Blink reflex recovery in central and peripherally originated movement disorders of the cranio-cervical area: A comparative study
Background: Previous studies have shown that enhancement of blink reflex (BR) excitability exists in various movement disorders, notably those involving the cranio-cervical area. In this study the BR recovery curve of the late component (R2) and R2 area was evaluated to determine what changes occur under different conditions and the significance of these changes. Methods: The recovery curve of the blink reflex (BR) was studied inpatients with hemifacial spasm (HFS), post-facial syndrome (PFS), blepharospasm (BS), segmental cranio-cervical dystonia (SD), cervical dystonia without BS (CD), and healthy control subjects. Following initial comparisons between six groups where the increased excitability observed in BS, SD and CD were assumed to be of central origin and that of HFS and PFS of peripheral origin; two additional groups were established and compared in terms of recovery times. Results: Recovery values of 200, 400, 600, 800, 1000 ms and grades for all groups were significantly different when compared to the control group. The most significant difference observed between the groups was at 200 msn and the smallest at 800 msn interstimuli intervals. The subjects within the group referred to as the 'central origined group' recovered faster than those in the 'peripherally origined group' although no statistical difference was found between the two groups at stimulus interval. Conclusion: Our findings suggest that the excitability changes observed among the groups can be attributed to a number of factors. Although the nature and anatomical substrate of the primary pathology involving the reflex cycle leads - to some extent - to differently enhanced excitability patterns, such differences were not considered statistically significant.