Vestibular evoked myogenic potentials are intact in cervical dystonia

Vestibular dysfunction has been reported in patients with cervical dystonia (CD), but it is still unclear whether the abnormalities occur as part of the CD syndrome or whether they arise from the abnormal posture and movement of the head. We compared vestibular-evoked myogenic potentials (VEMPs) recorded from the affected neck muscles (i.e., cervical VEMPs) with those recorded from muscles unaffected by the dystonia, the extraocular muscles (i.e., ocular VEMPs). We compared 21 patients and age-matched normal controls to investigate whether these short-latency reflexes are altered in CD. We also measured subjective visual horizontal (SVH). Seven patients had not received botulinum toxin treatment (naïve group), 10 were receiving regular injections (treatment group), and four had previously received treatment but had developed antibodies (antibody group). Both cervical and ocular VEMPs were present in the majority of patients and controls. For both reflexes, there were no significant differences between stimulation of the two sides of the head, between the treatment groups, or between the patients and controls. There was also no difference in degree of deviation of SVH between the groups. Our results showed that VEMPs can be reliably recorded from both the neck and extraocular muscles in patients with CD, even after long disease or treatment durations, and provide evidence for intact short-latency vestibular reflexes in CD.