Test-Retest Reliability of ERP and Auditory Steady State Response in Patients With Disorders of Consciousness

To identify the optimal auditory evoked strategy for assessing the level of consciousness in patients with disorders of consciousness (DoC) based on event related potentials (ERP) and amplitude modulation auditory steady state response (ASSR) and its test-retest reliability, this study conducted calling names and pure tone ERP evocations, as well as amplitude-modulated ASSR evocations with 440 Hz, 1000 Hz, and 2000 Hz carrier frequencies, in recruited prolonged DoC patients. The results showed that the MMN amplitude (P<0.05) and P300 (P<0.001) of calling names was higher than that of pure tones, while the P300 latency (P<0.05) was shorter. Compared to 1000 Hz and 2000 Hz, the ASSR of 440 Hz carrier frequency exhibited more pronounced early ERSP components (P=0.001), late ERSP components (P=0.011), early ITPC components (P=0.005), and late ITPC components (P=0.008). Significant differences were observed between minimally conscious state (MCS) and vegetative state (VS) patients in P300 amplitude, MMN amplitude, P300 latency, early ERSP component, late ERSP component, and early ITPC component. P300 amplitude (MCS: ICC=0.783; VS: ICC=0.750) and early ERSP component (MCS: ICC=0.780; VS: 0.759) had excellent test-retest reliability. Correlation analysis with the CRS-R scale indicated significant positive correlations between CRS-R scores and P300 amplitude (MCS: r=0.74; VS: r=0.60), early ERSP component (MCS: r=0.72; VS: r=0.52), and early ITPC component (MCS: r=0.71; VS: r=0.49) in both MCS and VS patients. The P300 amplitude and the early ERSP component of ASSR are reliable indicators that may complement each other in assessing the patients’ level of consciousness.