Neuroradiological Aspects of Non Acoustic Tumours of the Cerebellopontine Angle

Abstract

We present a series of 17 non acoustic tumours of the cerebellopontine angle. They include ten meningiomas, five epidermoid cysts, one cavernous haemangioma and one cholesterinic cyst. In all cases histological verification was obtained at surgery. Evaluating the results of both CT and MRI studies, an accurate pre-operative diagnosis could be made in most cases. Meningiomas usually present as lesions with a semilunar shape, eccentric to the IAC, with smooth margins. The meningeal sign is usually observed while calcifications may he absent. On CT scan, the lesions were hypodense before contrast administration with a homogeneous marked enhancement after i.v. contrast administration. On MRI, on T1 WI the lesions were isointense and hyperintense on T2 WI. All cases markedly enhanced following gadolinium administration. Epidermoid cysts on CT were cystic hypodense lesions with a typical peripheral rim of enhancement. On MRI, they were hypointense on T1 WI and hyperintense on T2 WI. The typical peripheral rim of enhancement after GD-DTPA administration was also observed. Cholesterinic cyst was a well defined cystic lesion involving the petrous apex on CT. On MRI the typical increasing signal on both T1 and T2 WI was observed. In contrast to other lesions that require extensive surgery, the treatment of cholesterinic cyst may consist in simple drainage. Cavernous haemangiomas is a very rare lesion arising in the region of the geniculate ganglion of the facial nerve and may spread medially to involve the CPA. On CT, a stippled pattern of calcifications and contrast enhancement is observed. On MRI, the lesion is bright on T1 and T2 WI with gadolinium enhancement. The entire brain must be explored because other cavernous haemangiomas may also coexist.