Relation Between Asymmetry of Prefrontal Activity and Autonomic Nervous System in Post-stroke Patients with a Disorder of Consciousness

Abstract

Early mobilization and rehabilitation of stroke patients can improve functional recovery. However, effects of mobilization on the responses of the autonomic nervous system (ANS) and emotions in post-stroke patients are not yet clear, particularly in patients with disorders of consciousness. We evaluated the effects of standing load on the ANS and emotions of post-stroke patients (n = 8, 70.8 ± 11.8 years) with a disorder of consciousness by measuring the prefrontal cortex (PFC) activity, which plays important roles in regulation of the ANS and emotions. Employing near infrared spectroscopy (NIRS), we measured concentration changes of oxygenated haemoglobin (oxy-Hb) in the PFC for 10 min at rest. Then, subjects were placed in supine position on a tilt table, and standing loads were given by 30°, 45° and 60° every 5 min. We assessed left-right asymmetry of the PFC activity at rest by calculating the Laterality Index at Rest (LIR; LIR>0 indicates right dominant activity while LIR<0 indicates left dominant activity). We observed fluctuations of oxy-Hb in the PFC at rest, indicating activation of the PFC. Interestingly, 75% (six patients) of the patients exhibited right dominant PFC activation at rest. These patients exhibited an increase of oxy-Hb during standing load; four patients suffered from orthostatic hypotension. Finally, there was a significant positive correlation between LIR before the standing test and oxy-Hb changes during the standing test (r = 0.78, p = 0.02). These results suggest that the standing load might act on post-stroke patients as a stressor, which caused an increase of PFC activity (i.e., rCBF). NIRS may be useful to assess feasibility to start rehabilitation of post-stroke patients with a disorder of consciousness.