Volume 3 #1 January/March 1996 -.:. Revista Medicina Interna
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Review Articles Surgical treatment of epilepsy Manuel Gongalves*, Rita Almeida** Abstract Antiepileptic drugs continue to be the mainstay of treatment of treatment, particularly for clearly defined, surgically remediable patients with epilepsy. However, we must have surgical therapy syndromes, such as mesial temporal lobe epilepsy and certain as an option for those patients who are not completely free of pediatric disorders. Epilepsy surgery has become an option to be seizures, and for those who are free of seizures but suffer toxic considered alongside various other medical treatment options. side effects. Advances in diagnostic testing and surgical tech- Key words: epilepsy, epilepsy surgery, temporal lobe epilepsy. niques have greatly improved the safety and efficacy of surgical Introduction of epilepsy in the general population, and secondly, The history of surgical treatment of epilepsy goes back because of the significant percentage of patients with to the nineteenth century, in 1886, when Victor Hor- poor control, although in recent years, several more sley performed the first documented cases of excision effective antiepileptic drugs (AEDs), with fewer side of an epileptic focus, at the National Hospital for the effects, have appeared. In the U.S., the estimated pre- Paralyzed and Epileptic in London1. His ability to valence of epilepsy is 4 per 1000 inhabitants, giving identify these foci was based essentially on the work a global population of more than 800,000 people of John Hughlings Jackson, and his new concepts of epilepsy carriers. Approximately 30-45% of patients seizure semiology, works that were later confirmed are in poorly controlled conditions, indicating some by David Ferrier through electrical stimulation of 350,000 potential candidates for other treatment the cortex of monkeys. However, it was the work of types. Given that only 12.5% to 25% of these patients Penfield and Jasper2 in the first half of this century, qualify for surgical treatment, the number of patients that were pioneering in the use of supplementary requiring surgery in the U.S. will be approximately neurophysiological information for presurgical evalu- 75,000 - 100.000.3-5 ation and surgery itself. Thus, a basic triad of factors Epidemiological data obtained by groups in Opor- involved in the performance of these surgeries (neu- to, Portugal, indicate that the prevalence of epilepsy rologist, neurophysiologist and neurosurgeon) was in the general population is 4.1 per 1000 inhabi- defined from the beginning, and the neuroradiologist tants, with an annual incidence of approximately was added later. 40/100,000. Extrapolating the same calculations for In recent years, surgical treatment of epilepsy has the Portuguese population, it is roughly estimated increase considerably3, both in terms of the number that there are at least 30,000 patients with focal sei- of places where it is practiced, and above all, in the te- zures and 2,700 eligible for surgery. 250 new surgical chnical advances that have been achieved in this area. candidates will be added to this number each year.6 This therapy assumes great significance, firstly, due to the prevalence and incidence of new cases Selection of candidates The first problem that arises is the selection of candidates for surgery. In addition to patients with epileptogenic intracerebral lesion, which is itself a reason for surgical intervention (tumor, MAV), the criterion more uniformly followed is the selection of patients with epilepsy that is refractory to treatment. However, today, some authors4,7 point to the existence *Resident to the Neurology Supplementary Internship of certain epileptic syndromes that a priori, always **Neurology Interim Assistant have a better prognosis with surgical treatment (as in Neurology Service, Santo Antonio dos Capuchos Hospital, Lisbon the case of mesial temporal sclerosis) and therefore PUBLICAÇÃO TRIMESTRAL 31 VOL. 3 | Nº 1 | JAN/MAR 1996 REVIEW articles Medicina Interna constitute a uniform indication for surgery. together, may give us an indication of the persisten- Refractory epilepsy to treatment is when the pa- ce of seizures, even with therapy that is considered tient presents an unacceptable frequency of epileptic adequate:9 seizures, even though they are taking adequate doses 1 - Frequency: daily or weekly focal seizures will of AED, or when there are unbearable side effects. probably be difficult to treat; if they develop into An unacceptable frequency must be defined in ter- outbreaks (cluster) this trend will be even greater; ms of seizures, and by the patient himself, because 2 – Early onset: early onset of seizures, particularly apparently similar conditions can have completely in