Epilepsy surgery: just what is it?

Let us divert our attention for a few minutes to the topic of epilepsy surgery. Usually when one talks about epilepsy and its treatment, one thinks about medications. You are right, most of the patients with epilepsy shall have their seizures controlled by anti-epileptic drugs. However there are a few patients who have what we call medically refractory epilepsy, that is they have seizures which are refractory to anti-epileptic drugs (even if you use multiple drugs their seizures remain uncontrolled). Usually these are the patients whom we consider epilepsy surgery on.

So what is epilepsy surgery and what does it involve. In simple terms, we first try to map the seizures coming from the brain. By mapping I mean, we try to determine where exactly in the brain the seizures originate from (that is the seizure focus). Once we determine the seizure focus and are reasonably sure that all the seizures come from that focus only, then we open up the skull and the neurosurgeon resects that focus out ( kind of chopping off that part of the brain from which the seizures arise, once you remove the focus, the patient ideally should become seizure free and may be even able to come off his seizure medications).

While this procedure sounds good, it is way more complicated than what I explained above. First off all to meet the criteria for epilepsy surgery, a patient  should meet some criteria. What are these? Well first and foremost, we should be able to identify the seizure focus and be reasonably sure that all the seizures come from that very focus only. How do we do this you may ask. Well usually the patient is admitted for video-EEG study. We hook the patient to the EEG monitor and record the seizures. From the EEG we are able to localize the seizure focus. At times though the seizure focus cannot be identified for sure from the surface. In that case we do what is called intracranial monitoring. It is similar to the EEG except here we open up the skull and place the recording electrodes right on the surface of the brain itself.

Once we have localized the seizure focus, we have to make sure of a couple of things. One does that part of the brain serve any useful function? We are mostly worried about memory and speech issues. Secondly if it does house some memory or speech function, would it lead to any deficits if we take that part of the brain out. You do not want the patient to wake up from the surgery and not able to talk or have problems with memory. We test for this by a special test called the WADA test. This test helps us in determining the memory and speech localization in the brain.

Your doctor may also order additional tests again to aid in localizing the seizure focus. Some of these tests include special scans like the PET (positron emission tomography) and SPECT (single photon emission computed tomograpy) scans.

I hope this brief overview of what epilepsy surgery involves shall be helpful to some of you, we can go into more details if any of you requests it.

Nitin Sethi, MD