Reduced cortical plasticity and GABAergic modulation in essential tremor.

Area of Science:

• Neuroscience
• Movement Disorders
• Neurophysiology

Background:

• Essential tremor (ET) is a common adult movement disorder.
• While cerebellar dysfunction is implicated, cerebral cortex involvement is increasingly suggested.
• Motor cortex contribution to ET pathogenesis requires further investigation.

Purpose of the Study:

• To investigate the motor cortical contribution to Essential Tremor (ET).
• To assess the effects of continuous theta-burst stimulation (cTBS) on motor cortical excitability in ET patients.
• To explore potential alterations in intracortical inhibition and plasticity in ET.

Main Methods:

• Applied cTBS to primary motor and premotor cortex in ET patients and healthy controls.
• Measured motor-evoked potential amplitude, cortical silent period, and short-interval intracortical inhibition.
• Compared changes in these parameters before and after cTBS application.

Main Results:

• cTBS suppressed motor cortical excitability in ET patients, but effects were significantly shorter-lasting than in controls.
• Changes in intracortical inhibition after cTBS were reduced or absent in ET patients.
• Tremor amplitude decreased post-cTBS, while tremor frequency remained unchanged.

Conclusions:

• Inhibitory circuits in the motor cortex appear aberrant and less modifiable in ET patients.
• Reduced plasticity in response to cTBS supports abnormal gamma-aminobutyric acid (GABA) modulation in ET.
• Findings highlight the role of motor cortex dysfunction in Essential Tremor.