Lip and Jaw Tremor in Parkinson's Disease.

Background: Parkinson's disease (PD) is characterized clinically by the presence of bradykinesia, rigidity, and tremor. Although upper limb rest tremor is the most common form of tremor in PD, lip/jaw tremor is identified in a proportion of these patients.

Methods: We aimed to assess the frequency, features, and correlates of lip/jaw tremor in PD.

Results: We studied 229 consecutive patients with PD. There were 39 (17%) patients with lip/jaw tremor, 22 of them (56.4%) were males. Slight lip/jaw tremor was identified in n = 10 (25.6%), mild in n = 15 (38.5%), moderate in n = 13 (33.3%) and severe in n = 1 (2.6%) case. Patients with lip/jaw tremor had a positive association with older age, greater limb rest tremor scores (P = 0.009), and higher total MDS-UPDRS-III scores (P < 0.001) in the multivariate regression analysis. There were 6 patients with isolated lip/jaw tremor (i.e. without limb rest tremor). These patients were all male (P = 0.038), tended to be older (75.7 vs. 67.7 years, P = 0.078) and had greater cognitive impairment (P = 0.034) than the rest of the cohort, but there was no association with other body tremors or total motor score.

Conclusions: Lip/jaw tremor was identified in 17% of cases; it was associated with greater motor severity and limb rest tremor, suggesting shared pathophysiology with limb rest tremor. A subgroup with isolated lip/jaw tremor showed reduced cognitive performance, but no association with other body tremors.