Objective: To determine frequency of different hypokinetic and hyperkinetic movement disorders (MD) within a spectrum of frontotemporal dementia (FTD): we examined patients with behavioral and language variants of FTD and with C9orf72-associated genetic form of the disease.

Background: FTD is a heterogeneous group of neurodegenerative disorders. Main clinical manifestations of FTD include aphasia and behavioral disturbances. In addition, FTD can present with various hyperkinetic and hypokinetic MD. The most frequent genetic cause of FTD in different populations is caused by hexanucleotide repeat expansion in C9orf72 gene. The prevalence of MD in FTD has not been studied enough.

Method: We examined the occurrence of MD phenomenology in a group of patients with FTD (N=22, the mean age 65y.o., mean age of onset 61y.o.). We also assessed the MD prevalence in three subgroups: 1) behavioral variant, bvFTD (N=11, mean age 68y.o., mean age of onset 64y.o.) 2) language variant of FTD – progressive non-fluent aphasia, PNFA (N=11, mean age 62y.o., mean age of onset 57y.o.) 3) patients with C9orf72 repeat expansion (N=4: PNFA=1, bvFTD=3, mean age 67y.o., mean age of onset 63y.o.). We evaluated the prevalence of hypokinetic MD, such as parkinsonism and corticobasal syndrome, and hyperkinetic MD such as tremor and myoclonus.

Results: In the whole group of FTD, MD were observed in 59% of patients, and some of them had more than one type of MD. In total, the MD spectrum was presented by tremor (27%), parkinsonism (22%), CBS (18%), and myoclonus (14%). In the subgroup of bvFTD the occurrence of MD was 82%, among them tremor was found in 36% of cases, parkinsonism in 36%, CBS in 36%, and myoclonus in 9%. In PNFA subgroup the occurrence of MD was 27%, among them tremor was found in 18%, myoclonus in 9% and parkinsonism in 9%. The occurrence of MD in the subgroup of C9orf72-associated FTD was 75%, among them tremor was seen in 50%, myoclonus in 50% and parkinsonism in 50%.

Conclusion: Different types of hyper- and hypokinetic MD could accompany FTD quite often. We found more frequent occurrence of MD in patients with bvFTD compared to PNFA. This difference may be related with different molecular pathogenesis of the forms under study, as well as with more vulnerable afferents from frontal cortex to subcortical gray matter in patients with bvFTD. We also found high frequent of MD in patients with C9orf72-associated FTD. The study was supported by RFBR #19-015-00533

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MDS Abstracts - https://www.mdsabstracts.org/abstract/movement-disorders-spectrum-in-patients-with-frontotemporal-dementia/