gms | German Medical Science

Objective: Epidermoid cysts (ECs) comprise 6%–7% of all lesions of the cerebellopontine angle (CPA) and often have an extremely complex growth pattern. Complete removal through a single approach is often not possible.

The aim of this study was to analyze the volumetric extent of resection of the ECs of the CPA depending on their preoperative volume and location.

Methods: A total of 51 ECs of the CPA were operated at the Department of Neurosurgery of the University of Tübingen between January 2004 and February 2018.

The preoperative and postoperative MRI sequences (T2 ciss sequence and diffusion sequence) required for volumetric analyzes were found in 30 cases. These sequences were transmitted to iplan 7 (brainlab®). The ECs were contoured on each slice in the T2-weighted images manually and analyzed with focus on their extent.

Results: The mean age of the patients was 39 ± 16.57 years. Among the patients, 11 were males and 19 were females. The mean preoperative cyst volume was 18.34 cm³ (min: 1.6 cm³; max: 49 cm³). Complete removal of the EC was achieved in 19 cases. A nearly complete removal, with a small hyperdensity in the diffusion sequence in only one slice (volumetry was not possible due to these circumstances, resulting in missing of the three dimensions), was achieved in 6 cases. A partial resection, with a mean remnant volume of 6.52 cm³, was performed in 5 cases. In all the cases with a partial resection, the EC comprised portions of the anterior or the middle cranial fossa before surgery.

Conclusion: ECs of the CPA can be classified based on their location. There exists a relationship between preoperative cyst location and the extent of resection.