Effects of cerebellar theta-burst stimulation on arm and neck movement kinematics in patients with focal dystonia

Abstract

Objective To investigate the cerebellar inhibitory influence on the primary motor cortex in patients with focal dystonia using a cerebellar continuous theta-burst stimulation protocol (cTBS) and to evaluate any relationship with movement abnormalities. Methods Thirteen patients with focal hand dystonia, 13 patients with cervical dystonia and 13 healthy subjects underwent two sessions: (i) cTBS over the cerebellar hemisphere (real cTBS) and (ii) cTBS over the neck muscles (sham cTBS). The effects of cerebellar cTBS were quantified as excitability changes in the contralateral primary motor cortex, as well as possible changes in arm and neck movements in patients. Results Real cerebellar cTBS reduced the excitability in the contralateral primary motor cortex in healthy subjects and in patients with cervical dystonia, though not in patients with focal hand dystonia. There was no correlation between changes in primary motor cortex excitability and arm and neck movement kinematics in patients. There were no changes in clinical scores or in kinematic measures, after either real or sham cerebellar cTBS in patients. Conclusions The reduced cerebellar inhibitory modulation of primary motor cortex excitability in focal dystonia may be related to the body areas affected by dystonia as opposed to being a widespread pathophysiological abnormality. Significance The present study yields information on the differential role played by the cerebellum in the pathophysiology of different focal dystonias.

Network localization of cervical dystonia based on causal brain lesions

“…Several studies have found normal cerebellar function or connectivity in idiopathic cervical dystonia patients, or abnormal cerebellar function only in cervical dystonia patients with tremor (Delnooz et al, 2013;Sadnicka et al, 2014;Antelmi et al, 2016;Bologna et al, 2016;Avanzino et al, 2018). Here, we found that all lesions causing cervical dystonia were connected to the cerebellum, including cases with no head tremor ( Supplementary Fig.…”

Abnormal cerebellar processing of the neck proprioceptive information drives dysfunctions in cervical dystonia

“…torticollis / laterocollis / anterocollis / retrocollis) and simple voluntary head rotation of the healthy controls, the direction and extent of the cerebellar priming of PAS effects were similar. This is in contrast with recordings in writer’s cramp patients, in whom both types of cerebellar stimulation did not influence PAS effects 13 , 33 .…”

The interindividual variability of transcranial magnetic stimulation effects: Implications for diagnostic use in movement disorders

“…In this respect, it is interesting to note that modulation of cerebellar cortex excitability, by means of cTBS and iTBS, seems to have a different effect on M1 excitability in patients with focal hand dystonia and cervical dystonia. Cerebellar cTBS can reduce M1 excitability, measured by I/O curves, in patients with cervical dystonia but not in those with focal hand dystonia (Table ) . Similarly, in cervical dystonia, cerebellar inhibition suppressed the effect of PAS while cerebellar excitation enhanced it, whereas in writer's cramp, cTBS/iTBS of the cerebellum had no effect on PAS‐induced plasticity .…”

“…Cerebellar cTBS can reduce M1 excitability, measured by I/O curves, in patients with cervical dystonia but not in those with focal hand dystonia (Table 3). 124 Similarly, in cervical dystonia, cerebellar inhibition suppressed the effect of PAS while cerebellar excitation enhanced it, 125 whereas in writer's cramp, cTBS/iTBS of the cerebellum had no effect on PASinduced plasticity. 126 Interestingly, the effect was different between PAS responders and non-responders.…”