A disorder of consciousness rather than complete locked-in may be the final stage of ALS

Abstract

AbstractThe end-stage of amyotrophic lateral sclerosis [ALS] is presumed to be a complete Locked-In Syndrome [cLIS], assuming an internally preserved consciousness that would not be accessible anymore from the outside. However, whether consciousness persists at this stage of ALS remains to be demonstrated. Shifting the perspective from cLIS (presupposed consciousness) to Cognitive Motor Dissociation (to-be-demonstrated consciousness), we attempted to demonstrate consciousness and communication with two cLIS-ALS patients using a multimodal awareness assessment battery. It involved complete neurophysiological assessments, passive and active auditory oddball paradigm (Subject-Own-Name/P300), an auditory-based Brain-Computer-Interface [BCI] and activation-task imaging using functional MRI or [15O]H2O PET. Wakefulness (long-term EEG), brain morphology (CT or MRI scans) and resting brain metabolism ([18F]fluoro-deoxy-glucose PET) were used to describe the underlying cLIS brain function.While Patient 1 could initially follow simple commands, he failed twice to control the BCI. At follow-up, he showed no more evidence of command following and his oddball (Own Name - P300) cognitive responses has disappeared. At his unique evaluation, Patient 2 was neither able to follow simple commands nor to control the BCI.Both patients had altered wakefulness, brain atrophy, and a global cortico-sub-cortical hypometabolism pattern compatible with a disorder of consciousness, regarded as an extreme form of an ALS-associated fronto-temporal dementia.While it is not possible to firmly demonstrate the absence of awareness, each independent measure concurred with suggesting that a “degenerative disorder of consciousness” rather than a cLIS might be the final stage of ALS. In future cases, this dramatic cognitive decline should be anticipated before communication disappears to enable precise advance directives regarding end-of-life issues in case complete – and neurophysiologically confirmed – unresponsiveness occurs.Altogether, the neuroimaging features distinguishing the mechanisms in this rare condition is a significant milestone to understand end-stage ALS. The present clinical study calls for further exploration of this terminal stage to determine the prevalence of this profile in whom communication seems hopeless.