Objective: To describe synchronous involuntary rhythmic jaw movements during voluntary hand movements in parkinsonian patients. We called them “mirror” jaw movements.

Background: Mirror movements (MM) refer to ipsilateral involuntary movements that appear during voluntary activity in contralateral homologous body regions. They frequently involve the distal upper limbs during repetitive or alternating finger or hand movements. Overt MM have been previously reported mainly in Parkinson’s disease (PD) and Essential tremor (ET) patients. Here, we present 14 patients with synchronous involuntary rhythmic jaw movements during voluntary hand movements in parkinsonian patients. We called them “mirror” jaw movements. We haven’t found any previous presented or published reports with such movements.

Method: From our database of Movement disorders (MD) patients (pts) seen in the MD clinic of Lamia General Hospital between 1998-2021 we recruited those who have exhibited MM at any stage of their disorder. We routinely seek the presence of MM in all pts instructing them to perform sequential unilateral voluntary motor tasks with either the right or left limb such as finger tapping, fist rotation, finger alternation, opening and closing of the hand, hand pronation-supination, and ankle flexion-extension foot taps.

Results: We found 80 pts with hand MM. In 14 of them we had recorded the presence of synchronous involuntary rhythmic jaw movements during voluntary hand movements. In 9 of them we video-recorded these jaw movements. There were 13 male pts and one female pt. Nine pts had a diagnosis of PD, 2 had drug-induced parkinsonism, 2 had ET evolving to PD and one had an atypical parkinsonian syndrome (possibly Multiple Systems Atrophy). The jaw movements were involuntary rhythmic jaw movements synchronous with the voluntary hand movements and with the same frequency with them. They were initiated and stopped synchronously with the voluntary hand movements.They were first recorded either at the early stages of the disease during the initial examination or during follow-up visits years after. Their response to antiparkinsonian drugs was not so marked as with classic mirror hand movements.

Conclusion: Involuntary rhythmic jaw movements synchronous with the voluntary hand movements (“mirror” jaw movements) in parkinsonian and ET patients are relatively rare movements in MD pts.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/mirror-jaw-movements-in-parkinsonian-patients/