Anterior thalamic stimulation for intractable epilepsy

Abstract

As per W.H.O. 50 million patients are suffering from epilepsy and out of them 80% are in developing countries. In India 1% of population suffer from epilepsy. 30% of these patients become refractory to medication and would require either surgery or deep brain stimulation. Deep brain stimulation is an established therapy for Parkinson disease, essential tremor and certain form of Dystonia. Recently it has been used in intractable epilepsy with good outcome in a SANTE clinical trial. The electrical stimulation of anterior thalamus can significantly reduce the number of seizures and can improve the quality of life. Based on both animal studies and clinical trials, we subjected six patients to anterior thalamic stimulation for medically refractory epilepsy. All six selected patients were not suitable for epilepsy surgery. The age ranged from 20 years to 53 years. Bilateral anterior thalamic stimulation was done in all cases using ZD stereotactic frame under general anaesthesia. The target was calculated using fused images of CT Scan and MRI. The placement of electrodes was confirmed by microelectrode recording (thalamic burst) and intra-operative driving response obtained by scalp EEG. The post-operative CT scan was done to confirm the position of electrodes.In three patients Medtronic DBS system (Activa PC) was used while other three patients have St Jute device (Libra) device. Anticonvulsant medications were kept unchanged. The programming was started after one week using electro encephalography. The reduction or abolition of inter-ectal discharges and eeg desynchronization was kept as goal of programming. All the patients were follow-up 6 months to 4 years. Significant seizure reduction observed immediately after programming. Two patients became seizure free. Three patients have 60–80% seizure control. One patient did not get significant benefit. In three patients (good respondent) after a period of two years seizure frequency increased following battery depletion that required replacement using respectable rechargeable DBS system. Above study shows effectiveness of anterior thalamic stimulation for intractable epilepsy. Better result can only be achieved by effective eeg guided programming. Prolonged follow-up with more number of cases is required to establish deep brain stimulation of anterior thalamic nuclei as safe and effective therapy for refractory epilepsy patients who are otherwise not suitable candidate for conventional epilepsy surgery.