Objective: Compare finger individuation (FI) and maximum finger strength in healthy control, patients with Parkinson’s Disease (PD) and Spinocerebellar ataxia type12 (SCA12). We also examined correlation between index of finger individuation and flexion strength of finger.

Background: Impaired individual finger movement can affect functional ability in patients with movement disorders. SCA12 is an autosomal dominant polyglutamate disorder presents with kinetic tremor, ataxic gait, and extrapyramidal symptoms. The motor control of the finger is largely unknown in patients with movement disorders.

Method: Individual motor control of fingers and maximum force were estimated in 20 PD patients, 7 SCA12 patients and 20 healthy participants by a portable device controlled through a Raspberry Pi computer. The participants were instructed to match the expected force levels (20, 40, 60, 80% of MVC) randomly appearing on the monitor multiple times by isometric flexion of single digits. Finger Individuation (FI) index was calculated according to Xu et al., 2017. The maximum force during finger flexion was estimated. Standard clinical rating scales were used to clinically quantify the motor functions in PD and SCA12.

Results: The FI index was equally impaired in PD and SCA12 patients compared to control subjects. Strength was minimally affected in both the disease groups. FI index correlated with ataxia and extrapyramidal domain scores in SCA12 patients and motor severity score of PD. There was a lack of correlation between strength and individuation in all three groups.

Conclusion: An integrity of cerebellum, basal ganglia and thalamocortical circuits are essential to maintain individual finger movements. Strength and FI are controlled through two distinct systems with minimal overlap.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/motor-control-of-finger-individuation-and-strength-in-patients-with-parkinsons-disease-and-spinocerebellar-ataxia-type-12/