Cervical dystonia may present with a head tremor manifesting as a jerky “no-no” or “yes-yes” head oscillation. In contrast to the tonic or non-tremor-dominant presentation (nTr-CD), this tremor dominant CD (Tr-CD) has this tremulous or tremor-dominant phenotype (Tr-CD) has been proposed to characterize an “ataxic dystonia” subtype of CD. Our analysis of the longitudinal NIH-funded Dystonia Coalition data showed that Tr-CD is a distinct entity seen in older women with a longer disease duration, with milder dystonia and more severe ataxia. Our study on neurophysiology of eye movements in Tr-CD patients highlighted maladaptive cerebellar outflow, manifesting as impaired saccade adaptation.

Through this study, we sought to study clinical and imaging differences in the cerebellum in patients with tremor- and non-tremor-dominant CD with the hypothesis that the former would demonstrate greater cerebellar disability.

Based on our sample size calculations, Tr-CD patients and age- and sex-matched nTr-CD patients were recruited from the University of Cincinnati Movement disorders clinic in a 1:1 ratio (10 each). All patients underwent the following assessment: Scale for the Assessment and Rating of Ataxia (SARA), Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS), gait variability with using ProtoKinetics Zeno Walkway, and cerebellar volume analysis extracted from brain magnetic resonance imaging (MRI) using a known semi-quantitative scale. 

Tr-CD patients exhibited worse SARA scores (9 vs. 7.5, p=0.03), greater median gait variability index (131 vs. 124, p=0.03) and greater superior vermian atrophy than nTr-CD patients (p=0.01). SARA scores inversely correlated with cerebellar volume in all patients (-0.4, p=0.04).  

Head tremor at onset of CD is a distinct subtype of CD with greater cerebellar disability. Recognition of this subtype is necessary to guide patient treatment, prognosis and future clinical trial efforts.