Evaluation of ambulatory cassette EEG monitoring: III. Diagnostic accuracy compared to intensive inpatient EEG monitoring.

We assessed the ability to recognize epileptiform abnormalities on a video review of ambulatory cassette EEGs (A/EEG) by comparing two independent interpretations of an A/EEG to those derived from a routine recording and intensive monitoring by cable telemetry (C/EEG) of the same 40 patients. Both A/EEG readings concurred with the C/EEG interpretation as to normality or epileptiform abnormality in 77% of cases. Seventy-nine percent of focal and 100% of generalized interictal abnormalities, as well as all seizures, noted on C/EEG were detected by both A/EEG reviewers. Of patients with normal baseline EEGs, 37% showed epileptiform features on A/EEG versus 44% with C/EEG. Limits to the characterization of abnormalities by A/EEG and a protocol for the video review of A/EEG tapes are discussed. In those specific areas for which intensive surface EEG monitoring is most useful, ambulatory cassette EEG appears to be an acceptable intermediate-level alternative.