Reports of seizure frequency may be inaccurate in patients with partial epilepsy

Asking people who have partial seizures how often they have seizures does not appear to provide an accurate count, according to a report in the journal Archives of Neurology.

The report suggests that reminding patients to record their seizures in a diary may not help, because patients may be unaware of some seizures.

The authors write that seizure frequency is the primary outcome measure for individual treatment and for clinical trials. Seizures can be detected objectively using video EEG (electroencephalogram) monitoring; however, because this method is expensive, it is used only in certain patients for short time periods. Doctors most often ask patients to keep seizure diaries.

Dr Christian Hoppe and colleagues at the University of Bonn Medical Centre studied 91 adult with partial seizures who were admitted to a video-EEG monitoring unit in 2004 and 2005. The group were fitted with electrodes and monitored by video for an average of 4½ days. All were asked to keep a seizure diary and to push a warning button summoning a nurse when they felt a seizure coming. About half (42) were randomly assigned to receive daily reminders about documenting all seizures during the monitoring period.

Patients experienced a total of 582 partial seizures during monitoring but did not report 323 of them. Patients' level of consciousness before the seizure appeared to affect their reporting rate - 85 per cent of all seizures that occurred during sleep were unreported, compared with 32 per cent of seizures that occurred when patients were awake. Of the seizures recorded by video-EEG, 43 per cent occurred during sleep, while only 13.9 per cent of seizures reported by patients occurred during sleep.

"Patients activated the push-button alarm ahead of 51 seizures (8.8 per cent) but failed to document 17 (33.3 per cent) of these seizures," the authors write.

Reporting also varied by seizure type. Fifty-one percent of patients did not document any complex partial seizures, which arise from a single brain region and impair consciousness; a total of 73.2 percent of these types of seizures went unreported. This compares with 26.2 percent of simple partial seizures-which do not affect awareness or memory - that were not reported.