Surgery for Intractable epilepsy

         Epilepsy is a condition characterized by the occurrence of seizures which are transient alterations in consciousness resulting from abnormal electrical activity in the brain. The main treatment of epilepsy is always medical but in patients who are unresponsive to or intolerant of medical therapy or have a surgical cause (eg mesial temporal sclerosis), surgery becomes an option. It is very important to determine that all medical options have been exhausted prior to surgery. Usual surgical procedures include - resective (removing portions) surgery like lesionectomy, temporal lobectomy, corpus callosotomy,hemispherectomy. Another recent advance is vagal nerve stimulation.
       Temporal lobectomy is the most common surgery for epilepsy. Complex partial seizures of temporal lobe origin constitute 25% of all epilepsy and among this a third is refractory to medical management. Indications include intractability to medical management and concordance of clinical, radiology, electrophysiological and neuropsychological data. Structures removed include anterior lateral temporal neocortex (4cm), anterior 3 cm of parahippocampal gyrus, hippocampus and amygdala. The results are usually good with upto 70% patients becoming seizure free and upto 20% having improvement in seizure controll.
       Hemispherectomy is indicated in partial seizures with contralateral hemiplegia interfering with neurodevelopmental milestones and a resectable epilepticogenic focus. Eg. Sturge Weber syndrome, Ramussens encephalitis, Infantile hemiplegic epilepsy etc. Structures removed include the frontal, parietal, occipital and lateral temporal lobes. With complete hemispherectomy, upto 85% achieve seizure free status. Postoperatively CSF pathway obstruction can occur necessitating  shunt.
        Multiple subpial resection is indicated when the seizure focus is at or extending into eloquent cortex. The principle of tis procedure is that vertical transection of eloquent cortex does not produce any deficits. The main indications include: focus in eloquent cortex, Landau-Kleffner syndrome (epileptic aphasia), Epilepsia partialis continua and failed hemisperectomy in Rasmussens disease.
Multiple resections are done using the subpial transection hook. The results are usually good and 75% of patients with intractable seizures have upto 90% improvement.
       Corpus callosotomy involves division of the corpus callosum to prevent spread of seizure discharge. This will help in  preventing secondary generalization (spread) of the seizures. The main indications include poorly controlled generalised seizures but no primary focus can be demonstrated eg: Lennox-Gastaut syndrome, multi centric CPS with secondary generalization. Complete sectioning of corpus callosum is essential for good results; 80% 0f patients reported more than 50% reduction in seizure frequency. Sequele include reduced spontaneity of speech, non dominant limb apraxia which are transient and interhemispheric sensory dissociation.
      Vagal nerve stimulation is a new method being used because not all patients with medically refractory epilepsy are candidates for resective surgery. Resective surgery is not always an option for medically refractory seizures. Vagus nerve stimulation (VNS) is an adjunctive treatment for certain types of intractable epilepsy and major depression. Vagus nerve stimulation (VNS) is designed to prevent seizures by sending regular, mild pulses of electrical energy to the brain via the vagus nerve. Indications include patients who have failed surgery before, patients who require extratemporal surgery in eloquent area or corpus callosotomy or the patients’ choice.