title: Transcranial Alternating Current Stimulation in Patients with Chronic Disorder of Consciousness: A Possible Way to Cut the Diagnostic Gordian Knot?
abstract: Unresponsive wakefulness syndrome (UWS) is a chronic disorder of consciousness (DOC) characterized by a lack of awareness and purposeful motor behaviors, owing to an extensive brain connectivity impairment. Nevertheless, some UWS patients may retain residual brain connectivity patterns, which may sustain a covert awareness, namely functional locked-in syndrome (fLIS). We evaluated the possibility of bringing to light such residual neural networks using a non-invasive neurostimulation protocol. To this end, we enrolled 15 healthy individuals and 26 DOC patients (minimally conscious state-MCS- and UWS), who underwent a γ-band transcranial alternating current stimulation (tACS) over the right dorsolateral prefrontal cortex. We measured the effects of tACS on power and partial-directed coherence within local and long-range cortical networks, before and after the protocol application. tACS was able to specifically modulate large-scale cortical effective connectivity and excitability in all the MCS participants and some UWS patients, who could be, therefore, considered as suffering from fLIS. Hence, tACS could be a useful approach in supporting a DOC differential diagnosis, depending on the level of preservation of the cortical large-scale effective connectivity.
authors.affiliation: IRCCS Centro Neurolesi "Bonino-Pulejo" Messina, S.S.113, Contrada Casazza, 98124, Messina, Italy.
authors.forename: Antonino
authors.initials: A
authors.lastname: Naro
authors.affiliation: IRCCS Centro Neurolesi "Bonino-Pulejo" Messina, S.S.113, Contrada Casazza, 98124, Messina, Italy.
authors.forename: Placido
authors.initials: P
authors.lastname: Bramanti
authors.affiliation: IRCCS Centro Neurolesi "Bonino-Pulejo" Messina, S.S.113, Contrada Casazza, 98124, Messina, Italy.
authors.forename: Antonino
authors.initials: A
authors.lastname: Leo
authors.affiliation: IRCCS Centro Neurolesi "Bonino-Pulejo" Messina, S.S.113, Contrada Casazza, 98124, Messina, Italy.
authors.forename: Margherita
authors.initials: M
authors.lastname: Russo
authors.affiliation: IRCCS Centro Neurolesi "Bonino-Pulejo" Messina, S.S.113, Contrada Casazza, 98124, Messina, Italy. salbro77@tiscali.it.
authors.forename: Rocco Salvatore
authors.initials: RS
authors.lastname: Calabrò
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003243:Consciousness; D003244:Consciousness Disorders / Q000000981:diagnostic imaging* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018458:Persistent Vegetative State / Q000000981:diagnostic imaging; D065908:Transcranial Direct Current Stimulation
keywords: Coherence; Disorders of consciousness; Effective connectivity; Transcranial alternating current stimulation; γ Band oscillations