AkiyoshiMatsugi, Physiotherapist, Shijonawate Gakuen University
Submitted August 31, 2018
I read with interest the report by Benussi et al, [1] which showed that spinal cathodal and cerebellar anodal transcranial direct current stimulation (tDCS) substantially improves motor function in degenerative ataxia.
It is generally thought that cerebellar brain facilitation (CBF) is achieved by stimulating the output fiber from the dentate nucleus at 3 m/s interstimulus intervals (ISIs). [2] My colleagues and I reported that this CBF effect was absent in spinocerebellar ataxia (SCA), [3] which is consistent with the findings reported by Benussi et al. [1] in their pre-tDCS measurements; however, Benussi et al. observed cerebellar brain inhibition (CBI) at 3 m/s ISIs post-tDCS. Further study is needed into CBF and CBI during cerebellar tDCS at 3 m/s ISIs.
A previous report showed that cerebellar single-pulse transcranial magnetic stimulation facilitates the soleus H reflex in SCA, [3] which suggests that spinal-cerebellar functional connectivity is retained in SCA. It is, therefore, reasonable to speculate that post-tDCS motor function improvements in ataxia are mediated by improved spinal-cerebellar functional connectivity. However, only spinal direct current stimulation (sDCS) improves spinal function. [4] Therefore, future studies should examine whether sDCS is the only stimulation paradigm that can improve spinal function in ataxia as measured with such proxies as the H reflex.
Benussi A, Dell'Era V, Cantoni V, et al. Cerebello-spinal tDCS in ataxia: A randomized, double-blind, sham-controlled, crossover trial. Neurology Epub 2018 Aug 22.
Iwata NK, Ugawa Y. The effects of cerebellar stimulation on the motor cortical excitability in neurological disorders: a review. Cerebellum 2005;4:218-223.
Matsugi A, Kikuchi Y, Kaneko K, Seko Y, Odagaki M. Cerebellar transcranial magnetic stimulation facilitates excitability of spinal reflex, but does not affect cerebellar inhibition and facilitation in spinocerebellar ataxia. Neuroreport 2018;29:808-813.
Priori A, Ciocca M, Parazzini M, Vergari M, Ferrucci R. Transcranial cerebellar direct current stimulation and transcutaneous spinal cord direct current stimulation as innovative tools for neuroscientists. J Physiol 2014;592:3345-3369.
I read with interest the report by Benussi et al, [1] which showed that spinal cathodal and cerebellar anodal transcranial direct current stimulation (tDCS) substantially improves motor function in degenerative ataxia.
It is generally thought that cerebellar brain facilitation (CBF) is achieved by stimulating the output fiber from the dentate nucleus at 3 m/s interstimulus intervals (ISIs). [2] My colleagues and I reported that this CBF effect was absent in spinocerebellar ataxia (SCA), [3] which is consistent with the findings reported by Benussi et al. [1] in their pre-tDCS measurements; however, Benussi et al. observed cerebellar brain inhibition (CBI) at 3 m/s ISIs post-tDCS. Further study is needed into CBF and CBI during cerebellar tDCS at 3 m/s ISIs.
A previous report showed that cerebellar single-pulse transcranial magnetic stimulation facilitates the soleus H reflex in SCA, [3] which suggests that spinal-cerebellar functional connectivity is retained in SCA. It is, therefore, reasonable to speculate that post-tDCS motor function improvements in ataxia are mediated by improved spinal-cerebellar functional connectivity. However, only spinal direct current stimulation (sDCS) improves spinal function. [4] Therefore, future studies should examine whether sDCS is the only stimulation paradigm that can improve spinal function in ataxia as measured with such proxies as the H reflex.
For disclosures, please contact the editorial office at journal@neurology.org.