P300 evoked by the patient's name as a predictor of recovery from coma

Abstract

An assessment of event related potentials in response to a series of clicks or tone bursts has been shown to be a highly specific predictor of recovery from coma caused by head injury.1 There is anecdotal evidence that patients in coma may be roused by emotionally significant stimuli like the sound of their own name. In non-attending normal subjects, the electrical response to the sound of their own name among a series of abstract tones includes both the ‘mismatch negativity’ (a protracted negativity following the N1 component of the auditory evoked response) and subsequently a P300. The latter is generated by mechanisms involved in recognizing the meaning of a stimulus. We hypothesized that such stimuli may be more powerful probes of residual function and thus more sensitive predictors of recovery from coma than responses to simple tones. We recorded the responses to tone bursts interspersed at irregular intervals with the person's name (spoken by a relative) in 21 patients in coma (Glasgow Coma Score (GCS) ≥8 post-resuscitation) due to head injury (14), subarachnoid haemorrhage (6) and hepatic encephalopathy (1). Mean GCS on admission of the 21 patients was 4.4 (SD2.0). The initial recording was made within 3–4 days of onset, and subsequent recordings were made twice weekly until recovery of consciousness or treatment was withdrawn. Outcome was assessed at 6 months on the Glasgow Outcome Score (GOS). Of the 12 patients who survived, five had a GOS of 5 (Good Recovery), five a score of 4 (Moderate Disability) and two had a score of 3 (Severe Disability). Table 15 shows the incidence of P300 evoked by the patient's name in those who survived and those who died. Eventually it was present in all but two who made a good recovery and none of those who died. All of those in whom P300 was present survived; however its absence early in coma is not predictive.