Telovelar approach to the fourth ventricle: operative findings and results in 16 cases.

BACKGROUND: The cerebellomedullary fissure as a corridor for exposure of the fourth ventricle without vermian splitting is enjoying increasing application as a technique for exposure, to avoid the complications related to vermian splitting. The purpose of this study is to describe the operative findings and the results in 16 fourth ventricular tumours removed via telovelar approach. The impact of the pathological nature of the lesion on the degree of tumour removal is also discussed.

METHODS: Telovelar approach to the fourth ventricle was used in 16 consecutive patients. The charts were reviewed retrospectively. The pathological changes in the tela choroidea and inferior medullary velum, degree of tumour removal, and the clinical outcome are described.

FINDINGS: The tela choroidea was thinned out and streched over the tumour surface in 10 cases (large tumours). In epidermoid and dermoid cysts (3 cases), the tela choroidea was amalgamated with the tumour capsule. The inferior medullary velum was infiltrated by the tumour and was not detected as a separate layer in 6 cases (3 cases vermian astrocytomas and 3 cases medulloblastomas). The inferior medullary velum was thinned out and stretched as a neural tissue sheet over the tumour surface in 10 cases (4 ependymomas, 2 meningiomas, 2 epidermoids, one dermoid and one choroid plexus papilloma). Total removal was achieved in 11 out of 16 patients (68.75%). Subtotal removal was achieved in the remaining patients (31.25%); three ependymomas, one medulloblastoma, and one anaplastic astrocytoma. Cerebellar mutism was not observed in any patient and there was no mortality.

INTERPRETATION: Despite the panoramic view provided by the telovelar approach, the pathological nature of the lesion and vital neural tissue infiltration are limiting factors for total tumour removal. Total removal of tumours focally attached to critical areas in the fourth ventricle should not be attempted at the expense of patient's morbidity and mortality. To achieve optimum outcome, near total excision is acceptable in cases where complete removal may endanger function or life.