childhood, means an increased risk that they will different impacts on the lives of different patients persist; children with very frequent febrile convul- (social repercussions, employment, family, inability to sions or status epilepticus with fever are more likely drive, etc.). In the final analysis, of the various actors to develop temporal lobe epilepsy as adults; involved in this problem (doctor, patient, family), the 3 - Secondary generalization: motor generalization patient himself is the one who can define, with greater of non-motor partial seizures and spreading to the accuracy, whether or not he has refractory epilepsy. motor cortex of extra limbic focus also constitute According to current convention5,8-10, however, additional risk factors; it is appropriate that each patient undergoes at le- 4 - Structural damage: this is, obviously, a risk factor; ast two 1st line AEDs (phenytoin, carbamazepine, 5 - Concomitant neurological changes: patients with sodium valproate, phenobarbital) in monotherapy, underlying neurological dysfunction have a higher up to the maximum doses, then in association and, likelihood of the epileptic crises persisting. subsequently, the patient should be introduced to Alongside all these indicators, some authors12,13 2nd line drugs (in particular, one of the new AEDs: also indicate that in the specific case of children, lamotrigine, vigabatrin, etc.). This process should certain epileptic syndromes, including West syndro- take place over a period of one year, preferably two, me and Sturge-Weber syndrome, should be viewed until the epilepsy is considered refractory. According as possibly requiring early surgical therapy for their to some authors, if the response is negative with the control. There are several case series14 that are al- two 1st line AEDs in appropriate monotherapy, the ready showing a better prognosis, both in terms of chances of controlling the seizures with associations seizure frequency, and in particular, regarding motor of drugs is around 15% to 20%.11 and cognitive development of children among those The type of epileptic crisis is also important when who undergo surgery, compared with other patients selecting patients. Stereotypical focal seizures, always treated medically. with similar characteristics, will probably correspond to a single epileptic focus, thereby comprising a group Some exclusion criteria should be weighed5 : with major indication for epileptic surgery. This is a) Relative contraindications especially true of patients with temporal lobe epilepsy. • Progressive neurological or medical disease; Focal epilepsy originated in other areas of the brain, • Behavioral changes that affect post-surgical reha- particularly the frontal lobe, present specific issues bilitation; to resolve. • Concomitant medical illnesses that significantly Other crises, however, due to the risk they repre- increase the risks of surgery; sent for some patients (in terms of morbidity and • IQ <70 (for focal resections); mortality), even if their frequency is not exceptionally • Changes in memory function in the contralateral high, may have indication for surgery. These include hemisphere; atonic seizures (drop attacks) and some other types of • Behavioral or intellectual changes that prejudice generalized seizures, namely tonic and tonic-clonic. the pre-operative evaluation; In this case, the appropriate surgical intervention • Active psychotic illness not related to the periictal (callosotomy) is not intended to treat the epilepsy periods. itself, but primarily, to stop the spread of electrical b) Absolute contraindications stimulation and, consequently, its generalization. • Generalized primary epilepsy; In the clinical evaluation of a patient, it is possi- • Minor epileptic seizures that do not interfere with ble to consider some biological indexes that, taken quality of life. Medicina Interna 32 REVISTA DA SOCIEDADE PORTUGUESA DE MEDICINA INTERNA REVIEW articles Medicina Interna Neurobiological considerations in epilepsy • Invasive; Once the patient is considered refractory to medical • Intraoperative. therapy (e.g., after 2 years of treatment with AED), the possibility of surgery should be considered immedia- Noninvasive tely, and if there are no important contraindications Background: a correct assessment of the anamnestic present, the process of pre-surgical evaluation should data collected from the patient or family is usually be initiated. This approach is even more important in essential in the initial characterization of epilepsy; children, especially younger children.15,16 this stage also includes an adequate review of therapy This urgency is linked to the fact that brain matu- to which the patient has previously been submitted, ration continues throughout childhood, and includes particularly AEDs. changes in neuronal