Direct Current Stimulation of Primary Motor Cortex and Cerebellum and Botulinum Toxin a Injections in a Person With Cervical Dystonia

Cervical dystonia is a neurological movement disorder characterized by abnormal movements and postures of the neck [ ]. Standard practice treatment is botulinum toxin A injections repeated every 3 months. While this treatment is effective the benefits commonly do not last the entire treatment cycle [ , ]. Direct current stimulation (DCS) is a form of non-invasive brain stimulation that can influence excitability of the cerebellum and primary motor cortex (M1), both implicated in the pathophysiology of cervical dystonia [ ]. It is possible that DCS to cerebellum and M1 might augment the effect of botulinum toxin injections. This idea was tested for proof of concept in a single case of a 47 year old female musician with a 14 year history of cervical dystonia. The participant had been forced into retirement from her professional career as a bassoonist in 2003 by dystonia. Her primary neck torsion at the time of the study was left rotation. Botulinum toxin injection history included 3 monthly treatments over 14 years, apart from a three year remission between 2007 and 2010. The study was approved by the local ethics committee. The participant was enrolled just prior to her usual botulinum toxin injection appointment with her neurologist. Before the appointment she underwent baseline assessments of cortical neurophysiology using transcranial magnetic stimulation (TMS) and quality of life by the self-reported Cervical Dystonia Questionnaire (CDQ-24) [ ] and Cervical Dystonia Impact Profile (CDIP-58) [ ]. Dystonia severity was assessed by the consulting neurologist using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) [ ] at the time of the injections (left splenius capitus (50 units), left levator scapulae (2 × 50 units), left upper trapezius (62.5 units) and right sternocleideomastoid (2 × 50 units)). Beginning one week after the injections, the participant attended the laboratory of an investigator (LB) for DCS twice per week until the next botulinum toxin injection appointment 12 weeks later. Outcome measures were repeated at 4, 8 and 12 weeks after the injections, apart from the TWSTRS which was assessed by the same neurologist during the second botulinum toxin injection appointment of the study period.