MRI screening for acoustic neuroma: a comparison of fast spin echo and contrast enhanced imaging in 1233 patients

Gadolinium enhanced MRI is the gold standard investigation for the detectio n of acoustic neuroma. Non-contrast MRI sequences have been suggested as an alternative for screening examinations. In order to determine the utility of fast spin echo imaging, both gadolinium enhanced T-1 weighted images and fast spin echo T-2 weighted images were acquired in 1233 consecutive patie nts referred for exclusion of acoustic neuroma. Two radiologists independen tly recorded their findings. Fast spin echo T-2 weighted images were evalua ted with respect to the visibility of nerves within the internal auditory c anals and allocated a confidence score for the presence or absence of acous tic neuroma. 33 acoustic neuromas were identified. Only 56% were confidentl y identified on fast spin echo T-2 weighted images alone; gadolinium enhanc ed T-1 weighted images were required to confirm the diagnosis in 44% of the cases, including 9 of the 10 intracanalicular tumours. However, when ident ification of two normal intracanalicular nerves is employed as the criterio n of normality, the single fast spin echo T-2 weighted sequence excluded ac oustic neuroma in 59% of this screened population. It is concluded that an imaging strategy intended to identify small intracanalicular acoustic neuro mas cannot rely on fast spill echo T-2 weighted imaging alone. Gadolinium e nhanced T-1 weighted imaging could be restricted to patients where fast spi n echo images do not exclude acoustic neuroma but this strategy requires co ntinuous supervision by an experienced radiologist. In most practices the s creening examination should continue to include a gadolinium enhanced seque nce in order to optimize the detection of small acoustic neuromas.