Individual studies’ results are contradictory and inadequate, even though impaired eyeblink conditioning is frequently touted as evidence for cerebellar impairment in isolated dystonia. Therefore, for a study, researchers sought to investigate the effect of dystonia, dystonia subtype, and clinical characteristics on eyeblink conditioning using a statistical model that adjusted for the factors of age and gender.

All published studies’ original neurophysiological data (up to 2019) were shared and compared to an age- and gender-matched control group. All recordings were rescored by two raters who were not aware of the participants’ identities (6,732 trials). Following confirmation of the higher inter-rater agreement, mean conditioning per block among raters was incorporated into a mixed repetitive measures model. 

In comparison to controls, isolated dystonia (P=0.517) and its subtypes (cervical dystonia, DYT-TOR1A, DYT-THAP1, and focal hand dystonia) exhibited similar levels of eyeblink training. Tremor did not affect eyeblink conditioning levels. A wide variety of eyeblink conditioning behavior was seen in both healthy and dystonia patients and sample size estimates for future investigations are offered.

The similarity of eyeblink conditioning behavior in dystonia and controls suggests a worldwide cerebellar learning loss in isolated dystonia. However, the precise methods by which the cerebellum interacts mechanistically with other critical neuroanatomical nodes in the dystonic network are yet unknown.

Reference: movementdisorders.onlinelibrary.wiley.com/doi/10.1002/mds.28967