MRI of acoustic schwannoma: a retrospective study of 89 tumours.

Magnetic resonance imaging (MRI) is now considered the diagnostic study of choice for evaluation of patients with suspected acoustic schwannoma. This retrospective study of 118 MR examinations presents an analysis of the MR findings of 89 acoustic tumours in 86 patients. The method of examination included precontrast and gadolinium(Gd)-enhanced MRI in 72 and plain MRI in 14 patients. The common MR-appearances of acoustic schwannomas were: on T1-weighted images (WI) isointense (36%) or slightly hypointense (64%) relative to the brainstem; intense and homogeneous contrast enhancement in 62%; the shape of the tumour was round or oval in 71%; the tumour was centred at/or located in the internal auditory canal (IAC) in 80%. The small acoustic schwannomas were mostly round or oval in shape and showed homogeneous signal intensity (SI) both before and after Gd. The larger acoustic tumours were more heterogeneous in morphology and SI. The significance of these and other signs, early diagnosis and differential diagnosis are discussed.