Clinical significance and outcome of subclinical status epilepticus in adults

We reviewed the medical records and the EEGs of all adults treated for status epilepticus (SE) in our center in 4 years. EEG detected subclinical SE in almost half (49%) of the 45 consecutive patients identified. Comparing patients with and those without subclinical SE, we noted that patients with subclinical SE were older (p = 0.02) and more likely to have focal brain lesions (p = 0.04). In the absence of focal brain lesions, subclinical SE was still more common in old adults (p < 0.01). Regardless of age, subclinical SE was more difficult to control than clinically overt SE (p = 0.001). Although 24% of all patients died in ≤60 days, late mortality was not associated with subclinical SE (p > 0.05). However, an association between late mortality and presence of focal brain lesions was suggested by a low p-value (0.053). Subclinical SE appeared on the EEG as frequent discrete seizure episodes in all but 3 patients. None of the patients had a progressive sequence of EEG patterns, as was reported in the literature. Initiation of treatment before EEG recording in most of our patients (82%) might have interrupted the sequential appearance of the EEG patterns.