Brain activity in an end-stage ALS patient suggests the presence of an unresponsive wakefulness syndrome.

Abstract

Objective: Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease primarily affecting motor neurons. It is widely assumed that cortical structures beyond motor neurons are relatively preserved, and patients in the end-stage ALS are regarded as being in complete locked-in syndrome (cLIS). However, emerging evidence suggests substantial heterogeneity in cognitive functioning among ALS patients, indicating possible extra-motor cortical involvement and impaired levels of consciousness. We report a case study assessing electrophysiological markers and auditory system integrity to evaluate the presence of covert consciousness in end-stage ALS.

Methods: The patient was a 42-year-old woman with bulbar-onset, end-stage ALS, a six-year disease duration, and no means of communication. She underwent several EEG-based protocols, including resting-state EEG (RS-EEG), a passive auditory oddball paradigm, and 40 Hz auditory steady-state responses (ASSR). Audiological evaluation comprised transient-evoked and distortion-product otoacoustic emissions, as well as auditory brainstem responses (ABR).

Results: RS-EEG was dominated by prefrontal 1-3 Hz activity resembling frontal intermittent rhythmic delta activity. Power spectra were poorly differentiated and consistent with a 1/f profile. No event-related potentials were observed in the oddball paradigm, and no ASSR responses were detected. Audiological testing revealed absent otoacoustic emissions and ABR indicating severe to profound hearing loss.

Conclusions: Our findings indicate severe cortical dysfunction and provide no electrophysiological evidence of covert consciousness. The electrophysiological profile closely resembles that observed in unresponsive wakefulness syndrome. This case supports the hypothesis that advanced ALS following cLIS onset may be more appropriately conceptualized as a disorder of consciousness rather than persistent cLIS.