[High resolution T2 weighted MRI sequence and diagnosis of neurinoma of the VIII].

OBJECT

To assess the value of high resolution fast spin echo T2 weighted (HR-FSE T2w) sequence for the diagnosis of acoustic neuroma. Two criteria for normality of the HR-FSE T2w examination are defined.

PATIENTS AND METHODS

114 patients underwent MR imaging at 1.5 T. The protocol included: axial images; 2 overlapped sequences focused on the internal auditory meatus (IAM), HR-FSE T2w acquisition (512 matrix, 3 mm sections with 1.5 mm overlapping); pre and postcontrast T1 weighted sequences focused on IAM. We defined two criteria for a normal HR-FSE T2w image: cerebellospinal fluid visible throughout the IAM, cochleo-vestibular and facial nerves visible in the IAM.

RESULTS

31 examinations were abnormal with HR-FSE T2w sequence, 25 lesions were found on postcontrast T1 weighted sequence (i.e. 6 false-positive results and none false-negative). The sensitivity, specificity and negative predictive value of this HR-FSE T2w sequence were 100%, 97% and 100% respectively.

CONCLUSION

the HR-FSE T2w sequence is the first-line method for detecting tumoral lesions of the IAM. If the 2 normality criteria are present on the HR-FSE T2w images, the T1w sequence with gadolinium injection is of no use; the injection of gadolinium remains necessary if only one of these criteria is lacking.