Head and Neck Imaging

Acoustic schwannoma

benign neoplasm arising from the nerve sheath of the vestibulocochlear nerve. It is the most common neoplasm of the internal auditory canal and cerebellopontine angle. The most typical symptom is unilateral progressive sensorineural hearing loss; about 20% present with sudden hearing loss. Very small acoustic tumours may differ in their symptomatology from larger ones, sometimes only producing subtle asymmetrical symptoms (such as fullness in the ear or tinnitus).

Detection of an acoustic schwannoma at its earliest stage is desirable, as the morbidity of surgical excision (facial nerve damage and complete hearing loss) is clearly linked to tumour size. Gadolinium-enhanced MRI has been shown to be the most sensitive method in the detection of even very small acoustic schwannomas, such as purely intracanalicular or intralabyrinthine tumours (Fig.1). T2-weighted high resolution gradient echo or fast spin-echo sequences may become an alternative to the currently used gadolinium-enhanced MR screening protocols for acoustic schwannoma. Also, see neurofibroma acoustic.

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Fig.1

Axial T1-weighted MR images through temporal bones in a patient with left-sided sensorineural deafness: strongly enhancing area in the left vestibulum (a, arrow); compare with the right vestibulum (b, arrowhead). Surgically proven intralabyrinthine schwannoma.
Acoustic schwannoma, Fig.1 (a)
Acoustic schwannoma, Fig.1 (b)