Transcallosal removal of lesions affecting the third ventricle: an anatomic and clinical study.

A series of 54 patients with lesions affecting the third ventricle with a wide range of pathology were operated on by the transcallosal approach. Hydrocephalus was present in 68.5% of all patients, and preoperative shunting was performed in 73.0% of them. Before the partial callosotomy, 16 patients were studied by the use of a cognitive, affective, and behavioral battery, which was repeated 10 and 100 days after the operation. No physiological consequences were ever observed after the partial commissurotomy. The postoperative callosal defect was verified by magnetic resonance imaging. Furthermore, 40 formalin-fixed brains were sectioned to study the variations of the anterior cerebral arteries. On the other hand, magnetic resonance imaging measurements of the corpus callosum in 40 normal subjects were performed to establish a classification system for the corpus callosal area. The results showed a wide variability of the cross-sectional area of the corpus callosum. The differences in the thickness of the truncus were responsible for this variability; the length of the corpus callosum was uniform. This may suggest that subjects with a large corpus callosum may have more interhemispheric connections with higher specialization of each hemisphere and that a smaller number of callosal connections may correlate with more ipsilateral pathways and more independent hemispheres. The results and the clinical as well as anatomical material indicate that the anterior transcallosal route is a safe and feasible alternative in the management of a wide spectrum of pathological lesions within the third ventricle and deserves preference over the transcortical technique.