When do we say seizures are refractory to medicines?
Assistant Professor of Neurology
New York-Presbyterian Hospital
Weill Cornell Medical Center
New York, NY 10065
Yesterday I saw a patient with medically refractory epilepsy in my office. As I took pains to explain to the family about refractory seizures, I realised that understanding the same can be difficult for a lay person. So in this post I shall talk about refractory seizures.
So what do I mean if I say a patient has medically refractory epilepsy or medically refractory seizure disorder? In simple words all I am saying is that the patient has a seizure disorder which has not shown an adequate response to anti-seizure medicines.
In most patients with epilepsy/ seizure disorder, adequate seizure control can be obtained by just one seizure medicine. By adequate control I mean no more seizures. No more seizures, the side-effects of the anti-seizure medication used are tolerable (if none that is the best): the patient is happy and I am happy. While good control of seizures can be obtained in the majority of patients, there are a few in whom the seizures are harder to control. You use one seizure medicine but the seizures still persist, you stop the first and use a second-still seizures, you try a third-same story. You start using 2 or more drugs together (at the same time) to try control the seizures. This is referred to as polytherapy or polypharmacy. You can imagine what happens next. The patient is on 3 and at times more drugs, more side-effects, more drug-drug interaction and at times still poor seizure control. The patient feels miserable and I am not happy too. Such a patient has medically intractable epilepsy, seizures are refractory to medications.
So what can be done for a patient who has medically refractory epilepsy? Can we offer them something to control their seizures. I am happy to say yes. Patients with medically refractory epilepsy should be ideally seen in specialized epilepsy centers (comprehensive epilepsy centers). These centers offer expertise: patients can be enrolled in trials of experimental drugs, other options like neurostimulation (vagus nerve stimulator) and finally epilepsy surgery can be explored (see my post on epilepsy surgery at http://braindiseases.info) .
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