CEREBELLOPONTINE ANGLE LESIONS - CT AND MR IMAGING EVALUATION.

Corresponding Author:
Dr. Sushant Agarwal,
Registrar,
Department of Radiology,
Gauhati Medical College & Hospital,
Guwahati-781032, Assam.
E-mail: sushantgmc@rediffmail.com

ABSTRACT

BACKGROUND

CPA lesions are clinically nonspecific and the presenting symptoms are not related to the nature of the lesion itself, but to the nerves or cerebral structure involved with the lesions. Therefore, preoperative diagnosis of a CPA region tumoural lesion is based on imaging.

Aim of the study was to determine various CT and MR imaging features of different CPA lesions and provide accurate possible preoperative diagnosis. To propose a concise algorithm to facilitate diagnosis and to correlate histopathologically post-operatively.

Materials and Methods

Retrospective observational study was carried out during a period from April, 2012 to March, 2015 on 62 selected patients referred from various departments with clinical suspicion, and after CT & MRI both revealed cerebellopontine angle lesions. Lesions were retrospectively analysed according to its relative CT attenuation, MR signal intensity with morphologic appearance on T1- and T2-weighted images and contrast enhancement patterns along with diffusion and spectroscopic features.

RESULTS

Of the total 62 cases, 40 patients had undergone operative treatment and rest of 22 cases were treated conservatively and radiotherapy. Histopathological findings are correlated in 40 patients. Majority 43.5% patients were in age between 41-50 yrs. Females predominated with 56.4% cases. Most common CPA lesion encountered was acoustic schwannoma (67.7% cases) followed by meningioma, arachnoid cyst and epidermoid. Most common presenting symptom was hearing loss (77.4%) followed by tinnitus (59.6%). Most CPA masses were hypodense on unenhanced scans (64.5%). Majority of acoustic schwannoma showed expansion of IAC (85.7%). Hydrocephalus and calcification seen mainly in acoustic schwannoma among all CPA masses. On contrast enhanced CT and MRI, majority CPA showed heterogenous enhancement. Dural tail sign seen in 5 out of 6 cases of meningioma. On MRS of CPA with large extracanalicular component, acoustic schwannoma showed MI peak (3.55 ppm) and meningioma showed alanine peak (1.47 ppm).

Conclusion

Both CT and MRI can depict the characteristic imaging features, allow a systematic approach to preoperative diagnosis in majority of cases. Advanced MR imaging techniques such as diffusion weighted imaging as well as spectroscopy help to differentiate variety of lesions.

Keywords

Acoustic schwannoma, Magnetic resonance imaging, Cerebellopontine angle.