Transcallosal approach to tumors of the third ventricle. Surgical results and neuropsychological evaluation.

A series of 34 patients with tumours of the third ventricle were operated on by a transcallosal route. Basal extrinsic lesions compressing or invading the ventricle as well as tumours located in the pineal area were excluded from this review. Tumours were approached by a transforaminal entry in 16 cases (47%), by an interforniceal route in 11 (32%), by a subchoroidal entry in 4 (14%) and by a combined transforaminal and subchoroidal entry in 3 (9%). Four out of 34 patients were submitted to a second operation, through the same approach corridor: 2 for an incomplete removal of an intrinsic tumour and 2 for a late regrowth. Postoperative mortality rate accounted for 5.8% (2 patients). Major post operative complications were hemiparesis (4 patients) and diabetes insipidus (4 patients), that were transient in 3. Akinetic mutism like status was observed in only 1 patient. Postoperative psychic disturbances were noticed in 5 cases. Nine out of 21 patients (62%) with preoperative hydrocephalus required a permanent CSF shunt. Histology revealed that 21 tumours (62%) were intraaxial (4 pilocitic astrocytoma, 10 low grade glioma, 1 giant cell astrocytoma, 1 subependymoma, 4 ependymoma/ependymoblastoma, 1 neurocitoma) and 13 (38%) were extraaxial (8 colloid cyst, 2 craniopharingioma, 1 ectopic pituitary adenoma, 1 lymphocytic hypophysitis and 1 metastasis). Total excision of third ventricle tumours was achieved in all patients with extraaxial tumours and in 62% and 71% of intraaxial tumours with the first and second surgical procedure respectively. Ten out of 34 patients of this series were submitted to a complete neuropsychological evaluation at an interval of 2-9 years after surgery. Memory tests were pathological in 2. Disconnection signs were constantly absent. Control function were preserved. Transcallosal approach remains the best microsurgical method of third ventricle tumours treatment. This route provides the capability for a superior visualization of the entire cavity of the third ventricle through different corridors. Permanent neurological and neuropsychological deficits are not frequent. Epilepsy, that accounted for 28% in patients submitted to transcortical transventricular approach to third ventricle tumours, was never noticed in this series operated on through a transcallosal route.