A comparison of a behavioural assessment tool and electrophysiological measures of recovery from coma

The Wessex Head Injury Matrix (WHIM) [1] is one of the rare behavioural scales that have been designed to follow the recovery of head-injured patients throughout the whole spectrum of altered states of consciousness, from exit of coma to complete recovery. In this study, we explored the validity of the WHIM in relation to other behavioural assessment tools – Glasgow–Liège Coma Scale (GLS) [2], Coma-Near Coma scale (CNC) [3], Western Neuro Sensory Stimulation Profile (WNSSP) [4] – as well as in relation to the Bi-Spectral Index (BIS), derived from electroencephalographic measures. Twenty-nine brain-injured comatose patients (aged 21–83 years) were followed longitudinally with these behavioural and electrophysiological measures. Overall, the evolution of the scores on the WHIM correlated significantly with the evolution of scores obtained by the GLS (r = 0.88; P < 0.01), the CNC (r = -0.8; P < 0.01), the WNSSP (r = 0.87; P < 0.01), as well as with the BIS measure (r = 0.58; P < 0.01). Relative to the GLS, CNC and WNSSP, the WHIM showed a particularly good sensitivity for documenting subtle changes in recovery for patients in a minimally conscious state. The BIS index globally evolved in parallel to the behavioural scales. However, it showed a very bad sensitivity as many patients in a coma or a vegetative state presented BIS scores that were as high as those observed for patients that had regained normal consciousness. The results confirm the usefulness of the WHIM, especially for the assessment of minimally conscious patients. However, even if a global relation is observed with behavioural scales, the validity of electrophysiological measures such as the BIS index is unsatisfactory for the assessment of altered states of consciousness.