Vegetative state and responses to sensory stimulation: an analysis of 24 cases

A meta-analysis was performed on data from 24 single-case experimental studies evaluating the immediate effects of sensory stimulation treatment on patients in vegetative state following traumatic brain injury. Response to treatment was evaluated by time sampling behaviour pre- and post-treatment, and examining for changes in behaviour that suggested increased arousal. In this analysis the relative effectiveness of different treatment protocols was examined. The effects of variables such as age, gender and time since injury on magnitude of behaviour change was examined; also whether there was a relationship between response to treatment and outcome in terms of whether patients emerged from vegetative state or not. Analyses showed that multimodal stimulation produced greater behavioural changes than unimodal stimulation, and the use of personally salient stimuli in multimodal stimulation the greatest changes of all. Age and gender both showed effects on the magnitude of the behaviour change, but time since injury did not. Patients who did not emerge from the vegetative state were no less likely that those who did to produce statistically significant changes in behaviour in response to treatment. The paper includes a discussion of general issues concerning vegetative state.