FALSE-POSITIVE MRI IN THE DIAGNOSIS OF SMALL INTRACANALICULAR VESTIBULAR SCHWANNOMAS

The current gold standard for diagnosing vestibular schwannomas is MRI with gadolinium-DTPA enhancement. This imaging modality is particular ly useful in the detection of small intracanalicular tumours which can be missed by CT scanning. We present a case where MRI with enhancemen t suggested the presence of a 4 mm intracanalicular vestibular schwann oma. Surgical exploration of the internal auditory canal via a retrosi gmoid approach, revealed no tumour, but inflammatory arachnoid matter around the vestibular nerve was found. A review of the audiological te st results uncovered some results which did not correlate with the int erpretation of the MRI scan. We would therefore caution against immedi ate surgical intervention in patients where the diagnosis of a small i ntracanalicular vestibular schwannoma is not totally supported by the audiological findings. In such cases rescanning with gadolinium enhanc ement after a suitable interval is recommended.