Masticatory force and function in patients with hemispheric brain infarction and hemiplegia

Area of Science:

• Neuroscience
• Neurology
• Motor Control

Background:

• Animal studies suggest bilateral hemispheric control of masticatory muscles, differing from limb motor control.
• Understanding hemispheric dominance in mastication is crucial for stroke rehabilitation and neurological studies.

Purpose of the Study:

• To investigate if unilateral cortical brain infarction causes differential impairments in masticatory versus upper limb motor performance.
• To provide clinical evidence for the bilateral hemispheric control of masticatory function in humans.

Main Methods:

• Studied 16 hemiparetic patients with middle cerebral artery infarction using interviews, clinical exams, and bite-force measurements.
• Assessed upper limb function via grip-force measurements and clinical examination.
• Confirmed infarction localization using CT and MRI; assessed stroke severity with the Scandinavian Stroke Scale.

Main Results:

• All patients exhibited severe unilateral cortical infarction and marked upper limb dysfunction on the contralateral side.
• No significant temporomandibular disorders were observed.
• Masticatory muscles contracted symmetrically, and bite forces were equal between healthy and affected sides in all patients.

Conclusions:

• Unilateral brain infarction in hemiparetic patients leads to distinct motor deficits in upper limb versus masticatory muscles.
• Findings clinically support the hypothesis that both brain hemispheres are essential for controlling masticatory function and movements.