Imaging characteristics of metastatic lesions to the cerebellopontine angle

OBJECTIVE: To describe characteristic features of metastatic lesion to the cerebellopontine angle (CPA) and internal auditory canal (IAC). STUDY DESIGN: Retrospective review. SETTING: Tertiary care medical center. PATIENTS: Patients with metastatic lesions to the CPA. INTERVENTION: Diagnostic. MAIN OUTCOME MEASUREMENTS: Clinical presentation and imaging characteristics on magnetic resonance imaging and computed tomography. RESULTS: A total of 25 cases were reviewed. The average patient age was 56 years, and almost all patients presented with palsy of the cranial VII and VIII nerves. There were 14 cases of metastases to the CPA, 16 cases to the IAC, 5 cases to the CPA and IAC, and 7 cases to the dura. There were several identifiable patterns of metastases to the CPA/IAC, including the flocculus (5), pia/arachnoid (12), dura (7), and choroid plexus (3). T1 magnetic resonance imaging was most commonly isointense to hypointense to brain, with enhancement on T1 imaging with contrast. Lesions tend to be eccentric to the IAC. T2 and fluid-attenuated inversion-recovery (FLAIR) imaging shows adjacent cerebellar and brainstem vasogenic edema. Characteristics that differentiate metastatic lesions from benign lesions of the CPA include vasogenic edema on T2 and FLAIR imaging and multiple central nervous system lesions and lesions that are eccentric to the IAC. CONCLUSION: Recognizing characteristic patterns of spread to the CPA and IAC can aid the clinician in the diagnosis of metastatic lesions to this area. Clinical history of rapidly progressive cranial nerve deficits, particularly facial paralysis in a patient with a history of malignancy, increases the level of suspicion. Imaging characteristics of metastatic lesions to the CPA include adjacent vasogenic edema observed on T2-weighted imaging and FLAIR, eccentric location to the IAC, and multiple lesions observed on head and neck imaging.