Clinical and EEG features of status epilepticus in comatose patients.

We retrospectively evaluated the clinical and EEG features of status epilepticus (SE) in 47 comatose adult patients in whom SE was suspected clinically or because the EEG revealed repetitive electrographic seizures or continuous spike-and-wave activity. Three groups of patients were identified. Group-1 patients (n = 33) had SE both clinically and on EEG. They usually had subtle, clonic movements restricted to the eyes, face, and upper extremities, and the EEG most commonly showed repetitive electrographic seizures or continuous spike-and-wave activity. Group-2 patients (n = 9) also had subtle motor manifestations of seizures, but the EEG was not that of SE, consisting of either irregular slowing with frequent spikes and sharp waves, an irregular mixed-frequency background with episodic accentuation, or diffuse slowing; one patient also had an intermittent burst-suppression pattern. The five patients in Group 3 lacked any clinical signs of seizures, but the EEG showed repetitive electrographic seizures or continuous spike-and-wave activity. There were no significant differences between groups in etiology of SE, response to therapy, or outcome, and there was no obvious relationship between the EEG findings and duration of SE. We conclude that recognition of SE in comatose patients may require both clinical and EEG evaluation since either approach by itself may fail to establish the diagnosis. Furthermore, the EEG findings in established SE do not necessarily progress through the series of defined stages suggested by some authors.