Focal epilepsy in children due to unilateral polymicrogyria: Decision making, surgical treatment and outcome

Objective: Malformations of cortical development are a frequent cause of drug resistant focal epilepsy in children. Unilateral polymicrogyria (upmg) represents a special late-organizational disorder of cortical development. Clinical course of epilepsy and epilepsy related mental retardation as well as the extent of motor handicap of the contralateral side may vary over a wide range which may influence decision making. We report a group of 12 children with upmg with respect to operative procedure, postoperative seizure outcome, mental situation and motor function of the paretic side.

Methods: From 1998–2010 a group of 12 children showed the characteristic pattern of upmg and were candidates for an operative procedure. To prove the existance of ipsilateral cortico-spinal projections, all children were examinated by transcranial magnet stimulation (tms). All but two underwent hemispherotomy. In one patient a temporo-parieto-occipital resection, in the other patient a subtotal hemispherectomy sparing the sensory motor cortex was done after invasive monitoring.

Results: All 12 male patients, preoperative severely mentally retarded expect for one normal-mildly retarded boy, improved after surgery. Postoperative 11 children had complete relief from seizures, while one had very rare seizures. The tms showed ipsilateral connections to the paretic hand in 9/12 children.

Conclusions: Children with focal epilepsy due to unilateral pmg are good candidates for surgical treatment. Beside severe epilepsy, the epilepsy-associated cognitive decline due to secondary bilateral synchrony, the extent of preoperative motor handicap and the existence of motor reorganization may be critical in the decision for the operation. While hemispherotomy is the most and effective procedure, in selected cases a multilobar resection to avoid functional deficit may be successful.