The effect of a single botulinum toxin treatment on somatosensory processing in idiopathic isolated cervical dystonia: an observational study

Joke De Pauw, Patrick Cras, Steven Truijen, Rudy Mercelis, Sarah Michiels, Wim Saeys, Luc Vereeck, Ann Hallemans, Willem De Hertogh

Patients with idiopathic cervical dystonia (CD) experience involuntary neck muscle contractions, abnormal head position and pain accompanied by dysfunctions in somatosensory processes such as postural control, cervical sensorimotor and perception of visual verticality. First-line treatment is injection with botulinum toxin (BoNT). It remains unclear whether this affects sensorimotor processes. To investigate the effect of first-line care on deficiencies in somatosensory processes. In this observational study, 24 adult patients with idiopathic CD were assessed three times over a treatment period of 12 weeks following a single treatment with BoNT. Disease severity was assessed by a disease-specific questionnaire, rating scale and the visual analogue scale. Seated postural control was assessed with posturography, cervical sensorimotor control was assessed by the joint repositioning error with an eight-camera infrared motion analysis system during a head repositioning accuracy test and perception of visual verticality was assessed with the subjective visual vertical test. Disease symptoms significantly improved following BoNT injections and deteriorated again at 12 weeks. This improvement was not accompanied by improved postural control, cervical sensorimotor control and perception of visual verticality. A trend toward improvement was seen; however, it did not reach the level of the control population. The peripheral and central treatment effects of BoNT have little to no effect on postural and cervical sensorimotor control in CD. Further research may explore whether sensory training or specialized exercise therapy improves somatosensory integration and everyday functioning in patients with CD.