Alteration of interoceptive sensitivity: expanding the spectrum of behavioural disorders in amyotrophic lateral sclerosis

Background Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder with progressive loss of upper and lower motor neurons. Non-motor-symptoms, such as cognitive, emotional, autonomic, and somatosensory alterations, have been also described. Interoception represents the link between the body and brain, since it refers to the ability to consciously perceive the physical condition of the inner body, including one's heartbeat (i.e., interoceptive sensitivity, IS). Objectives To evaluate IS in ALS patients by means of a well-established task: the heartbeat perception task. Moreover, we evaluated possible correlations between IS and neuropsychological, affective, and disease-related characteristics. Methods Fifty-five ALS patients (mean-age = 60.3 +/- 12.5 years; mean disease-duration = 20.9 +/- 18.8 months) and 41 caregivers (CG) underwent the heartbeat perception task and an extensive evaluation of motor, cognitive, body awareness, affective, and emotion domains. Results ALS patients showed lower IS than CG (0.68 +/- 0.24 vs 0.82 +/- 0.16; p = 0.003). Significant correlations were found between IS and self-reported measures of alexithymia (subscale of Toronto Alexithymia scale-20 "difficulties in describing feelings"; rho = - .391, p = .003) and interoceptive awareness (subscale of Multidimensional assessment of interoceptive awareness "not worrying about pain"; rho = .405, p = .002). No significant differences were found on questionnaires for depression and anxiety between patients with ALS and their caregivers (p > .05). Conclusions ALS patients show reduced interoceptive sensitivity that is associated with poorer ability to describe feelings and with lower focalization on pain, regardless of cognitive and motor impairment. Alteration of interoception may represent a specific behavioural sign within the spectrum of emotion processing deficits described in ALS patients.