Background Recent neuroimaging studies point to a possible pathophysiological role of cerebellar dysfunction in dystonia. The authors investigated the association between sensorimotor adaptation, cerebellar dysfunction and the myoclonus–dystonia phenotype.

Methods The authors prospectively analysed reactive saccade adaptation in a genetically homogeneous group of 14 patients with DYT11 dystonia owing to a mutation of the SGCE gene. The authors used a backward reactive saccade adaptation task, a well-characterised experimental oculomotor paradigm involving the cerebellum. The principle of this paradigm is to simulate a spatial error in saccade generation by systematically shifting a visual target during saccade execution. Repetition of this systematic error induces a gradual decrease in the initial saccade amplitude, reflecting an adaptive phenomenon.

Results Saccade adaptation was significantly lower in the DYT11 patients than in healthy controls (mean value: 8.9%±4.5% vs 21.6%±4.5%; p=8.3×10⁻⁶). The time course of adaptation also differed between the patients and controls (p=0.002), reflecting the slower saccadic adaptation in the patients.

Conclusions This study provides the first neurophysiological evidence of cerebellar dysfunction in DYT11 dystonia and supports a role of cerebellar dysfunction in the myoclonus–dystonia phenotype.