Epilepsy

One of the earliest observations made after treating tumours and arteriovenous malformations with the Gamma Knife in the 1970’s was that secondary focal epilepsy stopped. This has led to the empirical treatment of focal epilepsy by radiosurgery, especially epilepsy originating from the temporal lobe. The method is a non-invasive alternative to surgical treatment for epilepsy.

Amygdalohippocampectomy using the Gamma Knife with isocenters covering the region of the mesial temporallobe

In a series of patients with AVM treated at Karolinska by Gamma Knife it was observed that 52 out of 59 cases with epilepsy were cured of their fits even though the AVM was not always completely obliterated. This led to the concept that radiosurgery may modify epileptogenic activity and attempts were made to ablate the epileptic focus in other patients where the focus could be defined.

The largest experience is in mesial temporal sclerosis. Regis et al (1) performed amydalo-hippocampectomy with the Gamma Knife and after this 81% of patients were seizure free at 2 years or more follow up. Ablation of the whole area of amygdala and hippocampus requires a large radiation dose and risks a local radiation reaction. Regis has concentrated recently on lesioning the parahippocampal gyrus, with satisfactory results and reduced complications. The results will be published shortly.

Research using magnetoencephalography, functional MRI and PET to localize epileptic activity is likely to increase the proportion of patients found to have focal epilepsy. These imaging methods allow stereotactic targeting of foci and the role of the Gamma Knife is likely to become more important.

REFERENCES

1. Regis J, Bartolomel F, Rey M et al. Gamma knife surgery for mesial temporal lobe epilepsy. J Neurosurg 2000; 93 (suppl 3): 141-146.