Abstract
Cognitive motor dissociation (CMD) can improve the accuracy to predict recovery of behaviorally unresponsive patients with acute brain injury, but acquisition and analysis of task-based electroencephalography (EEG) are technically challenging. N2 sleep patterns, such as sleep spindles on EEG, have been associated with good outcomes, rely on similar thalamocortical networks as consciousness and could provide less technically challenging complementary outcome predictors. In this prospective observational cohort study of 226 acutely brain injured patients, well-formed sleep spindles (WFSS) were more likely present in those with CMD than in those without CMD, often preceding the detection of CMD. WFSS were associated with a shorter time to recovery of consciousness, and both CMD and WFSS independently predicted recovery of independence, controlling for age, admission neurological status and injury type. WFSS are seen in approximately every third behaviorally unresponsive patient after acute brain injury, frequently precede detection of CMD and are a promising complementary predictor for recovery of consciousness and functional independence.
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Data availability
The primary patient-level data that support all the main analyses are available as part of Extended Data Figs. 4 and 5, including sleep data, CMD status, sedation data and outcomes data. Other individual patient data are not openly available due to reasons of sensitivity for patient privacy reasons.
Code availability
The code to analyze EEG for cognitive motor dissociation was previously shared (see Claassen et al.26). All other codes used based on publicly available R packages are non-proprietary (R version 4.0.3, R package GLM version 4.1-2, R package survival version 3.2-7, R-package survminer version 0.4.8, R package tidycmprsk version 1.0.0 and R package riskRegression version 2023.03.22).
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Acknowledgements
We thank the nurses, attending physicians, fellows and neurology residents of the neuroscience ICU for their overall support of this project. We are grateful to the National Institutes of Health (NIH)/National Institute of Neurological Disorders and Stroke (NS106014; LM011826) and the Clinical and Translational Science Awards (UL1TR001873 from the National Center for Advancing Translational Sciences/NIH) for support of this study.
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The study was conceived and designed by J. Claassen. Data were acquired and analyzed by E.E.C., Q.S., V.K., N.C., A.M., I.N.-K., J.L., A.P., M.V., S.E., J. Carmona, L.K., Y.L.S., A.V. and J. Claassen. The paper and figures were drafted by E.E.C., Q.S., V.K. and J. Claassen. Edits to the paper were provided by C.A.S., J.K., E.S.C., S.G., S.A., D.R., S.P. and P.K.
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The authors declare no competing interests. J. Claassen is a minority shareholder at iCE Neurosystems, but this amounts to less than $10,000 and less than 5% equity in the company. No technology from iCE Neurosystems was used for any of the study procedures, data acquisition or analysis presented here. None of the patients included in this study were managed using any technology from iCE Neurosystems.
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Extended data
Extended Data Fig. 1 Consort diagram.
EEG, electroencephalography; WLST, withdrawal of list sustaining treatment.
Extended Data Fig. 3 Presence of K-complexes and Vertex waves and their relationship to sleep spindles in CMD and non-CMD patients.
Presence of K-complexes and vertex waves in the entire patient cohort (a), CMD positive patients (b), and CMD negative patients (c) was highly correlated with concomitant presence of sleep spindles.
Extended Data Fig. 4 Post-injury timeline of CMD testing and presence of sleep spindles in CMD positive patients.
Well-formed sleep spindles frequently preceded the detection of CMD.
Extended Data Fig. 5 Post-injury timeline of CMD testing and presence of sleep spindles in CMD negative patients.
Of those CMD negative patients with delayed sleep spindles, well-formed sleep spindles were still predictive of recovery of consciousness, and 12-month outcome. Similarly to CMD positive patients, when well-formed sleep spindles were present on EEG, they were likely to persist on subsequent EEG recordings.
Extended Data Fig. 6 Level of sedation at the time of EEG recording and associated presence and quality of sleep spindles (N = 530).
Patients receiving “moderate” (p = 0.0002, OR = 0.4 [0.3, 0.7]) and “minimal” or “low” levels of sedation (p < 0.0001 OR = 0.5 [0.3, 0.7]) were less likely to have well-formed sleep spindles present when compared to those with no sedation.
Extended Data Fig. 7 Time to recovery of consciousness defined by CRS-R ≥ 8 and MCS + /EMCS.
Time to CRS-R ≥ 8 is significantly shorter than time to MCS + /EMCS (p = 0.04).
Extended Data Fig. 8 Sequencing of WFSS, CMD, and CRS-R ≥ 8.
Time to detect WFSS is significantly shorter than time to detect CMD in the overall cohort (Panel a). Time to CRS-R ≥ 8 is shorter for those with CMD (Panel b) but not for those without CMD (Panel c) except for non-CMD patients with WFSS (Panel d). Amongst patients with WFSS, 35% (6 of 17) of patients with and 46% (25 of 54) of patients without CMD recovered consciousness (Panel e). Amongst patients without WFSS, 25% (4 of 16) of patients with and 21% (30 of 139) of patients without CMD recovered consciousness. Patients with CRS-R ≥ 8 are kept in orange and first detecting WFSS, CMD and CRS-R are indicated by a green diamond, blue triangle, and orange dot, respectively. CMD, cognitive motor dissociation; CRS-R, coma recovery scale-revised; well-formed sleep spindles, WFSS.
Extended Data Fig. 9 Study Timeline.
This schematic depicts the timeline of testing and results for an exemplary patient found to have well-formed sleep spindles, followed by positive CMD testing, and ultimately recovery of consciousness and long-term functional recovery.
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Carroll, E.E., Shen, Q., Kansara, V. et al. Sleep spindles as a predictor of cognitive motor dissociation and recovery of consciousness after acute brain injury. Nat Med 31, 1578–1585 (2025). https://doi.org/10.1038/s41591-025-03578-x
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DOI: https://doi.org/10.1038/s41591-025-03578-x
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