Objective:

To compare and classify movement disorders in patients with specific causes of rapidly progressive dementia (RPD).

Background:

Many diseases present with RPD. The broad differential presents a unique challenge for the clinician who must rapidly organize and interpret tests to provide a timely clinical diagnosis for the patient with RPD. Movement disorders are associated with several different causes of RPD; their emergence, classification, and progression may provide clues to the specific diagnosis in patients with RPD.

Design/Methods:

Patients with RPD were prospectively enrolled between February 2016 and August 2022 at two tertiary care centers. Two neurologists independently determined etiologic diagnoses. A third neurologist systematically reviewed research records to identify movement disorders (e.g., parkinsonism, tremor, ataxia, myoclonus, dystonia, etc.) and classified these when present. Associations between movement disorders and specific causes of RPD were considered using Fisher’s exact test.

Results:

154 patients met criteria for RPD (46.7% female). The median age-at-symptom onset was 66.0 years old (range: 18.3-84.7 years). Movement disorders were detected at presentation in 45/154 (29.2%) patients and in 73/154 (47.4%) patients at some point in the illness course. Gait disorders (n=40, 52.6%) were the most frequent movement disorder observed, followed by tremor (n=30, 40.5%), rigidity (n=24, 32.4%), ataxia (n=19, 25.7%) and myoclonus (n=19, 25.7%). Movement disorders were more commonly associated with prion disease (OR=3.65, 95% CI 1.27-11.93, p=0.008), and appeared on average 89 days after symptomatic onset. Detection of myoclonus (OR=6.80, 95%CI 2.0-22.54, p<0.005) was associated with higher odds of CJD, with average time from symptom onset to myoclonus of 118 days. Bradykinesia was associated with Alzheimer disease related dementias (OR=7.38, 95%CI 1.54-46.14, p=0.004).

Conclusions:

Detection and classification of movement disorders may inform etiologic diagnosis in patients with RPD.