Epilepsy related to hypothalamic hamartomas: surgical management with special reference to gamma knife surgery

A large spectrum of surgical techniques can be proposed to young patients presenting with hypothalamic hamartomas (HH) associated with severe epilepsy. The aim of this report is to point on some clinical and anatomical parameters supposed to influence the choice of the surgical approach and to emphasize the specific role of radiosurgery.

We reviewed both our experience and the recent literature based on a Pubmed search. Lateral pterional, midline frontal through the lamina terminalis, transcallosal interforniceal approaches, endoscopic treatment through the foramen of Monro, disconnecting surgery, radiofrequency ablation, brachytherapy and gamma knife surgery (GKS) were all considered. Mortality, morbidity, and efficacy of each of these techniques were compared. Specific limits, difficulties, and constraints were taken into account. Our experience of radiosurgery is based on a prospective trial which enrolled 60 patients with HH and associated severe epilepsy between October 1999 and December 2005.

Several surgical techniques can lead to a real reversal of the epileptic encephalopathy. The main factors for the decision-making process are the age, the size of the lesion and its anatomical type (according to our original classification), the severity of the epilepsy, and the severity of the cognitive/psychiatric comorbidity. In our prospective trial (GKS), 27 patients have a follow-up superior to 3 years. Among those, 59.2% have an excellent result with a dramatic behavioral and cognitive improvement and are completely seizure-free (37%) or have only rare non-disabling seizures (22.2%). No permanent neurological complication has been observed so far; three patients have presented a transient poïkilothermia. GKS is clearly the safer approach for these difficult patients. Young patients with severe epilepsy and comorbidity must be operated on using a curative approach as early as possible. Very large type VI or mixed type with a large component above the floor of the third ventricle must be disconnected and then the upper remnant can be ideally treated by GKS (staged surgery). Type V (rarely epileptic) and IV are frequently operable by disconnection. Type I HH deeply embedded in the hypothalamus are operated on by GKS efficiently and safely. Type II HH can be operated on either endoscopically or transcallosally or by GKS depending on the parents' choice and severity of epilepsy. In small type III HH, GKS is a safer procedure, due to the very close relationship to the fornix and mammillary bodies. In very large type III HH, transcallosal interforniceal approach is proposed but with significant risks especially concerning short-term memory. When the lesion is sufficiently small, GKS is globally offering the patient a rate of seizure cessation comparable to microsurgery with, however, a much lower risk (no neurological deficit reported till now).

Our first results indicate that GKS is as effective as microsurgical resection and very much safer. GKS also allows avoiding the vascular risk related to radiofrequency lesioning or stimulation. The disadvantage of radiosurgery is its delayed action. Longer follow-up is mandatory for a reliable evaluation of the role of GKS. The early effect on subclinical discharges turns out to play a major role in the dramatic improvement of sleep quality, behavior, and developmental learning acceleration at school.