Inferring Seizure Frequency From Brief EEG Recordings
*MGH Epilepsy Service, Massachusetts General Hospital, and Harvard Medical School, Boston, Massachusetts, U.S.A. †Sleep Division, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, U.S.A. ‡King Edward VII Memorial Hospital, and Department of Internal Medicine, Paget, Bermuda.Journal of clinical neurophysiology: official publication of the American Electroencephalographic Society (Impact Factor: 1.43). 04/2013; 30(2):174-7. DOI: 10.1097/WNP.0b013e3182767c35
: Routine EEGs remain a cornerstone test in caring for people with epilepsy. Although rare, a self-limited seizure (clinical or electrographic only) may be observed during such brief EEGs. The implications of observing a seizure in this situation, especially with respect to inferring the underlying seizure frequency, are unclear. The issue is complicated by the inaccuracy of patient-reported estimations of seizure frequency. The treating clinician is often left to wonder whether the single seizure indicates very frequent seizures, or if it is of lesser significance. We applied standard concepts of probabilistic inference to a simple model of seizure incidence to provide some guidance for clinicians facing this situation. Our analysis establishes upper and lower bounds on the seizure rate implied by observing a single seizure during routine EEG. Not surprisingly, with additional information regarding the expected seizure rate, these bounds can be further constrained. This framework should aid the clinician in applying a more principled approach toward decision making in the setting of a single seizure on a routine EEG.
Article: Patient awareness of seizures[Show abstract] [Hide abstract]
ABSTRACT: In 31 consecutive patients who were admitted to an epilepsy monitoring unit, we prospectively determined whether the patients were aware of having seizures. On admission, all patients stated that they knew of at least some of their seizures. Eight of 23 with classifiable epileptic seizures recognized that they were occasionally unaware of their seizures. During telemetry, following full recovery of consciousness after each seizure, we asked the patients whether they had recently had a seizure. For control purposes, we asked the patients the same question at random times. Among patients with seizures, there were no false-positive answers. Only 6 of 23 (26%) of the patients with epilepsy were always aware of their seizures, including complex partial and secondarily generalized events, and 7 of 23 (30%) were never aware of any seizures. Self-reporting of seizures was unreliable: Patients reporting the lowest baseline frequency of seizures had the highest fraction of unrecognized seizures. Seizure awareness was lowest for patients with temporal lobe foci, especially on the left side. Patients with primarily generalized epilepsy were more likely to be aware of tonic-clonic seizures than were patients with secondarily generalized partial seizures. All four patients with nonepileptic attacks believed that they always knew of their seizures, but only three of the four patients actually did always know. Unrecognized seizures are frequent and should be considered in patient management and in studies.Neurology 08/1996; 47(1):260-4. DOI:10.1016/S0736-4679(97)86443-8 · 8.29 Impact Factor
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ABSTRACT: Accurate knowledge of the frequency of epileptic seizures is a precondition for evaluating the efficacy of pharmacotherapy. It is a well-known fact that the information provided by epilepsy patients about the number of seizures they experience is often unreliable. In the present study, we aimed to identify predictors of a higher risk of unrecognized events. Thirty patients who underwent presurgical evaluation in a video/EEG monitoring unit were recruited. As soon as the patient became aware of a seizure, he or she completed a standardized questionnaire on the subjective perception of the seizure, which was then compared with the video/EEG findings. Of the 138 seizures recorded, 49.3% were reliably detected by the patient, whereas 44.2% went unnoticed; the remainder were incompletely or uncertainly perceived. Subjects in whom events occurred during sleep or originated in (or propagated to) the left temporal lobe had a significantly higher percentage of unrecognized events.Epilepsy & Behavior 10/2006; 9(2):281-5. DOI:10.1016/j.yebeh.2006.05.010 · 2.26 Impact Factor
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ABSTRACT: To evaluate the effects of a daily patient reminder on seizure documentation accuracy. Randomized controlled trial. Monitoring unit of an academic department of epileptology. Patients Consecutive sample of 91 adult inpatients with focal epilepsies undergoing video-electroencephalographic monitoring. Intervention While all patients were asked to document seizures at the beginning of the monitoring period, patients from the experimental group were reminded each day to document seizures. Main Outcome Measure Documentation accuracy (percentage of documented seizures). A total of 582 partial seizures were recorded. Patients failed to document 55.5% of all recorded seizures, 73.2% of complex partial seizures, 26.2% of simple partial seizures, 41.7% of secondarily generalized tonic-clonic seizures, 85.8% of all seizures during sleeping, and 32.0% of all seizures during the awake state. The group medians of individual documentation accuracies for overall seizures, simple partial seizures, complex partial seizures, and secondarily generalized tonic-clonic seizures were 33.3%, 66.7%, 0%, and 83.3%, respectively. Neither the patient reminder nor cognitive performance affected documentation accuracy. A left-sided electroencephalographic focus or lesion, but not the site (frontal or temporal), contributed to documentation failure. Patient seizure counts do not provide valid information. Documentation failures result from postictal seizure unawareness, which cannot be avoided by reminders. Unchanged documentation accuracy is a prerequisite for the use of patient seizure counts in clinical trials and has to be demonstrated in a subsample of patients undergoing electroencephalographic monitoring.JAMA Neurology 12/2007; 64(11):1595-9. DOI:10.1001/archneur.64.11.1595 · 7.42 Impact Factor
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