heterogeneous group of tumors with regard to pathology, anatomic location, and treatment outcome. Most of these tumors are benign and slow growing; 1% will become symptomatic. Meningiomas differ in pathogenesis, anatomic location, and imaging ...