Mismatch negativity and late auditory evoked potentials in comatose patients

Objectives: The purpose of this study was to assess the patterns of mismatc h negativity (MMN) and N100 component in comatose patients and to evaluate their prognostic value vis-g-vis return of consciousness. Methods: MMN and auditory (early, middle-latency and late) evoked potential s were recorded in 52 normals and in 128 comatose patients (comas due to ne urosurgical and neurological problems). At the time of recording, all patie nts scored lower than 8 on the Glasgow scale. Results: Visually detected N100 and MMN were confirmed by cross-correlation of sub-averages. The MMN was present in 33/128 patients and the N100 compo nent in 84/128. The amplitudes of MMN and N100 waves detected in comatose p atients were statistically different from those of normal subjects. By 3 mo nths after the onset of coma, 95 patients had returned to consciousness, mo st of them with moderate to severe disability. A ratio of 30/33 patients wi th MMN and 70/84 with N100 had regained consciousness. The presence of a MM N together with a N100 component was more specific (90.9%) than the presenc e of a N100 component irrespective of MMN (57.6%) in terms of predicting re turn to consciousness, but its sensitivity was lower (respectively 31.6% fo r MMN and 73.7% for N100). The mean period that elapsed between the recordi ng of evoked potentials and a return to consciousness was 6.3 +/- 4 days. M LAEPs were also highly specific, but BAEPs were not. Conclusion: MMN and auditory evoked potentials provide a reliable assessmen t of the functional status of comatose patients. When present, MMN and the N100 differ from those found in normal subjects in terms of latencies and a mplitudes. As a predictor of return of consciousness MMN had high specifici ty and low sensitivity, whereas the N100 had high sensitivity and low speci ficity. This study demonstrates that the recording of MMN and the auditory N100 can be avery useful aid in the assessment of coma and in predicting wh ether or not a patient will regain consciousness. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.