Abstracts

Rationale: About a quarter of patients with epilepsy are refractory to medical treatment. Anecdotally, such patients demonstrate fluctuations in seizure frequency which is independent of medical intervention but objective evidence of this is lacking. Statistical Process Control (SPC) is the continuous monitoring and charting of a process while it is operating, to warn of when the process is moving away from predetermined limits. It has been used in manufacturing for many years as a tool for quality control and could potentially be used to provide evidence for seizure fluctuation in patients with chronic epilepsy. The aims of our study were to; (1) objectively demonstrate fluctuations in seizure frequency in patients with intractable epilepsy using SPC charts and (2) assess whether observed seizure fluctuations are influenced by drug manipulations. Methods: Clinical data from thirty-eight randomly selected young people with intractable epilepsy attending a residential school for young people with epilepsy were retrospectively collated. SPC charts were generated using SPSS version 14 (Chicago, Illinois) to map weekly seizure frequencies. Two paediatric epileptologists blinded to clinical and demographic data independently assessed the SPC charts to predict from the observed seizure pattern whether drug manipulations were made and the timing of such manipulations. Results: All study participants had fluctuation in seizure frequency overtime demonstrated by SPC charts (Figure 1). Twenty-eight (0.737; 95%CI 0.58-0.85) had drug manipulations during the study period but there was inter-rater agreement on whether there were drug manipulations and their timing on SPC charts in only three subjects (kappa-0.15, p-0.4), only one of which had a drug manipulation followed by a change in seizure frequency (Figure 2). Of the others, one had not had a drug change and the other had drug manipulation at a time distant from that predicted. Conclusions: In this group of young people with intractable epilepsy fluctuations in seizure frequency was rarely modified by drug manipulations. SPC charts can be used to provide objective evidence of fluctuations in seizure frequency in young people with intractable epilepsy thereby avoiding unnecessary drug manipulations in response to short term fluctuations.