Transition from the locked in to the completely locked-in state: A physiological analysis

A. Ramos Murguialday*, J. Hill, M. Bensch, S. Martens, S. Halder, F. Nijboer, B. Schoelkopf, N. Birbaumer, A. Gharabaghi

*Corresponding author for this work

    Research output: Contribution to journalArticleAcademicpeer-review

    113 Citations (Scopus)

    Abstract

    Objective: To clarify the physiological and behavioral boundaries between locked-in (LIS) and the completely locked-in state (CLIS) (no voluntary eye movements, no communication possible) through electrophysiological data and to secure brain–computer-interface (BCI) communication.

    Methods: Electromyography from facial muscles, external anal sphincter (EAS), electrooculography and electrocorticographic data during different psychophysiological tests were acquired to define electrophysiological differences in an amyotrophic lateral sclerosis (ALS) patient with an intracranially implanted grid of 112 electrodes for nine months while the patient passed from the LIS to the CLIS.

    Results: At the very end of the LIS there was no facial muscle activity, nor external anal sphincter but eye control. Eye movements were slow and lasted for short periods only. During CLIS event related brain potentials (ERP) to passive limb movements and auditory stimuli were recorded, vibrotactile stimulation of different body parts resulted in no ERP response.

    Conclusions: The results presented contradict the commonly accepted assumption that the EAS is the last remaining muscle under voluntary control and demonstrate complete loss of eye movements in CLIS. The eye muscle was shown to be the last muscle group under voluntary control. The findings suggest ALS as a multisystem disorder, even affecting afferent sensory pathways.

    Significance: Auditory and proprioceptive brain–computer-interface (BCI) systems are the only remaining communication channels in CLIS.

    Highlights: This represents the first documentation of transition of a patient with ALS from the Locked In State the to Completely Locked In State, and the first EMG documentation of loss of all muscle activities, including sphincter function, but with retained cognition as measured with ERPs. In this patient, any stimulation, communication or learning using visual and tactile stimuli was lost. Visual BCI was useless.The findings suggest ALS as a multisystem disorder, even affecting afferent sensory pathways.
    Original languageEnglish
    Pages (from-to)925-933
    Number of pages9
    JournalClinical neurophysiology
    Volume122
    Issue number5
    DOIs
    Publication statusPublished - May 2011

    Keywords

    • HMI-HF: Human Factors
    • Amyotrophic lateral sclerosis
    • ECoG
    • Brain-computer interface
    • Locked-in syndrome

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