Corticospinal inhibition and alexithymia in multiple sclerosis patients-An exploratory study

Alexithymia is a multicomponent personality construct that could occur in up to 53% of patients with multiple sclerosis (MS), with recent works proposing higher rates of alexithymia in progressive MS. Among the available models of alexithymia, some propose a deficient interhemispheric communication and an aberrant GABAergic transmission at its origin. However, no single study has addressed the underlying physiological mechanisms of alexithymia in MS. The aim of this work was to assess the relationship between GABAergic neurotransmission and alexithymia in progressive MS by means of transcranial magnetic stimulation (TMS).

Twelve patients with high alexithymia and fifteen patients with low alexithymia were included based on Toronto Alexithymia Scale (TAS). Sociodemographic, clinical and neuropsychological data were recorded. The following corticospinal excitability measures were obtained: resting motor threshold, cortical silent period (CSP which reflects cortical GABAergic function), and interhemispheric inhibition (i.e., GABAergic function mediated by interhemispheric fibers).

No significant group differences were observed regarding sociodemographic, clinical or neuropsychological variables. Patients with high alexithymia scores exhibited shorter CSP than those with low alexithymia scores (81.87 ± 45.72 ms vs. 145.27 ± 77.26 ms, respectively, p < 0.05). A significant inverse correlation was also found between TAS scores and CSP duration (r = -0.59, p < 0.05).

This study offers insights into the neurophysiological mechanisms of alexithymia in MS. Reduced GABAergic transmission, as reflected by short CSP, seems to be associated with alexithymia in this population. Future studies would benefit from a more comprehensive evaluation of cortical and interhemispheric mechanisms in MS patients with alexithymia.