Routine EEG vs. intensive monitoring in the evaluation of intractable epilepsy

Appropriate treatment of patients with intractable seizures requires precise identification of the type (or types) of seizure the patient experiences and correlation of this information with data from electroencephalography localizing the focus of the seizure in the brain. For such patients, the technique of "intensive monitoring" has gained rapid acceptance in the past several years as the investigative method of choice.Intensive monitoring usually entails prolonged electroencephalographic recording with simultaneous videotaping of the patient. Another common technique is prolonged monitoring of the patient's electroencephalogram (EEG) by radiotelemetry, during which time the patient is closely observed by trained personnel for suspected seizures.To compare the quality of information obtained from intensive monitoring with that from careful routine electroencephalography, the authors reviewed the medical records of 100 consecutive patients who had received both kinds of study after being referred for treatment in the special Epilepsy Treatment Unit of the University of Minnesota's Comprehensive Epilepsy Program (CEP).Success of each method was defined by ability to record an actual seizure. The routine EEG examination recorded actual seizures in 7 percent of patients in the study. With video EEG, following careful withdrawal of anticonvulsant drugs, seizures were recorded in 70 percent of patients. Telemetered EEG recorded seizure activity in 50 percent of those patients for whom the other two methods had failed to detect seizures.Intensive monitoring revealed that 60 percent of patients for whom the routine EEG study had recorded only one seizure type actually suffered from two or more types. Clinical diagnosis was changed in 84 percent of the patients. In this study, intensive monitoring was found to be far superior to the routine EEG examination as an aid to precise diagnosis of intractable seizure disorders.