Postanoxic alpha (theta) coma: a reappraisal of its prognostic significance

Abstract

Objectives: To appraise the controversial prognostic significance of postanoxic alpha or theta coma (ATC). Methods: We prospectively assessed 14 comatose patients with ATC after cardiac arrest by means of a protocol which included repeated clinical examinations, EEG, and median somatosensory evoked potentials (SEP). Good outcome was defined by the reappearance of cognition (Glasgow outcome scale 3–5) at any time during the 1 year follow-up. Results: Nine of 14 patients had a monotonous, frontally accentuated and areactive alpha (theta) EEG activity (complete ATC). In these patients ATC was recorded a mean of 47 h after resuscitation, the mean Glasgow coma scale (GCS) was 4 at 48 h, and early cortical SEPs were altered or absent in 5 of 7 patients. All nine patients died. In five of 14 patients the alpha (theta) EEG activity was either not monotonous, partially reactive or posteriorly dominant (incomplete ATC). In these patients ATC was recorded a mean of 43 h after resuscitation, the mean GCS was 8 at 48 h, and early cortical SEP were normal in 4 of 5 patients. Three of 5 patients regained cognition, two of them remained however dependent in activities of everyday life. Conclusions: This study and a review 283 cases of postanoxic ATC reported in the literature suggest the existence of incomplete and complete variants of postanoxic ATC. Whereas complete ATC is invariably associated with a poor outcome, full recovery is possible in patients with incomplete ATC. The combination of EEG, clinical, and SEP findings improves the prognostic accuracy of postanoxic ATC.