Comprehensive Epilepsy Center
Fig. 1
Patient with a tumour in whom fMRI was performed to determine the area of expressive speech.
Professional in charge: Dr. DīGiano Carlos
From 25 to 30% of all patients with epilepsy are refractory to treatment with the appropriate drugs, during the necessary time and with the corresponding controls (clinical and serum levels). Refractoriness is due to the impossibility of achieving appropriate control of the disease; in other words, that the patient should not suffer any more epileptic seizures that affect him/her in his/her social and working sphere, as well as in quality of life.
Temporal lobe epilepsy is the most common form of epilepsy afflicting the adult population (75%), representing in children 40% of surgically treatable epilepsies.
* 1. Patient Selection
* 2. Prospective results for temporal epilepsy
* 3. Wada or sodium amytal test
* 4. Some Historical Facts
* 5. In the Imaging Era...
* 6. Vagal stimulation
* 7. Epilepsy and women
* 8. Medical team
1. Patient selection Return
All patients require conventional Video Electroencephalography (VEEG), which is of diagnostic use and contributes essential data to the treatment plan to be followed.
A small percentage of patients require Video EEG with intracranial electrodes, a technique indicated in those who show a discrepancy between clinical and neuroradiological findings (standard CT, MRI with protocol for epilepsy) and information afforded by conventional Video-Telemetry.
Video EEG with subdural electrodes is resorted to in patients with a neocortical component, or deep electrodes in cases where it is necessary to determine laterality.
2. Expected results for temporal epilepsy Return
The expectation of cure or significant improvement (Engel classes I and II) in temporal lobe surgery, both in adults and in children, according to the series published world-wide over the last 15 years ranges from 70 to 75%. In institutional experience, similar figures are corroborated with postoperative follow-up reaching 7 years.
Surgery is considered in two stages in cases where intracranial electrodes should be used. The first stage consists in subdural electrode placement by means of craniotomy (skin and bone flap), or of deep electrodes for implantation in cases where the laterality of the epileptogenic area should be studied. The second surgical stage corresponds to the treatment of the region, whether temporal,
hippocampal or the one responsible for generating the seizure.
It should therefore be pointed out that these patients require two surgeries, that is to say, two craniotomies with the corresponding surgical time for each one, blood transfusion requirement, with a potentially greater risk of infection, which prolongs their hospitalisation by roughly 48 hours. These patients always require intraoperative post-resection EcoG.
3. Wada or sodium amytal test Return
Preoperatively, it is performed in patients to be operated on for temporal and frontal epilepsies. It is useful to determine laterality in speech dominance and the capacity of both cerebral hemispheres to store memory. Over the last few years, attempts are being made to replace this technique by methods of Functional Magnetic Resonance Imaging (fMRI) in order to evaluate speech dominance non-invasively.
4. Some Historical Facts Return
Fedor Krusse in Berlin suggested surgical treatment not only for posttraumatic epileptic patients, but also for all those who presented focal epilepsy, even without demonstrable organic lesion. It was he who stimulated for the first time the motor cortex of a patient during surgery. He reproduced the aura and/or the patient's characteristic convulsive crisis, to learn then which was the area of the cortex that he should resect.
The first electroencephalographic (EEG) recording was obtained by Foerster and Altemburger and published in 1930. Contemporaneous neurophysiologists agreed on a new and fundamental concept: that EEG is suitable to determine the site of origin of a convulsive crisis.
In 1940, Von Wagenen had reported the results of the first ten callosotomies performed, as he stated, in an effort to avoid the propagation of the convulsive wave from one hemisphere to another.
At this stage, there were two main objectives of surgery for epilepsy:
1. to remove an eventual lesion together with the epileptogenic focus, and
2. to control the epileptogenic area by limiting the propagation of electric activity.
In the 1950s, attention was centred on temporal epilepsy. In 1957, the Montreal group communicated their experience in temporal lobectomy at the Second International Colloquy
in Bethesda.
There were still several challenging problems to determine the laterality of an epileptogenic focus. Video-EEG was the great contribution made by UCLA in the 1960s. Thus, clinical correlation with EEG became increasingly important, until attaining the role it plays nowadays. With its application, a reduction was achieved in the use of invasive procedures for the selection of candidates to surgery for epilepsy.
The substantial contribution of deep electrodes was to determine the laterality in apparently bitemporal epilepsies.
