Emergent EEG: Indications and diagnostic yield

In a recent article, Varelas et al. 1 reviewed the indications and diagnostic yield of emergent EEG (EmEEG) and concluded that although EmEEG was ordered to rule out status epilepticus (SE) in 60.2% of cases, this diagnosis was performed in only 10.7% of patients. Their study was based on about 90% of cases of EmEEG requested in intensive care units, neurology, and neurosurgery services. We recently evaluated the role of EmEEG in a general hospital population. In the 1-year period (January–December 2002), 434 of the 2453 EEG performed in our service (17.7%) could be identified as EmEEG. Of those, 105 were performed in 53 adult inpatients (mean age 71.1 ± 14.9 years) of internal medicine and surgery departments (several patients had more than one EEG record). We reviewed the reasons for EmEEG requests and the impact of EmEEG in the management of these patients according to a slightly modified version of the guidelines proposed by Hillen and Sage. 2 The most frequent causes of EmEEG request were acute confusional states (38 cases) and unexplained brief loss of consciousness (13 cases). Many patients had more than one etiologic factor. Major metabolic derangements including diabetes and electrolyte imbalance, liver or renal impairment were present in 23 cases (43.3%). Nine patients (16.9%) had cardiac or pulmonary disease; 15 patients (28.3%) had cancer with toxic encephalopathies or metastatic complications; and 5 patients (9.4%) had postsurgical complications. The EmEEG showed abnormalities in 50 patients (94.3%) and was deemed useful in 45 (84.9%). EEG findings and clinical data suggested generalized nonconvulsive status epilepticus (NCSE) in 9 patients with acute confusional state and showed focal epileptiform discharges in 3 patients. In internal medicine and surgery departments, the symptom most frequently resulting in requests for EmEEG was a sudden onset of altered mental status. EmEEG were useful in the management of hospitalized patients in about 85% of cases, and epileptiform abnormalities were found in 22.6% of the 53 patients. NCSE is a condition frequently underdiagnosed and confounded by coexisting disorders, and EEG patterns are suggestive but not pathognomonic. 3 In contrast with a recent report, 4 we believe that there are no unique clinical features of NCSE and only prolonged and serial EEG may help the diagnosis—an integration of clinical data and EEG findings. 5 Despite the obvious importance of both neuroimaging and EmEEG, neither investigation can replace the neurologic consultation.