Objective: This study investigated cerebellar function in patients with primary cervical dystonia (CD) and patients with presumed functional dystonia, with the intention to both clarify the underlying mechanism and to develop a potential tool to differentiate the diagnosis of primary CD from functional CD.

Background: Recent evidence from animal models, neurophysiology and functional and structural imaging point to a cerebellar contribution in the pathophysiology of cervical dystonia (CD). The interest of clinicians lies in differentiating patients with idiopathic CD from patients with functional CD whose treatment remains poorly efficacious. As eyeblink classical conditioning (EBCC), a paradigm to investigate cerebellar functioning, was demonstrated to be impaired in patients with CD, we hypothesized that cerebellar functional integrity would be preserved in patients with functional CD. This paradigm could be complementary in evaluating the differential diagnosis.

Methods: All patients presenting with CD were evaluated by 4 movement disorders specialists neurologists. Cerebellar function is probed with a classical conditioning protocol (EBCC) in which repetitive pairing of an auditory stimulus (conditioning stimulus) with an electrically-elicited (unconditional stimulus) blink reflex which becomes conditioned to the auditory stimulus. This conditioning is an associative motor learning paradigm and depends on the functional integrity of the cerebellum.

Results: Preliminary results point at a preserved conditioning in functional dystonia suggesting intact cerebellar integrity in contrast to primary idiopathic CD.

Conclusions: Given the segregation of responses in both population, EBCC could become part of the clinical investigation to differentiate idiopathic CD from functional CD.

References: Zadro, I., Brinar, V. V., Barun, B., Ozretić, D., & Habek, M. (2008). Cervical dystonia due to cerebellar stroke. Movement disorders, 23(6), 919-920. Teo, J. T. H., Van De Warrenburg, B. P. C., Schneider, S. A., Rothwell, J. C., & Bhatia, K. P. (2009). Neurophysiological evidence for cerebellar dysfunction in primary focal dystonia. Journal of Neurology, Neurosurgery & Psychiatry, 80(1), 80-83. Neychev, V. K., Fan, X., Mitev, V. I., Hess, E. J., & Jinnah, H. A. (2008). The basal ganglia and cerebellum interact in the expression of dystonic movement. Brain, 131(9), 2499-2509. Gerwig, M., Kolb, F. P., & Timmann, D. (2007). The involvement of the human cerebellum in eyeblink conditioning. The Cerebellum, 6(1), 38.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/can-cerebellar-dysfunction-help-differentiate-idiopathic-from-functional-cervical-dystonia/