5. In the Imaging Era.... Return
Starting from what may be termed the Image Revolution, CT from 1974, MR, PET and SPECT (functional image) in the early 1980s, and functional and spectroscopic MRI in the 1990s, have enhanced the diagnosis of symptomatic epilepsy, with the lesion becoming more and more important as a guide to treatment of refractory epilepsies.
High field MR allows us to identify the impairment in neuronal organisation and migration such as lisencephalias, heterotopias, cortical dysplasias as polymicrogyrias, schizoencephalias,
megaloencephalias, cortical tubers or heterotopic neuronal inclusions of high epileptogenic potential that are observed in Bourneville's disease.
Mesial temporal sclerosis (described in the middle of the XIX century), a frequent finding in surgical specimens from operated patients by Falconer in the 1950s, gained diagnostic certainty with MRI.
Gradually, imaging replaced the complex, and at times risky, brain mapping (with evoked potentials and intraoperative EcoG). Lastly, spectroscopic analysis of the MRI (SMRI) currently allows determining with certainty the subnormal features of essential amino acid metabolism.
At hippocampal level, this helps to diagnose mesial temporal sclerosis.
Laterality determination of seizure origin, one of the key problems in epilepsy surgery, is resolved today with a high degree of certainty by means of MRI. Exceptionally, the use of intracranial electrodes becomes necessary.
Hours of Video-EEG recording hoping to capture the greatest possible amount of spontaneous convulsive crisis, in the search for the so-called electro-clinical correlate, together with the compatible pathological image, nowadays enable planning most surgeries, especially in the temporal lobe, without resorting to invasive methods. In such cases, the sodium amyobarbital test (Wada Test) helps us to define hemispheric speech and memory dominance, that conditions surgical technique in operations on temporal and frontal lobes.
During the last decade, the tendency has been to simplify presurgical diagnostic procedures.
Surgery as proven useful treatment for refractory epilepsies of the temporal lobe (70-80% cure at two years) was quickly extended to other areas of the brain. The Cleveland Clinic leads the trend in replacing, when necessary, deep intraparenchymal by subdural electrodes: that is, the placement of subdural electrodes (in array or grid form from 4 to 64 electrodes).
From 1978, S. Goldring (University of Washington) has successfully used them in small children, placing them in the epidural space.
The use of subdural electrode grids to obtain Video-EEG monitoring recordings radically changed the surgical treatment of neocortical epilepsy in the child and adult. Through simple orifices or craniotomies of diverse size, they may be placed in different areas of the encephalon, obviously helping to determine the primary epileptogenic focus.
In Argentina, well-known masters of Neurosurgery such as Drs. Carrea, Ghersi and Bocciardo, among others, successfully practised anatomical hemispherectomies in past decades.
The usefulness of surgery for epilepsy and its results are no longer under discussion throughout the world. Their implementation implies the organisation of a multidisciplinary team, where neurologists, neurophysiologists, neuropsychologists, neuropsychiatrists, neuroradiologists and neurosurgeons work in close collaboration.
6. Vagal Nerve Stimulation (VNS) Return
This represents a therapeutic alternative mainly for patients with focal epilepsies who are not candidates for the above mentioned surgeries. It has been practised world-wide during the last 10
years. Our centre has implanted more than five of such stimulators, whose results offer a 40-50% reduction in seizures in half of implanted patients, together with an improvement in the cognitive sphere.
7. Epilepsy and women Return
The Comprehensive Epilepsy Centre at FLENI has a special area devoted to assist women with epilepsy whose problem is of supreme complexity along their reproductive cycle. Thus, it is sought to offer them the best therapeutic alternatives, with special consideration for potential pregnancies and interactions of antiepileptic drugs with birth-control medication. The ultimate purpose of this area is to afford the woman with epilepsy, a special multifactorial assistance that includes in the case of conception an attempt to diminish significantly the risks of malformations in the new-born. In this clinic, emphasis is laid on the need to plan conception, which requires interdisciplinary work involving gynaecologists, obstetricians, geneticists and neurologists.
8. Medical Team Volver
Dr. D' Giano, Carlos
Dr. García, María del Carmen
Dr. Pociecha, Juan
Dr. Meischenguiser, Ricardo
Lic. Roca, María
Dr. Russo, Griselda
Dr. Pomata, Hugo
Dr. Petre, Cesar
Fig. 2
Right Mesial Temporal Sclerosis: Lesion in different MRI sequences.
Fig. 3
Spectroscopy with magnetic resonance imaging: Descent of a substance (NAA: N-acetyl aspartate in the affected hippocampus) within the lesion.
|
