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Epilepsy Surgery
Surgical Management of Intractable Epilepsy

Epilepsy is one of the commonest neurological disorders. Approximately 70% of people with newly diagnosed epilepsy can expect to achieve seizure freedom within a 10-year period following diagnosis. Factors that predict favourable outcome include idiopathic or cryptogenic epilepsy and childhood epilepsy. Though the prevalence data from India is not available, it is estimated that the incidence of intractable epilepsy is around 6-7/1,00,000. Out of this more than 50% are suffering from secondarily generalized epilepsy that can benefit from surgery. By this estimate approximately 2.4 to 3.2 lac people suffering from intractable epilepsy can benefit from surgery.
 
    
Surgical treatment of epilepsy is a treatment option in patients whose seizures are not responsive to medications or for patients who are unable to tolerate medication side effects. Medication may not also be the preferred treatment for patients whose seizures are caused by structural abnormalities in the brain.
 
    
Patients with poorly controlled seizures of any age who are otherwise in good health are candidates for epilepsy surgery. Epilepsy surgery candidates are typically young adults. However, the current trend is toward early intervention in children to avoid many of the psychosocial consequences of growing up with epilepsy.
 
    
The Epilepsy Surgery Program at the Jaslok Hospital and research centre is managed by a group of specialist dedicated to the field of epilepsy. They include Epileptologist; Dr. Joy Desai, Neurophysiologists Dr. Firuza Wadia and Dr. Margi Desai, Neuroradiologist Dr. Srinivas Desai, Neuropsychologist and Neurosurgeon Dr. Paresh Doshi. It is a major referral centre of India that offers complete evaluation and surgical treatment for epilepsy.

The presurgical evaluation involves a detailed workup comprising of history, EEG, MRI video telemetry and neuropsychological assessment. In certain cases single photon emission computerized tomography and MRI spectroscopy are also utilized. The data collected from all these investigation is than utilized to pinpoint the epileptic focus. Once the focus is identified a strategy for surgical resection is planned. The various surgical procedures that can be undertaken for treatment of epilepsy are:
  • Temporal lobectomy - removal of the anterior temporal lobe including the medial temporal structures. This is the most common and rewarding of all the surgeries for epilepsy.(Fig. 1 & 2).

Fig. 1 Temporal lobe being exposed during surgery for temporal lobectomy
 
Fig. 2 Picture after the resection of temporal lobe

  • Extratemporal resection - removal of epileptogenic cerebral cortex or lesions (tumors, hamartomas, vascular malformations etc.) outside the anterior temporal lobe
  • Hemispherotomy - a recent modification of hemispherectomy in which the damaged, epileptogenic hemisphere is disconnected rather than removed. It is a much shorter operation than hemispherectomy, and is ideally suited for patients with significant atrophy of the damaged hemisphere. The common seizure disorder that respond to this procedure include Rasmussen’s encephalitis, Sturge-Weber syndrome, HHE syndrome and hemimegaencephaly.
  • Corpus callosotomy - Corpus callosum connects the right and the left cerebral hemisphere. Sectioning of the corpus callosum disconnects the two hemispheres and prevents the spread of seizures from one hemisphere to the other. The common seizure disorders that respond to this form of surgery include tonic and atonic attacks that are frequently seen in Lennox-Gastaut syndrome, multi centric complex partial seizures with secondary generalization, etc.(Fig. 3).
Fig. 3 - T1 weighted Coronal MRI showing a corpus callosotomy. The corpus callosum between the roofs of the lateral ventricles has been sectioned and the body of the left later ventricle is seen herniating through the section.


  • Multiple subpial transection - When the eplileptogenic lesion is located in a functionally important area like speech or motor power centre of the brain, it is not advisable to resect the same due to high risk of neurological deficit. In such cases transection of the cortex without removal of the epileptogenic zone by specially designed instruments can decrease the seizure frequency and intensity.
  • Vagal nerve stimulation - involves implantation of a stimulating electrode around the left vagal nerve and attaching it to a pulse generator which is implanted under the skin just below the collar bone. The pulse generator is programmed so that it may be turned on or off at specified times and so that the amplitude and frequency of stimulation can be modified as indicated.

    Results

    Surgical success depends on the type of surgery, but most patients are substantially improved.
    • Approximately 80 percent of patients who have an anterior temporal lobectomy are seizure-free one year following surgery, and 90 percent show marked improvement.
    • 70-80% of the patients having lesion excision have significant control of their seizures with 50% of them being seizure free. 
    • More than 50 percent of patients who have a corpus callosotomy are substantially improved where in others the frequency and the intensity of the seizures is decreased.
    • Seventy-five percent of patients who undergo functional hemisphotomy are seizure-free postoperatively, and 100 percent are improved. 
    • Preliminary data suggest multiple subpial transection maybe effective in decreasing seizures without causing a neurological deficit. 
    • Preliminary data suggest that certain patients with generalized seizure disorders may benefit significantly from vagal nerve stimulation.

    Epilepsy Surgical Protocol, JHRC

    Phase I
    • History and evaluation by Epileptologist
    • MRI and MR spectroscopy
    • EEG
    • Neuropsychology
    • Video telemetry
    • SPECT scan

    Phase II

    • Wada test
    • Invasive EEG recordings (Subdural and Depth electrodes) Corticography
    • Cortical stimulation and mapping