Epilepsy Surgery

temporal lobe. The authors then routinely perform EcoG, though not all surgeons subscribe to this.

A vertical cortical incision is made in the middle temporal gyrus at the posterior limit of the resection, staying anterior to the vein of Labbe and deepened down into the temporal horn of the lateral ventricle. In the next stage, the lateral neocortex (temporal operculum) is dissected sub-pially off the insula, maintaining the integrity of the arachnoid to protect the middle cerebral vessels. The dissection is then continued anteriorly down onto the floor of the middle fossa, following the curve of the sphenoid wing. Starting posteriorly, from the opening into the temporal horn, the white matter of the stem of the temporal lobe is progressively divided along the roof of the temporal horn, working anteriorly through the amygdala until the pia arachnoid of the pole of the temporal lobe is reached at the edge of the sphenoid wing. The previous incision in the middle temporal gyrus is then extended inferi-orly towards the floor of the middle fossa, cutting through the remainder of the middle and inferior temporal gyri. The dissection is continued medially until the hippocampus is reached. This is the most difficult stage of the procedure, due to the proximity of the posterior cerebral vessels and third and fourth cranial nerves at the tentorial edge. The choroid plexus is retracted medially to expose the choroid fissure and fimbria. This can be divided either with a small sucker or the CUSA. The dissection then proceeds anteriorly along the tentorial edge, coagulating and dividing the hippocampal branches of the posterior cerebral artery. The specimen can then be removed and a post-resection ECoG performed.

It is also possible to carry out a restricted removal of the mesial temporal structures, described as selective amygdalo-hippocampec-tomy, using a number of techniques, including either the trans-sylvian technique described by Yasargil or the transcortical approach originally described by Niemeyer [14]. The trans-sylvian approach is a technically demanding procedure, with a potential risk of vascular and cranial nerve damage, and should be reserved for those individuals in whom the seizure focus is clearly limited to the mesial temporal lobe structures. It is possible, but not clearly proven in the literature, that there could be fewer cognitive changes, especially in the dominant hemisphere

Direct operative mortality following temporal lobe resection is rare and is 0.5% in the authors' series. In the latest review, it is less than 1%, with some centers reporting no deaths in over 500 consecutive operations. Late mortality is a different matter. In Falconer's material, 19% of patients suffered late deaths, half from seizures. In the authors' own material, there were 17 deaths in 305 patients (5.6%), of which six were sudden and unexpected (SUDEP) and the remainder were related to epilepsy. A summary of physical complications from temporal lobec-tomy in published series is shown in Table 34.4.

Early studies showed that recent memory was a material-specific function, mediated by the temporal lobes, and that bilateral medial temporal resections would produce global amnesia [15]. In general, the post-operative changes in intellectual function depend upon the pre-operative state and the pathology. It was shown by Powell that those patients who were intellectually less able suffered less as a consequence of temporal lobe resection and, in general, these were patients with mesial temporal sclerosis who had undergone early brain reorganization

[15]. It was hoped that selective amygdalo-hippocampectomy would produce better cognitive results but, with the exception of the study by the Oxford group, this has not been proven

The overall seizure outcome for temporal lobe resections was quoted at the 2nd Palm Desert symposium as 68% seizure free, 24% improved and 9% not improved, using the Engel outcome scale [17]. The ILAE survey has similar figures - 57% seizure free, 27% improved and 10% not improved. The seizure outcome from temporal lobe surgery depends upon the type of resection and the pathology

Table 34.4. Complications from temporal lobe resections.


1975(%) 1987(%) 1993 (%)

Transient hemiparesis

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