Introduction: Guidelines from the National Institute for Health and Clinical Excellence (NICE) and the International League Against Epilepsy recommend long term EEG monitoring (LTM) in patients for whom seizure or syndrome type is unclear, and in patients for whom it is proving difficult to differentiate between epilepsy and non-epileptic attack disorder (NEAD). The purpose of this study was to evaluate this recommended use of LTM in the setting of an epilepsy tertiary referral unit.
Methods: This study reviewed the case notes of all admissions to the Sir William Gowers Unit at the National Society for Epilepsy in the years 2004 and 2005. A record was made of the type, duration and result of all LTM performed both prior to and during the admission. Pre- and post-admission diagnoses were compared, and patients were divided according to whether LTM had resulted in a change in diagnosis, refinement in diagnosis or no change in diagnosis. The distinction between change and a refinement in the diagnosis was made on the basis of whether or not this alteration resulted in a change in management.
Results: 612 patients were admitted during 2004 and 2005, 230 of whom were referred for diagnostic clarification. Of these, LTM was primarily responsible for a change in diagnosis in 133 (58%) and a refinement of diagnosis in 29 (13%). In 65 (29%) patients the diagnosis remained the same after LTM. In those patients in whom there was a change in diagnosis, the most common change was in distinguishing epilepsy from NEAD in 73 (55%) and in distinguishing between focal and generalised epilepsy in 47 (35%). LTM was particularly helpful in differentiating frontal lobe seizures from generalised seizures and non-epileptic attacks. Inpatient ambulatory EEG proved as effective as video telemetry in helping to distinguish between NEAD, focal and generalised epilepsy.
Discussion: The study revealed that LTM led to an alteration in the diagnosis of 71% of patients referred to a tertiary centre for diagnostic clarification of possible epilepsy. Although LTM is relatively expensive, time consuming and of limited availability, this needs to be balanced against the considerable financial and social cost of misdiagnosed and uncontrolled seizures. This service evaluation supports the use of performing LTM (either video or ambulatory) in a specialist setting in patients who present diagnostic difficulty.