At least 20% of epilepsy cases remain intractable even with the best medication treatment that in addition often lead to very disturbing side effects.
The consequences of this include: denied driving license, social isolation, job loss and, more importantly, real life threatening situations due to the injuries produced by the patient’s seizures.Recurrent seizures cause neuronal loss function, which almost always results in the deterioration of the memory function. It is particularly damaging in early childhood where repeated seizures stop psychomotor development.
It is a priority to control seizures before the child reaches eight years of age, at which point the brain has almost completely developed, in order to avoid permanent psychomotor impairment. When seizures remain refractory for more than one year, a presurgical evaluation is recommended. The main component of this evaluation is a video-EEG monitoring during several days to allow seizure recording for computerized analysis in order to disclose and localize the origin in the brain of those seizures.
Other components of the presurgical evaluation are:
– Brain imaging particularly MRI with special protocols.
– Metabolic functional imaging techniques such as PET or SPECT that overlap with the MRI.
– SISCOM (when needed).
– Computerized reformatting techniques of brain electrical activity (EEG) to localize electric dipoles that are superimposed on the MRI.
– Magnetoencephalography (MEG) to show the magnetic dipoles of seizure activity on the RM.
– Neuropsychological evaluation.
When the presurgical evaluation discloses a unique epileptogenic zone as the origin of the patient’s seizures, and has no functional risk of resection and correlates with a morphological abnormality detected on MRI, the patient is a good candidate for resective epilepsy surgery with excellent prognosis.
Epilepsy Surgical Procedure
Many patients are diagnosed of Temporal Lobe Epilepsy (or other forms of partial epilepsy) with very good surgical prognosis, and could proceed to a resection of their epileptogenic area, frequently an anterior temporal resection or an amigdalo-hypocampectomy. We started the epilepsy surgery program in 1987 and since then we have treated over 600 patients using different surgical techniques with results within international standards. Our experience is particularly broad and with exceptional results in difficult cases of children with tuberous sclerosis.
There are different surgical techniques that apply specifically to the different diagnoses of the patients undergoing epilepsy surgery, and also have different prognoses according to these diagnoses. The most common are: minimally invasive craniotomy with cortical resection (epileptogenic area) in the temporal lobe, selective amygdalohippocampectomy and frontal lobe resections. Resective surgery can be performed in any location of the brain, provided cortical functional localization is used to tailor it. Functional hemispherectomy is very useful in pediatric epilepsy with unilateral motor deficit.
Other palliative surgeries are: corpus callosotomy, vagal nerve stimulation, and DBS (Deep Brain Stimulation) stimulation (anterior thalamic nucleous). Palliative surgery is mainly designed to prevent sudden falls with injuries. Since the introduction of computer-guided surgery at our center in 1997, intraoperative neuronavigation has greatly facilitated the registration of any brain structure that is required. It has facilitated the identification of brain areas to preserve their functional importance and the location of any anomaly that has small size. Some cases need an awake craniotomy to study the cortical activity, and localize speech cortical areas and subcortical pathways to preserve brain function.
Groups with better prognosis after epilepsy surgery are:
Intractable epilepsy associated with a small lesion as benign tumors or vascular malformations. In this group 87% of patients remain seizure-free when the removal of the lesion and the epileptogenic area is performed. Another set of excellent results is medial temporal lobe epilepsy with mesial sclerosis, the most common type between the non-lesional epilepsies treated surgically, with over 70% of seizure-free cases.
Pediatric epilepsies associated to unilateral brain atrophy and hemiplegia treated by functional hemispherectomy reached more than 85% seizure-free. Non-lesional extratemporal epilepsies have a worse prognosis, but still a benefit is obtained from an improved quality of life in 75% of cases and the seizure-free patients arrive to 50%.
Complications are rare, with a mortality rate of less than 0.5%, which is much lower than the mortality figures for injuries sustained during the seizures observed in drug-resistant patients left to their evolution without surgery.
In our experience, for example there are 12 times more deaths from accidents in patients with uncontrolled seizures than in the surgical series. From 1987 to 1997 our team performed 234 intractable epilepsy surgical therapeutic and diagnostic procedures. From 1997 to 2012 we performed 372 additional epilepsy surgery procedures with large increase of complex cases without visible lesions in cranial MRI or multiple lesions in the cases of tuberous sclerosis. We can account for a total of over 600 procedures, accumulating the most extensive experience in Spain and one of the largest in Europe.
Epilepsy Surgery and Intracranial Recording Studies:
Some patients need a further evaluation during several days with intracranial implanted electrodes to disclose the seizures origin between two possible zones, which are not discernible from the study performed with scalp electrodes. Additionally, stimulation studies are performed to localize functions in cortical areas of the brain. In these cases a first operation is performed to implant the electrodes, and a second one to withdraw the electrodes and resect the seizure origin zone.
Intracranial recordings are performed with depth electrodes implanted with the neuronavigation system in different brain’s areas to allow an SEEG (stereo-encephalography) recording or with subdural grid, when a more localized area of the brain has to be studied and cortical functional mapping is needed.