Telo-velar approach to fourth-ventricle tumours: how I do it.

BACKGROUND: The "telo-velar" approach is an alternative to cerebellar splitting to gain access to the fourth ventricle through the so-called cerebello-medullary fissure (CMF).

METHOD: In this approach, the CMF is exposed and access to the ventricle is obtained by incising the tela chorioidea and inferior medullary velum. This approach enables the exploration of the entire ventricle cavity from the obex to the aqueduct.

CONCLUSIONS: The exposure of the fourth ventricle is satisfactory and the floor of the fourth ventricle can be visualised early and protected. The extent of resection and outcome are satisfactory in most patients, including those with large tumours or lesions attached to the lateral or superolateral recesses of the ventricle. The deep rostral tumour attachment is the main limitation of the telo-velar approach.

KEY POINTS: • Early exposure of the interface lesion-floor of the fourth ventricle favours a safer tumour dissection. • We feel that resection of tonsils is not necessary in the surgical setting. • The posterior arch of C1 should be removed only if the tonsils are below the level of the foramen magnum. • The improved access to the lateral recess of the ventricle makes the telo-velar approach particularly effective in lesions attached to cerebellar peduncles. • The wide dissection of the cerebello-medullary fissure and gentle tonsils retraction may prevent from the occurrence of cerebellar mutism or other major cerebellar dysfunctions. • Even the bilateral opening of the CMF does not result in cerebellar mutism if wide and cautious dissection, avoiding retraction and vascular injuries, is obtained. • The exposure of the fourth ventricle was satisfactory also in patients harbouring lesions attached to the lateral or even the superolateral recesses of the ventricle. • A deep rostral tumour attachment seems to be, at least in our experience, the main specific limitation of the telo-velar approach. • The risk of hydrocephalus can be reduced by opening of the fissure bilaterally, exposing the aqueduct, and by cisterna magna-fourth ventricle communication augmentation. • The EVD is taken in place for 48-72 h to prevent possible abrupt increase of the intracranial pressure and to favour wound closure.