Reports Of Seizure Frequency May Be Inaccurate In Patients With Focal Epilepsy

"Seizures are the main symptom of epilepsy and the major target of its treatment," the authors write as background information in the article. "Accordingly, seizure frequency is the primary outcome measure for individual treatment and for clinical trials." Seizures can be detected objectively using video-electroencephalographic (EEG) monitoring; however, because this method is expensive, it is used only in certain patients for short time periods. Physicians most often ask patients to maintain seizure diaries.

Christian Hoppe, Ph.D., and colleagues at the University of Bonn Medical Centre, Bonn, Germany, studied 91 consecutive adult patients with focal epilepsy who were admitted to a video-EEG monitoring unit between Oct. 1, 2004, and July 31, 2005. The patients were outfitted with electrodes and monitored by video for an average of 4.5 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 with generalized epilepsy or a history of pseudoseizures were excluded from the study.

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--85.8 percent of all seizures that occurred during sleep were unreported, compared with 32 percent of seizures that occurred when patients were awake. Of the seizures recorded by video-EEG, 43.6 percent occurred during sleep, while only 13.9 percent of seizures reported by patients occurred during sleep.

"Patients activated the push-button alarm ahead of 51 seizures (8.8 percent) but failed to document 17 (33.3 percent) 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.

"The accuracy of seizure documentation was not correlated with neuropsychological performance, including verbal or non-verbal memory, verbal fluency and intelligence level, nor was it correlated with academic achievement," the authors write. "However, in a group comparison, perfect seizure documenters had better verbal memory performance and higher school education than did non-perfect documenters." Patients who were reminded to report seizures did not document them at a higher rate than patients who were not.

"In conclusion, patient seizure counts are not valid and reports of complete seizure freedom may need objective evaluation (e.g., regarding a driver's license)," the authors write.

Reference for journal article: Arch Neurol. 2007;64(11):1595-1599. 

Editorial: Patient Seizure Counts Still Useful if Properly Interpreted

The data from this study "starkly prove that, on average, patients report fewer than half of all their seizures," write Giridhar P. Kalamangalam, M.D., D.Phil., of the University of Texas Health Science Center, Houston, and colleagues in an accompanying editorial. "Further, exhorting patients to keep an accurate tally with seizure diaries and reminders is fruitless."

"Does all of this demolish the epileptologist's main interrogative tool, the question, 'How many seizures have you had over the past few weeks"'" they write. "No, we maintain. The authors' data themselves suggest how the question may be resurrected." Based on the percentages of unreported nighttime and daytime seizures in the study, average frequency based on patient reports can be calculated.

"For the individual practitioner, the main lesson is acknowledging the pitfalls of routine clinical questioning of patients with seizures, especially those with complex partial seizures," they conclude.

Editorial reference: Arch Neurol. 2007;64(11):1565-1566.