Surgical Technique

A number of techniques are employed for hemispherectomy, ranging from an anatomically complete operation in which the whole hemisphere is removed, preserving only the basal ganglia, to a hemispherotomy, in which the aim is to remove the smallest amount of brain tissue and still achieve complete hemispheric disconnection. The original operation, described by Krynauw in 1950, was, in effect, a hemi-decor-tication, usually described as an anatomically complete hemispherectomy.

There are three major steps involved in an anatomical hemispherectomy: ligation and division of the middle cerebral artery distal to the lenticulo-striate arteries; division of the remaining arterial supply and venous drainage of the hemisphere; and the removal of the hemisphere. This was abandoned in the 1970s because of the complication of late delayed bleeding (cerebral hemosiderosis) which occurred in up to a third of patients and was often fatal. The use of Adams' modification in which, amongst other features, the enormous cavity in contact with the sub-arachnoid space is converted into an extradural space led to a significant reduction of late hemosiderosis.

Rasmussen described a sub-total or functional hemispherectomy, in which blocks of cortex are left anteriorly and posteriorly but isolated functionally by callosal section. Hoffmann in Toronto has used a form of hemicorticectomy which only extends down to the white matter, in order to overcome the late risks, although these were less effective in the control of seizures.

In historical series of hemispherectomy, the overall results were good, with 70-80% of patients seizure free. The Palm desert experience, reported in 1993, gives 67.4% seizure free, with 21.1% improved and a failure rate of about 11.6%. The corresponding figures for multi-lobar resection are 45.2% seizure free, with a failure rate of 19.5% [17]. Other benefits include improved intellectual performance and behavior if the seizures are controlled.

Gradually, the extent of tissue resection in functional hemispherectomy has diminished so that the operation has become more and more of a disconnection. A new technique - hemi-spherotomy - has been reported, in which the major fiber tracts are divided with minimal removal of the pathological brain tissue [18]. The results are similar, at least in the short term, to those of hemispherectomy. The technique involves shorter operation times, much less operative trauma and less blood loss; these are all-important considerations when operating on infants.

A multi-center case study by Holthausen described 333 patients from 13 centers. The pathology and operative techniques were varied. Overall, 328 patients were available for follow-up and there were five pre-operative deaths (1.5%). Using a classification in which all the patients who fell within Engel group 1 were described as seizure free, there were 231 patients who fell into this group (70.4%). Detailed analysis suggested that surgical technique was important, with hemispherotomy and Adams techniques producing significantly better results than the others. Although pathology was not a significant factor, Holthausen notes that the various manifestations of cortical neuromigrational disorder did worse [19]. In a recent report, only 44% of children with

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