Criteria for the classification of carpal tunnel syndrome for use in epidemiologic studies were developed by means of a consensus process. Twelve medical researchers with experience in conducting epidemiologic studies of carpal tunnel syndrome participated in the process. The group reached agreement on several conceptual issues. First, there is no perfect gold standard for carpal tunnel syndrome. The combination of electrodiagnostic study findings and symptom characteristics will provide the most accurate information for classification of carpal tunnel syndrome. Second, use of only electrodiagnostic study findings is not recommended. Finally, in the absence of electrodiagnostic studies, specific combinations of symptom characteristics and physical examination findings may be useful in some settings but are likely to result in greater misclassification of disease status.

Summary:Although the causes of cognitive impairment in patients with epilepsy have not been completely elucidated, three factors are clearly involved: the underlying etiology of epilepsy, the effects of seizures themselves, and the central nervous system effects of antiepileptic drugs (AEDs). All commonly used AEDS have some effect on cognitive function, and the effect may be substantial when crucial functions are involved, such as learning in children or driving ability in adults, or when alreadyvulnerable functions are involved, such as memory in elderly patients. The available evidence is insufficient to support definite conclusions about the cognitive effects of three of the newer AEDs, tiagabine, gabapentin, and levetiracetam. Better evidence is available for lamotrigine (LTG), topiramate (TPM), and, to a lesser degree, oxcarbazepine (OXC). OXC appears not to affect cognitive function in healthy volunteers or adults with newly diagnosed epilepsy, but its cognitive effects in children and adolescents have not been systematically studied. A relatively large number of studies are available for LTG, which has demonstrated a favorable cognitive profile overall, both in volunteers and in patients with epilepsy. Although dose and titration speed may be confounding factors in some of the studies of TPM, there is clear evidence that this agent does affect cognitive function, with specific effects on attention and verbal function. For LTG, attempts have been made to correlate cognitive effects with what is known of the drug's mechanism of action; this is an area of research that deserves further exploration with regard to other AEDs as well, especially TPM. Key Words: Antiepileptic drugs-Cognitive function-Lamotrigine-Topiramate-Oxcarbazepine.Cognitive impairment is a frequently occurring secondary consequence of epilepsy (1,2).Cognitive function is higher-order behavior involving the capacity of the brain-specifically of the cortical structures-to program adaptive behavior, to solve problems, to memorize information, and to focus attention (3). Epilepsy is a result of ictal and interictal cortical dysfunction, and the possibility that cognitive impairment develops as a secondary symptom is thus obvious. Memory impairments, mental slowing, and attentional deficits are the most frequently reported cognitive disorders (4,5). Sometimes, such consequences are more debilitating for the individual patient than the seizures; thus, it is worthwhile to explore the factors that lead to cognitive impairment. The exact cause of cognitive impairment in epilepsy has not been explored fully, but three factors clearly are involved: etiology, the seizures, and the "central" side effects of drug treatment (6). Here we concentrate on the unwanted effects of antiepileptic medication on cognitive function. When evaluating this factor separately, it is imperative to realize that in clinical practice most cognitive problems have a

A drug that is only modestly efficacious but has a favourable safety profile may look better than a drug that is more efficacious but produces clinically meaningful adverse events. Therefore, a drug's retention rate is mainly determined by its side effect profile. As a consequence, retention rate was highest for lamotrigine and lowest for topiramate. Intermediate retention rates were seen with levetiracetam use.

For the treatment of patients with chronic refractory epilepsies, information about the long-term efficacy and safety profile of any new antiepileptic drug is crucial. Topiramate has been proven to be effective in patients with refractory chronic partial epilepsies in short-term controlled clinical trials, but the long-term retention, long-term efficacy, and long-term side-effect profile have not been sufficiently investigated. We analyzed all patients who had been treated with topiramate in the Epilepsy Centre Kempenhaeghe from the introduction of the drug in the spring of 1993 up to a final assessment point in mid-2002. In total, 470 patients were identified. The data show that the clinical dose achieved was about 200mg/day, reached after approximately 6 months of treatment. Further dose escalation in the survivors was slow, with a mean dose of about 300 mg/day after 24 months of treatment. Mean titration dose is 25mg/week, but titration strategy is mostly individual and responds to patient complaints. With respect to seizure frequency, 10-15% of the patients were seizure-free at the 6-month evaluation; 4 patients achieved a 2-year remission. Retention rate was 53% after 1 year, 45% after 2 years, 38% after 3 years, and 30% after 4 years. At 4 years, almost 70% of the patients had discontinued topiramate. The main reason was adverse events, which accounted for about 65% of the discontinuations. Behavioral side effects were dominant, with mental slowing (27.6%), dysphasia (16.0%), and mood problems (agitation: 11.9%) being the most frequently reported side effects. In about 10% of the patients side effects led to discontinuation despite the obvious favorable effects on seizure frequency. Comparisons between the patients who discontinued topiramate treatment and those who continued topiramate showed that discontinuation was associated with comedication (vigabatrin and lamotrigine). Our conclusion is that TPM is associated with a high incidence of side effects in clinical practice, affecting long-term retention. Meaningful prognostic factors that may help us in clinical decision making, i.e., to prevent the side effects or to help us identify those at risk, have not been found.

The retention rate for LEV is significantly higher than for TPM. LEV had a more favourable side effect profile than TPM with comparable efficacy. Patients on TPM discontinued treatment mainly because of neurocognitive side effects. In the treatment with LEV, the effects on mood must not be underestimated.