Objective: Characterize the phenomenology and natural history of adult onset idiopathic truncal dystonia.

Background: Focal dystonias are the most common type of adult-onset dystonia, however, apart from the neck, they infrequently affect axial musculature. Additionally, while truncal dystonia is often attributed to secondary etiologies such as Parkinson’s disease or neuroleptic exposure, idiopathic adult-onset truncal dystonia has only been previously described in case reports and small case series. We characterize 7 cases of adult-onset primary truncal dystonia and discuss them within the scope of the existing literature.

Methods: We conducted a retrospective chart review of medical records and patient videos for adult patients with the diagnosis of idiopathic truncal dystonia.

Results: In our group of 7 patients, the mean age of onset of truncal dystonia was 47.6 and there was a male predominance (85.7%). Truncal flexion was the most common primary direction of dystonic movement (57.1%), which was accompanied by lateral pulling in 2 patients and right anterior shoulder movements in 1 patient. The dystonic movements occurred only with action in 57.1% and occurred at rest though were worsened by action in 28.6%. Our findings were similar to those previously reported by Bhatia et al (J Neurol Neurosurg Psychiatry 1997), in which 55.6% of patients were male, mean age of onset was 41, the primary direction of axial movements was flexion (55.6%), and the dystonia was worsened by action in the majority. Somewhat similar results were also reported in a group of 4 patients by Shaikh et al (Parkinsonism and Related Disorders 2014), with mean age of onset of 55.5, 50% male, and 50% who exhibited truncal flexion as the primary direction of dystonia. Our cases were also consistent with previous reports of minimal to mild improvement with pharmacotherapy and/or botulinum toxin in the majority of patients.

Conclusions: Similar to previous reports of adult-onset truncal dystonia, our results showed that the majority of patients were male, exhibited truncal flexion as the primary direction of dystonic movements, and dystonia was action-induced or worsened by action. While identification of these common features can aid in diagnosis, the consistent findings of poor to modest response to treatments indicate a need for future studies to find more effective treatments for this rare but disabling condition.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/phenomenology-of-idiopathic-adult-onset-truncal-dystonia/