Background. Cervical dystonia (CD) is a neurological movement disorder characterized by involuntary contractions of the cervical musculature and is known to be associated with proprioceptive dysfunction in dystonic/nondystonic limbs. Objectives. We examined how neck botulinum neurotoxin (BoNT) injection affects wrist proprioception and the corresponding sensorimotor cortical activity in CD. Method. Wrist position sense acuity of the dominant (right) hand was evaluated in 15 CD and 15 control participants. Acuity measures were a psychophysical position sense discrimination threshold (DT; based on passive joint displacement) and joint position matching error (based on active movement). Cortical activity during the motor preparation period of the active joint position matching was examined using electroencephalography. Results. In their symptomatic state, patients demonstrated a significantly higher wrist proprioceptive DT, indicating an abnormal passive wrist position sense. Yet BoNT injections had no significant effect on this threshold. During active joint position matching, errors were significantly larger in patients, but this difference vanished after the administration of BoNT. Motor preparation of active wrist position matching was associated with a significantly higher rise of β-band (13-30 Hz) power over contralateral somatosensory-motor cortical areas in patients. This excessive cortical activity significantly declined post-BoNT. Conclusion. Wrist proprioceptive perception during passive/active movements is abnormal in CD. An excessive rise of premotor/motor cortical β-oscillations during motor planning is associated with this proprioceptive dysfunction. Neck BoNT injections normalized the cortical processing of proprioceptive information from nonsymptomatic limbs, indicating that local injections may affect the central mechanisms of proprioceptive function in CD.
Bibliographical noteFunding Information:
We greatly appreciate Dr Dennis Dykstra, Associate Professor of Rehabilitation Medicine, University of Minnesota, Mrs. Tanya Baxter from M Health Fairview Clinics and Surgery Center, University of Minnesota, and Dr Joshua Aman, Assistant Professor of Neurology, University of Minnesota, for their invaluable support in recruiting the study participants. We sincerely thank all attendees who kindly and generously dedicated their time to this research. We also extend our gratitude toward the Center for Applied and Translational Sensory Sciences (CATSS) for providing the recording facilities. The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research was partially funded by the Center for Applied and Translational Sensory Science at the University of Minnesota via a graduate student grant awarded to SK.
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research was partially funded by the Center for Applied and Translational Sensory Science at the University of Minnesota via a graduate student grant awarded to SK.
© The Author(s) 2020.
- sensory integration