Delta-alpha ratio correlates with level of recovery after neurorehabilitation in patients with acquired brain injury

Human Neuropsychology Laboratory, School of Psychology, Department of Experimental Psychology, C/Camilo José Cela s/n, University of Seville, Seville-41018, Andalucia, Spain.
Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology (Impact Factor: 3.1). 05/2009; 120(6):1039-45. DOI: 10.1016/j.clinph.2009.01.021
Source: PubMed


To explore the relationship between three QEEG global indexes and their association with functional outcome after neurorehabilitation in non-acute acquired brain injury (ABI) patients (traumatic brain injury and stroke).
Twenty-one adult ABI patients in post-acute phase were studied. Delta-alpha ratio (DAR), Power Ratio Index (PRI) and Mean Brain Symmetry Index (mBSI) were calculated from resting-state EEG taken at admission. These indexes and other clinical variables were correlated with functional recovery achieved after six months of neurorehabilitation.
DAR showed the highest strength of association with the functional outcome measure (rho=-0.65, P=0.002). The other QEEG indexes and clinical variables showed modest non-significant correlations. A posteriori group analysis showed higher DAR in patients with poor recovery as compared to good recovery patients.
Functional recovery after neurorehabilitation appears to be associated with a number of clinical and neurophysiological variables. Among the latter, the ratio between delta and alpha may play a significant role in predicting and monitoring functional rehabilitation outcome.
Neurophysiological assessment of ABI patients may be an important tool in monitoring and predicting outcomes after neurorehabilitation.

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    • "Alpha-to-delta ratio: The alpha-to-delta ratio (ADR) [13,18-20] was calculated as the power ratio between the alpha (8 to 13 Hz) and delta frequency band (0.5 to 4 Hz). To calculate this power ratio, a power spectral density was estimated by using Welch’s averaged periodogram method by using a Hamming window with a length of 2 seconds, resulting in a spectral-density estimation with a resolution of 0.5 Hz. "
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    • "Details on the exact EEG analysis procedure are given elsewhere [5] [23]. "
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    • "Research on the resting EEG has found lower magnitudes with higher frequencies for patients in MC compared to patients with severe neurocognitive but intact consciousness. Similarly the delta-alpha ratio correlates with the level of recovery after neurorehabilitation (Leon-Carrion et al., 2009). As the alpha rhythm (8-12 Hz) is considered to be strongly related to attention and alertness, differential responses in the alpha range to deviant stimuli can be expected. "
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