Minimally invasive treatment for drug-resistant epilepsy
As many as 1 in 30 patients will experience a seizure in their lifetime, and a large number of patients will go on to have epilepsy. But it’s worth noting that many of these patients will be prescribed some sort of medicine to better control their symptoms. This won’t work for everybody. One anticonvulsant is not enough for many patients. But, according to pooled data, adding a second AED only gives you a 13% chance of seizure freedom. And a third AED? 1% of those patients will be seizure free. So what can we do for our patients who suffer from refractory seizures? Is surgery the only option?
In a prior episode featuring Torie Robinson on the surgical management of drug-resistant epilepsy, we also discussed the psychosocial impact of having such a stigmatizing diagnosis. But undertaking a major brain surgery is not an option for many people, and a large proportion of epileptics won’t want to undergo this type of invasive and risky procedure. So what are the other options for these patients? In this week’s episode, Dr. Myriam Abdennadher from the NIH joins me to discuss the types of minimally invasive procedures we can offer some of these patients.
Definition. The International League Against Epilepsy definition of Drug-Resistant Epilepsy is “failure of adequate trials of two tolerated and appropriately chosen and used AED schedules (whether as monotherapies or in combination) to achieve sustained seizure freedom.” Most epileptologists consider after 1-2 years of two failed antiepileptic therapy, the patient has a drug resistant epilepsy. Adding more than 2 meds rarely will achieve seizure freedom, and often carries greater risk of complications, such as toxic medication side effects (dizziness, rash, sedation) as well as a greater risk of Sudden Unexpected Death in Epilepsy Patients (SUDEP). According to one case-control study which adjusted for seizure frequency, patients who were prescribed 3 AEDs were 8 times more likely to experience SUDEP when compared to patients on only one drug. But not every severe case of epilepsy, or every patient with drug-resistant epilepsy, will be great candidates for brain surgery.
Dietary changes are helpful for some patients. This is worth discussing in greater detail at a later time. Briefly, several diets have been helpful, especially in childhood epilepsies:
- Ketogenic diet (most popular, probably most effective)
- Modified atkins diet
- Low glycemic index diet
One minimally invasive option, which we will discuss in more detail next week, is vagal nerve stimulation (VNS). VNS involves the surgical placement of electrodes in contact with the left vagus nerve, and it acts as a sort of pacemaker by delivering repetitive signals here. We don’t really know how this works, but it’s hypothesized to augment central nervous system gabaergic and glutamatergic transmission via peripheral nervous system stimulation. A more invasive option would be Responsive Neurostimulation (RNS). While VNS is more of a pacemaker, the RNS acts like a defibrillator—recognizing abnormal electrical rhythms of the brain, and delivering small impulses to abort them.
But this week’s episode features a discussion on stereotactic laser ablation (SLA), which is the minimally invasive version of surgical resection for abnormal brain tissue that may be epileptogenic. The procedure for SLA consists of putting an optic fiber stereotactically in the target. Then, the surgeon would induce thermal ablation of the area with live (real-time) MRI and temperature control mapping (below). Dr. Abdennadher goes into much greater detail for this type of procedure, but basically it is effective at treating inaccessible seizure foci for patients who are not great surgical candidates, or–no surprise here–don’t want to have brain surgery.
So there are a lot of unique techniques when it comes to minimally invasive procedures for drug-resistant epilepsy. VNS and RNS, as we’ll discuss next week, can achieve a high degree of seizure control with minimal risk. Stereotactic laser ablation can reach difficult to access seizure foci, deep within the brain, using an optical catheter. And if it fails, who is to say that it’s the last option for these patients? Some have undergone multiple types of surgical and non-surgical procedures for their refractory seizures. So keep an open mind about the minimally invasive neurosurgical options for epileptic patients.
Before we wrap up, Dr. Abdennadher had one last message she wanted to share with all our neurology community:
Now we know that have good surgical procedures and several minimally invasive procedures for our patient with refractory epilepsy. So, Please refer these patients early to comprehensive epilepsy centers for surgical evaluation. Because, if we achieve good epilepsy control, we save our patient many years of bad life quality.
I couldn’t agree more.
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- Kwan P, Arzimanoglou A, Berg AT, Brodie MJ, Allen Hauser W, Mathern G, Moshe SL, Perucca E, Wiebe S and French J. Definition of drug resistant epilepsy: consensus proposal by the ad hoc Task Force of the ILAE Commission on Therapeutic Strategies. Epilepsia. 2010;51:1069-77.
- Nilsson L, Farahmand BY, Persson PG, Thiblin I and Tomson T. Risk factors for sudden unexpected death in epilepsy: a case-control study. Lancet. 1999;353:888-93.
- Tomson T, Nashef L and Ryvlin P. Sudden unexpected death in epilepsy: current knowledge and future directions. The Lancet Neurology. 2008;7:1021-31.
- Willie JT, Laxpati NG, Drane DL, Gowda A, Appin C, Hao C, Brat DJ, Helmers SL, Saindane A, Nour SG and Gross RE. Real-time magnetic resonance-guided stereotactic laser amygdalohippocampotomy for mesial temporal lobe epilepsy. Neurosurgery. 2014;74:569-84; discussion 584-5.