Abstract Background Myoclonus‐dystonia (M‐D) is a monogenic movement disorder, with proposed cerebellar dysfunction. Vergence eye movement deficits, characteristics of degenerative cerebellar disease, have not been studied in M‐D. Cerebellar transcranial alternating current stimulation (tACS) is considered a potential therapeutic approach. Objectives To assess vergence and prosaccade performance as markers of cerebellar dysfunction in M‐D and to evaluate the effects of cerebellar 50 Hz tACS on these eye movements. Methods Vergence and prosaccade performance were examined in 14 M‐D patients carrying pathogenic SGCE variants and 14 healthy controls. A subgroup ( n = 7) received real and sham 50 Hz cerebellar tACS in a randomized, double‐blind design. Results M‐D patients showed prolonged latency and reduced gain of convergence compared to controls. Divergence did not differ between groups. Prosaccade peak velocity was reduced in M‐D patients. 50 Hz cerebellar tACS showed no effect on eye movements. Conclusion Impaired convergence supports cerebellar involvement in M‐D. Further studies should identify affected pathways.
Gerkensmeier et al. (Mon,) studied this question.