Auditory Stimulation of Comatose Patient : An Exploratory Case Study

A descriptive case study was conducted at one acute care medical center using one head injured patient who was unconscious for thirty-three days before testing. The study was done to provide descriptive information on the behavioral, physiological and electroencephalographic changes following a program of intermittent, repetitive, long-term auditory stimulation. A patient who appeared to be unconscious thirty-three days, who had no evidence of extensive cortical damage and who had no evidence of hearing difficulties participated. The experimental stimulation was applied by earphones and consisted of a tape recording of eight Christmas songs which were separated by four seconds of silence, the question. What is your name? , and another four seconds of silence. Stimulation was provided three times.a day for six days. Physiological, behavioral and electroencephalographic (EEC) data were collected twice a day for ten days (starting four days before the stimulation program) before, five minutes and one hour after experimental stimulation. Major behavioral changes occurred during the test period. Across the days behavioral changes after five minutes of experimental stimulation include the appearance of previously absent reflexes, equal and midline pupils from unequal and deviate pupils, resumption of oculocephalic reflex, return of visual fixation and following, and spontaneous blinking to auditory and tactile stimulation. Additional behavioral changes included spontaneous and purposeful motor activities of all extremities and head turning in response to auditory and tactile stimulation. Previously decerebration and flaccidity had been observed. The physiological change observed after five minutes of experimental stimulation was a drop in blood pressure. Across the days behavior changes after one hour of experimental stimulation were similar to those after five minutes. Some reflexes tended to be absent on prestimulation and after one hour of stimulation but present after five minutes. Spontaneous movement, after one hour and before neurological testing, tended to be quiescent and similar to prestimulus observations. Behavioral and physiological data indicated no trend changes following loud auditory stimulation. Two hours after intra-abdominal gastrostomy tube insertion with a local anesthetic prestimulus behavioral changes demonstrated regression and depression. After stimulation all behavior returned to the previous days\u27 findings except spontaneous movements and responses to auditory stimuli. both of which remained conspicuously absent. During hypoxemia behavioral data demonstrated generalized depression of spontaneous behavior and regression of those reflexes elicited. Greater arousal levels were obtained after stimulation. Gradual EEG visual changes were noted across days. No specific remarkable changes occurred after any stimulation period. By the end of testing the EEG demonstrated better formed, better organized and higher frequency waveforms. Spectral analysis of the EEG demonstrated a gradual trend toward increased intensity and increased frequency activity across the days of testing. After five minutes of stimulation there was a tendency for increased intensity of all frequencies with no remarkable shift of the dominant frequency. Underlying mechanisms which were considered as contributing to the physiological, behavioral and EEG changes included variations in cerebral blood flow, alterations in metabolic demands, dendritic spine and bouton regeneration, habituation and hypoxia