Abstracts

Rationale: A Cochrane Review of pharmacological interventions for epilepsy in patients with intellectual disability (ID) concluded that in general, anti-epileptic drugs (AEDs) with proven effectiveness in the general epilepsy population will also be effective in patients with ID and will have similar side effects. The intention of our study was to determine whether prescribing practices at a tertiary epilepsy centre are consistent with this conclusion or whether there are differences in the choices of AEDs for patients with ID versus those with normal intellect (NI).Methods: A retrospective review of medical records of patients who attended the Epilepsy Clinic at Toronto Western Hospital, University of Toronto was conducted. All current and past AEDs that had been prescribed for chronic epilepsy were recorded. Forty-two patients with ID and a seizure disorder were compared to a control group of 32 patients with normal intellect (NI) and temporal lobe epilepsy (TLE). Multiple Chi-square tests were used to compare the two groups in terms of their exposure to various AEDs.Results: The two groups were comparable in terms of duration of seizure disorder as well as proportion with current seizure control. On average, the patients with ID were currently taking a greater number of different AEDs (p=0.003) and had been exposed to a greater number of AEDs in the past (p=0.007). There were no significant differences between the two groups in terms of the past or present exposure to the new AEDs as a group (including lamotrigine, topiramate, levetiracetam, gabapentin, felbamate and tiagabine) or to the old AEDs phenobarbital, primidone, phenytoin, ethosuximide, carbamazepine, or valproic acid. There was a significantly greater proportion of patients with ID who were currently taking (RR=1.6, p=0.01) and who had previously taken (RR=1.75, p=0.06) benzodiazepine (BZD) derivatives (clonazepam, nitrazepam, and clobazam) for chronic seizure control.Conclusions: The perfect equilibrium between best seizure control and tolerable side effects is difficult to obtain in patients with severe epilepsies. In this work we observed that patients with ID are equally exposed to the old and new generation of AEDs as those patients with NI-TLE. Interestingly, intellectually disabled patients take a statistically significant higher amount of BZD to obtain best seizure control compared to patients with NI-TLE. We speculate that the reasons for these findings are one of the following: 1. higher efficacy of BZD against seizures in patients with ID (atypical absences, tonic, atonic, etc) compared to partial-onset seizures seen in patients with NI-TLE. 2. higher tolerance of sedative side effects by parents or caregivers of patients with ID. 3. tacit approval and utilization of sedative side effects to manage patients that may have behavioural issues associated with their ID. Further analysis will be necessary to determine why patients with ID take higher amounts of BZD.