Microsurgical anatomy of the white matter tracts in hemispherotomy

Hemispherotomy is a surgical procedure performed for refractory epileptic seizures due to wide hemispheric damage.

To describe the microanatomy of the white matter tracts transected in a hemispherotomy and the relationship of the surgical landmarks used during the intraventricular callosotomy.

The cortical and subcortical structures were examined in 32 hemispheres.

Incision of the temporal stem along the inferior limiting sulcus crosses the insulo-opercular fibers, uncinate, inferior occipitofrontal and middle longitudinal fasciculi, anterior commissure, and optic and auditory radiations. The incision along the superior limiting sulcus transects insulo-opercular fibers and the genu and posterior limb of internal capsule. The incision along the anterior limiting sulcus crosses the insulo-opercular fibers, anterior limb of the internal capsule, anterior commissure, and the anterior thalamic bundle. The disconnection of the posterior part of the corpus callosum may be incomplete if the point at which the last cortical branch of the anterior cerebral artery (ACA) turns upward and disappears from the view through the intraventricular exposure is used as the landmark for estimating the posterior extent of the callosotomy. This ACA branch turns upward before reaching the posterior edge of the splenium in 85% of hemispheres. The falx, followed to the posterior edge of the splenium, is a more reliable landmark for completing the posterior part of an intraventricular callosotomy.

The fiber tracts disconnected in hemispherotomy were reviewed. The falx is a more reliable guide than the ACA in completing the posterior part of the intraventricular callosotomy.