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Mouth Motor Overflow in Parkinson's Disease
Karim Makhoul1, Joseph Jankovic1
1Parkinson's Disease Center and Movement Disorders Clinic, Department of Neurology, Baylor College of Medicine, Houston, Texas, USA.
Movement Disorders Clinical Practice
|February 2, 2026
Summary
Motor overflow, or involuntary muscle movements, was observed in the faces of 32% of Parkinson's disease (PD) patients during limb movement assessments. This orofacial motor overflow phenomenon was previously uncharacterized in these muscles.
Area of Science:
- Neurology
- Movement Disorders
Background:
- Motor overflow, also known as mirror movements, is documented in neurodegenerative diseases, typically affecting limbs.
- This phenomenon has not been previously studied in facial or jaw muscles.
Purpose of the Study:
- To characterize the motor overflow phenomenon in orofacial muscles.
- To investigate the presence of involuntary facial or mouth movements during limb activation in Parkinson's disease patients.
Main Methods:
- Video recordings of Parkinson's disease (PD) patients undergoing standard OFF and ON deep brain stimulation assessments were reviewed.
- Patients were evaluated for involuntary movements in the face or mouth during rapid sequential limb movements (RSM).
Main Results:
- 32% of evaluated Parkinson's disease patients exhibited mouth motor overflow movements.
- These involuntary movements were observed upon activation by rapid sequential limb movements.
Conclusions:
- A significant portion of Parkinson's disease patients (one-third) display mouth motor overflow.
- This study systematically identifies and characterizes orofacial motor overflow in PD, highlighting a previously undocumented manifestation.
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