Spinal direct current stimulation (tsDCS) in hereditary spastic paraplegias (HSP): A sham-controlled crossover study

Objective: Hereditary spastic paraplegia (HSP) represents a heterogeneous group of neurodegenerative diseases characterized by progressive spasticity and lower limb weakness. We assessed the effects of transcutaneous spinal direct current stimulation (tsDCS) in HSP. Design: A double-blind, randomized, crossover and sham-controlled study. Setting: Fondazione IRCCS Cà Granda, Ospedale Maggiore Policlinico, Milan. Participants: eleven patients with HSP (six men, mean age ± SD: 37.3 ± 8.1 years), eight affected by spastin/SPG4,1 by atlastin1/SPG3a, 1 by paraplegin/SPG7 and 1 by ZFYVE26/SPG15. Interventions: tsDCS (anodal or sham, 2.0 mA, 20’, five days) delivered over the thoracic spinal cord (T10-T12). Outcome measures: Motor-evoked potentials (MEPs), the H-reflex (Hr), F-waves, the Ashworth scale for clinical spasticity, the Five Minutes Walking test and the Spastic Paraplegia Rating Scale (SPRS) were assessed. Patients were evaluated before tsDCS (T₀), at the end of the stimulation (T₁), after one week (T₂), one month (T₃) and two months (T₄). Results: The score of the Ashworth scale improved in the anodal compared with sham group, up to two months following the end of stimulation (T₁, P =.0137; T₄, P =.0244), whereas the Five Minutes Walking test and SPRS did not differ between the two groups. Among neurophysiological measures, both anodal and sham tsDCS left Hr, F-waves and MEPs unchanged over time. Conclusions: Anodal tsDCS significantly decreases spasticity and might be a complementary strategy for the treatment of spasticity in HSP.