The Role of stimulus-induced Skin Conductance in Disorder of Consciousness: A Systematic Review

Disorders of consciousness (DoC) are characterized by severe impairments in arousal or awareness and remain challenging to assess accurately with standard behavioral tools alone. Skin conductance (SC), as an index of autonomic arousal, may offer a complementary, motor-independent marker of residual responsiveness. This systematic review examined studies combining sensory stimulation paradigms with SC recordings in patients with DoC, aiming to identify which stimuli are most frequently employed and how they relate to clinical and neurophysiological outcomes. A comprehensive search of PubMed, Scopus, EBSCO, Embase, Cochrane Database, and Web of Science yielded to nine eligible studies, comprising a total of 134 patients diagnosed with coma, vegetative state/unresponsive wakefulness syndrome, or minimally conscious state. Auditory stimulation was adopted by all nine studies, with highly heterogeneous protocols encompassing verbal stimuli (e.g., own name, familiar narratives, emotionally salient words), synthetic tones, environmental sounds, and musical excerpts; three studies additionally incorporated non-auditory modalities (tactile, olfactory, or multisensory). Emotionally salient or personally relevant stimuli tended to elicit stronger SC responses than neutral stimulation, although responses in patients were often delayed, attenuated, or inconsistent compared with healthy controls. From a neurobiological perspective, reproducible SC differentiation between emotional and neutral stimuli may reflect residual engagement of limbic-autonomic and salience-related networks, rather than a simple spinal or brainstem reflex. Accordingly, SC should not be considered a standalone diagnostic marker, but a low-cost, bedside-compatible complement to behavioural scales that may help identify covert autonomic processing and guide standardized, multimodal assessment protocols, particularly those based on validated affective environmental sounds.