Surgical Strategy for Hemispherotomy

Abstract

Hemispherotomy is a radical treatment for drug-resistant epilepsy that targets developmental, acquired, and progressive diseases with widespread epileptogenic regions in one cerebral hemisphere. Currently, two main approaches are utilized after repeated improvements: lateral and vertical approaches. With the lateral approach, the surgical field is wide, and the approach to the lateral ventricle is relatively easy. On the other hand, the vertical approach has the advantage of reducing intraoperative bleeding and operating time as the resection line of the radial fiber is short, and understanding the three-dimensional anatomy is relatively easy. The lateral approach is generally used for atrophic lesions, whereas the vertical approach is for hypertrophic lesions. Hemispherotomy is expected to not only suppress epileptic seizures but also improve psychomotor development by protecting the unaffected cerebral hemisphere. However, this method is one of the most invasive surgeries in epilepsy surgery, and it is important to fully consider its indications. Furthermore, understanding the neural fiber pathway is important for actual surgery.

Keywords: epilepsy surgery; functional hemispherectomy; hemispherotomy; lateral approach; vertical approach.

Fig. 1

Schematic illustration of incision lines for the lateral (A) and vertical (B) approaches. Both approaches disconnect neural fibers from the contralateral cerebral hemisphere and ipsilateral basal ganglia/thalamus. The orange and green lines indicate assumed incision line. Circled numbers indicate steps.

Fig. 2

Intraoperative findings of the lateral approach. (A) Lateral surface of the left hemisphere. The black thread indicates an assumed disconnection line. The dotted line indicates the Sylvian fissure. (B) The hippocampal head (arrow) and inferior choroidal point (arrowhead) after opening the inferior horn of the lateral ventricle. (C) The foramen of Monro (arrowhead) and septal veins. (D) Disconnection of genu of the corpus callosum. The pericallosal artery was observed in the pericallosal cistern (arrowhead). The Liliequist membrane was observed beneath the anterior end of the corpus callosum (arrow). (E) Splenial lesion of the corpus callosum. Deep veins were observed after resection (arrowhead). (F) Final view of hemispherotomy with the lateral approach. The disconnection line almost overlaps with the assumed line.

Fig. 3

Intraoperative findings of the vertical approach. (A) The cavum vergae at the body of the corpus callosum (asterisk). (B) Approach into the lateral ventricle. The cingulate gyrus was partially excised. (C) The foramen of Monro (arrowhead). (D) The groove between the thalamus and caudate nucleus (arrow). (E) Choroid plexus at the lateral trigone (asterisk). (F) Disconnection of the horizontal fibers and the uncinate fasciculus. The brain parenchyma from the inferior choroidal point to the anteriormost point of the foramen of Monro was resected (dotted line).