Noninvasive brain stimulation in Huntington's disease

Area of Science:

• Neuroscience
• Neurology
• Pathophysiology

Background:

• Huntington's disease (HD) is a neurodegenerative disorder.
• Understanding HD pathophysiology is crucial for developing effective treatments.

Purpose of the Study:

• To investigate the excitability and plasticity of brainstem and cortical circuits in HD patients using neurophysiological techniques.
• To explore the potential of repetitive transcranial magnetic stimulation (rTMS) as a therapeutic intervention for HD.

Main Methods:

• Utilized neurophysiological techniques including blink reflex studies (paired-pulse and repetitive stimulation of the supraorbital nerve) and transcranial magnetic stimulation (TMS).
• Assessed brainstem interneuron excitability and plasticity.
• Evaluated primary motor cortex (M1) excitability, focusing on inhibitory intracortical circuits (cortical silent period, short afferent inhibition).
• Investigated M1 plasticity using repetitive TMS (rTMS) protocols.

Main Results:

• Demonstrated abnormal excitability and plasticity of brainstem interneurons.
• Reported abnormal excitability of inhibitory intracortical circuits in the M1.
• Showed altered short-term and long-term M1 plasticity.
• Found that abnormal cortical excitability and plasticity are present even in early HD stages and in asymptomatic carriers.

Conclusions:

• Neurophysiological techniques have significantly advanced the understanding of HD pathophysiology.
• Abnormalities in brainstem and cortical excitability and plasticity are key features of HD.
• These alterations are detectable early in the disease course, including in asymptomatic carriers.
• Preliminary evidence suggests rTMS may be a viable therapeutic option for improving chorea symptoms in HD.