Resective Epilepsy Surgery: The Case for Early Intervention
Resective Epilepsy Surgery: The Case for Early Intervention
Abstracts & Commentary
Sources: Hennessy MJ, et al. J Neurol Neurosurg Psychiatry. 2001;70:450-458; Duncan JS. J Neurol Neurosurg Psychiatry. 2001;70:432.
Hennessy and colleagues retrospectively analyzed the outcome of en bloc temporal lobectomy in 80 epilepsy patients with focal lesions other than hippocampal sclerosis (HS). Using an actuarial approach, they found that the probability of achieving at least 1 year of seizure remission within 5 years of follow-up was 71%. This is comparable to the international experience for either temporal lobectomy or lesional epilepsy regardless of location. They also found that dysembryoplastic neuroepithelial tumors (DNET) were associated with favorable outcomes.
In an accompanying editorial, Duncan emphasizes the need for early evaluation of surgical candidacy. Comparing the finding of adverse outcome associated with long duration (> 10 years) of epilepsy, Duncan states that most surgical series have waited more than 15-20 years after the onset of seizures. In other words, most patients are referred for surgery too late for them to be in the best outcome group.
Commentary
The analysis of epilepsy surgery outcome reported here is somewhat limited. Extratemporal resections were not included, and the inclusion criterion of a neuropathologically proven focal lesion other than HS only applied to one-third of 234 consecutive cases of en bloc temporal lobectomies. Nonetheless, the conclusions drawn are likely applicable to temporal lobe epilepsy that is nonlesional or associated with HS.
In terms of clinical parameters that may have had an effect on postoperative outcome, Hennessy et al round up the usual suspects. As in other studies (many cited by the authors), these included perinatal complications, family history of epilepsy, febrile convulsions, seizure type and EEG features, and results of neuropsychological testing.
The most significant positive predictive features were duration of epilepsy less than 10 years and age at operation younger than 30, certainly not independent variables. These results support 2 controversial pathophysiologic hypotheses: first, that the determinants of pharmacological resistance may be established early in the natural history of epilepsy, and, second, that secondary epileptogenesis accounts for surgical failure when epilepsy is long-standing (or, in Gower’s words, "Seizures beget seizures"). Whatever pathophysiologic mechanisms are involved, a consensus is developing that epilepsy surgery should be offered early when appropriate.
In pursuing preoperative evaluation for surgery, one must first decide upon a definition of "medically intractable" epilepsy. This definition has become more critical in the last decade. Since 1993, 13 new antiepileptic drugs (AEDs) have been approved for use in the United States. While 5 of these represent new formulations of older agents and are thus less relevant in expanding treatment options, the others represent truly novel AEDs. Some of the newer drugs may be more effective than others for specific seizure types; the empirical spectrum of action in humans is evolving as we gain more clinical experience. Nonetheless, if a neurologist were to perform serial trials of each of the new AEDs on a given patient prior to initiating a presurgical evaluation, surgery could potentially be postponed for years, and the current study demonstrates that such a delay can worsen surgical outcome. If "adequate" seizure control can be obtained in only 60-70% of patients in trials of 3 "older generation" AEDs (Smith DB, et al. Epilepsia. 1987;28[Suppl 3]:S50-58; Mattson RH, et al. N Engl J Med. 1992; 327:765-771), there is no reason to believe that the newer agents will increase the likelihood (probably less than 10%) of seizure freedom in any given patient who has failed 2 or more AEDs. Prior to the current boom in AED choices, an NIH Consensus Conference (Leppik IE. Epilepsy Res. 1992;5[Suppl]:7-11) proposed "that a person be defined as having intractable epilepsy if any seizures occur while the person is documented as having an AED concentration (or dosage) of at least one standard medication in the usually effective range at the time of the seizure within one year after the onset of epilepsy." This definition should set the standard for when a patient should first be considered for epilepsy surgery.
Vagus nerve stimulation, the only other nonpharmacologic treatment option (other than the ketogenic diet, which is useful in a select few), should also be considered early in the treatment algorithm (Benbadis SR, et al. Neurology. 2000;55:1780-1784). Its main advantage is to allow a lower degree of invasive treatment with its disadvantage being the low rate of achieving complete seizure remission, relative to temporal lobectomy. Finally, it is worth re-emphasizing a point previously discussed in Neurology Alert: epilepsy can be a fatal disorder and achieving seizure freedom reduces mortality as well as morbidity (Labar DR. Neurology Alert 1996;14:44-45). Neurology Alert suggests that more consideration be given to the appropriateness of early resective surgery for epilepsy patients. Such treatment may well be life preserving, in addition to health sustaining. —Andy Dean
Dr. Dean is Assistant Professor of Neurology and Neuroscience, Weill-Cornell Medical College, Attending Neurologist, New York Presbyterian Hospital, New York, NY.
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