Hemispherical Deafferentation

Abstract

An alternative technique for so-called functional hemispherectomy has been developed to be used for the classical indications of hemispherectomy or the various modifications of functional hemispherectomy. The technique entails a smaller trepanation, less operation time, and less blood loss, and it leaves more brain tissue in place as compared with other functional hemispherectomy techniques. It starts with either hippocampectomy alone or with hippocampectomy and anterior temporal lobectomy. After this, deafferentation of the white matter of the temporal, occipital, parietal, and frontal lobe, using either a transcortical transventricular approach along the outline of the lateral ventricle or a sylvian key hole approach, is performed. The technique includes a transventricular callosotomy, and it leaves in place only a small portion of the suprainsular cortex and the insular cortex. However, as one modification, removal of the insular cortex can easily be performed, if necessary, and, as a second modification, the entire transventricular deafferentation can be performed through a sylvian key hole. In this report, the technique is described and the surgical experience for the first 13 patients is outlined. The immediate seizure relief with an average follow-up of 12 months was similar to that for patients with functional hemispherectomy, but the follow-up period for these 13 patients is not long enough to allow definite conclusions concerning long-term control of seizures and long-term complications.

Hemispherotomy and Functional Hemispherectomy: Indications and Outcomes

“…The seizure outcome for hemispherectomy and hemispherotomy is good in patients with acquired lesions and in patients with congenital malformations of cortical development, with a seizure-free rate of 60–90% and significant improvement occurring in about 10–15% of patients. 10 , 13 , 19 However, seizure outcomes differ greatly according to etiology and surgical techniques. 19 , 20 Rasmussen encephalitis, porencephaly secondary to perinatal stroke, and SWS have a better prognosis than cortical malformations such as hemimegalencephaly and cortical dysplasia, which may be associated with some degree of contralateral involvement.…”

“…However, recently developed hemispherotomy concepts make the seizure outcome similar among the three procedures (anatomical hemispherectomy and lateral and vertical functional hemispherotomy). 10 , 13 , 19 Even if seizure-free outcome does not depend on the surgical procedure, hemi-spherotomy techniques are highly recommended when insular and subcortical abnormalities are present. 24 …”

“…In order to avoid the severe complications of anatomical hemispherectomy, technical variations involving hemispherotomy with less resection and more disconnection have been described, such as hemidecortication by Ignelzi and Bucy, 6 functional hemispherectomy by Rasmussen, 7 and functional hemispherotomy by Delalande et al 8 The principle of functional hemispherotomy is leaving the live, vascularized brain, which is functionally disconnected from the contralateral healthy brain, intact. Hemispherotomy techniques were introduced in the 1990s by Delalande et al, 8 Villemure and Daniel, 9 and Schramm et al, 10 , 11 each with their own solution to achieving the disconnections required to attain complete functional disconnection of the hemisphere. Cook et al 12 described a modified lateral hemispherotomy, which involves sacrifice of the middle cerebral artery with removal of a central block of opercular tissue.…”

Fifty Consecutive Hemispherectomies

“…Aside from a single additional anatomic procedure performed for a revision hemispherectomy, all subsequent hemispherectomies, including 3 revision hemispherectomies, were done with the MLH technique. This technique was initially described by Cook et al in 2004 18 and is derivative of the peri-insular hemispherotomy techniques described by Schramm 19, 20 and Villemeure 21 in the 1990s. The features that distinguish this technique from peri-insular hemispherotomy techniques are: a) sacrifice of the middle cerebral artery (MCA) to facilitate hemostasis, thus limiting blood loss, b) resection of a central opercular block of tissue to provide generous exposure of the ventricular system and removal of the insula with portions of the basal ganglia and thalamus, and c) resection of the anterior temporal lobe.…”

Electrophysiological Sequelae of Hemispherotomy in Ipsilateral Human Cortex

“…This procedure has evolved from functional hemispherectomies (Rasmussen, 1983; Villemure and Rasmussen, 1993; Villemure et al, 2003) to functional hemispherotomies (Schramm et al, 1995; Villemure and Mascott, 1995; Carson et al, 1996; Kestle et al, 2000; Daniel et al, 2001; Limbrick et al, 2009). The hemispherotomy is traditionally reserved for medically-refractory epilepsy due to diffuse hemispheric disease and is thought to be effective because it prevents seizures from spreading to the contralateral hemisphere (Villemure and Rasmussen, 1993; Freeman et al, 1996; Daniel et al, 2001; Limbrick et al, 2009; Thomas et al, 2012).…”