The clinical significance of EEG cyclic alternating pattern during coma.

To define the clinical significance of EEG "cyclic alternating pattern" (ECAP). ECAP is the periodic presence of a high-voltage slow waves alternating with low voltage irregular faster activity. This term was first described in comatose patients in 1944. It has been less recognized and may be underreported since then. The clinical significance of ECAP in the state of coma remains unknown. We reviewed our prospective EEG database for consecutive patients studied over a period of 4 years (n = 4,819) looking for patterns consistent with ECAP. We reviewed the charts of the patients with the above EEG pattern to define the clinical setting and the eventual outcome. Eleven patients were identified. All patients identified were found to be in the coma state at the time of the EEG. The majority of patients (n = 10) survived the coma, and half returned to the community in good functional status. ECAP is seen rarely in comatose patients. Regardless of the cause of the coma, the presence of ECAP carries an overall good prognosis for both survival and recovery.