Objective: We aimed to analyze prepulse inhibition (PPI) of blink reflex (BR) in a group of patients with cervical dystonia (CD) to determine sensory modulation of motor system.

Background: CD is a segmental dystonia affecting the muscles of neck and sometimes shoulders. CD has now been considered as a disorder of sensorimotor gating probably causing input-output mismatch in specific motor programs. PPI is a neurophysiological method which may be defined as inhibition of a reflex response by applying a subthreshold stimulus before the principal stimulus.

Methods: A total of consecutive 20 patients with idiopathic CD and 25 age- and sex-matched control subjects were enrolled in this study. Blink reflex and PPI of BR were recorded. PPI was created by stimulating median nerve at wrist using an electrical stimulus of intensity at 2 times the threshold just 100 ms and 300 ms before the principal stimulus to the supraorbital nerve.

Results: The mean ages of patient group and healthy subjects were 39.4±8.8 and 37.3±9.4, respectively (p=0.462). There were 14 (70%) patients experiencing sensory trick and 10 (50.0%) patients were botulinum toxin naive. Baseline values of R2 latency, amplitude and area were similar between groups. Logistic regression demonstrated that presence of sensory trick was an independent factor for presence of PPI (p=0.007). Prepulse inhibitions at 100 ms and 300 ms were not significant in the patient group (p=0.420) whereas there occurred prominent inhibitions in healthy subjects (p=0.000).

Conclusions: CD is associated with decreased PPI, however, sensory trick represents preservation of PPI and an adaptive mechanism in CD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/pre-pulse-inhibition-of-blink-reflex-in-cervical-dystonia/