Orthostatic tremor: a cerebellar pathology?

Area of Science:

• Neuroscience
• Neurology
• Neuroimaging

Background:

• Primary orthostatic tremor (POT) is a high-frequency tremor affecting the legs and trunk when standing.
• Previous research suggested potential cerebellar involvement in POT, but direct evidence was lacking.

Purpose of the Study:

• To investigate the anatomo-functional defects in the cerebellar motor pathways associated with orthostatic tremor.
• To explore the relationship between cerebellar structural and functional changes and POT characteristics.

Main Methods:

• Multimodal neuroimaging (MRI) was used to compare 17 POT patients with 17 healthy controls.
• Electromyography quantified standing duration and tremor severity.
• Repetitive transcranial magnetic stimulation (rTMS) was applied to the cerebellum in a subset of patients.

Main Results:

• POT patients showed increased grey matter volume in the cerebellar vermis and supplementary motor area, and decreased volume in the lateral cerebellum.
• Abnormally increased functional connectivity between the lateral cerebellum and supplementary motor area correlated with tremor severity and disease duration.
• rTMS treatment reduced tremor severity and normalized cerebellar-SMA connectivity.

Conclusions:

• This study provides evidence for cerebellar pathway dysfunction in orthostatic tremor.
• Findings highlight the role of cerebello-thalamo-cortical connections in POT pathophysiology.
• Non-invasive brain stimulation may offer a therapeutic approach for POT.