Gamma Knife

[Bernard]

Does anyone here have any experience (or second hand stories) with Gamma Knife treatments for epilepsy?

[Bernard]

I received the following info via email and am sharing it with the author's permission:

Just some info on the Gamma knife. Our neurosurgeon and I discussed this a while back.

Gamma knife works best for lesions which can easily be identified on a scan - like a tumor. It destroys the bad tissue (or a specific area, like in mesial temporal sclerosis.)

The problem with the gamma kinfe, is that it cannot target the surrounding areas which know how to seizure, that is, the epileptic zone. Kinda like the yolk of an egg is the focus and the white of the egg is the zone. When you crack an egg into a pan, the egg white doesn't remain in an intact circle like the yolk - it spreads around the yolk in various ways, sometimes a section of the yolk is close to the edge, while other areas have more egg white from the edge to the yolk. Even if a clear structural lesion can be identified on MRI, the zone is invisible. In extratemporal epilepsy, grids have to be placed to no only identify the focus, but the surrounding zone. Once the grids are placed, the focus and zone are identified, then functional mapping can be done. Mapping tells us the precise brain function under each electrode. Motor and speech areas are not removed even if it is part of the focus or zone.

Actually, ressective surgery so far has been more effective than gamma knife surgery for epilepsy. When ressective surgery is performed, more brain tissue is removed than one imagines. Gamma knife destroys smaller areas of tissue, and it works best for tumors which can be seen easily on an MRI. Some centers are performing Gamma knife surgery for epilepsy, using functional MRI, pet and spect scans and not putting the patient through "grids". However, most epilepsy centers and not confident enough in gamma knife for epilepsy - there just isnt' enough "good outcome" data for epilepsy surgeons to persue this.