# Novel characteristics of the temporal transition to maximum tongue pressure in Parkinson’s disease: A pilot study

## TL;DR

This pilot study found that Parkinson’s disease patients show reduced and inconsistent maximum tongue pressure due to impaired motor control, not muscle fatigue.

## Contribution

The study identifies impaired motor control as a novel cause of reduced tongue pressure in Parkinson’s disease.

## Key findings

- PD subjects showed significantly greater decreases in maximum tongue pressure compared to controls.
- PD patients had inconsistent and delayed temporal transitions in tongue pressure generation.
- Muscle fatigue was not responsible for the reduced tongue pressure in PD patients.

## Abstract

•Repeated measurements of tongue isometric force allowed assessment of the extent of muscle wasting and temporal transitions of force generation.•The decrease in maximal tongue pressure seen in Parkinson’s disease subjects was not attributable to peripheral fatigue.•The motor control needed for the repeated, identical movements associated with maximum tongue pressure generation was impaired in Parkinson’s disease subjects.

Repeated measurements of tongue isometric force allowed assessment of the extent of muscle wasting and temporal transitions of force generation.

The decrease in maximal tongue pressure seen in Parkinson’s disease subjects was not attributable to peripheral fatigue.

The motor control needed for the repeated, identical movements associated with maximum tongue pressure generation was impaired in Parkinson’s disease subjects.

The reason why maximum tongue pressure (MTP) decreases in patients with Parkinson’s disease (PD) remains unclear. Repeated measurements of isometric force and MTP may be useful for analyzing muscle wasting and force generation. The purpose of this pilot study was to evaluate the clinical characteristics and temporal transition of MTP in PD and normal control (NC) groups.

There were 18 participants in this study: 10 with PD and 8 NCs. The MTP was measured 20 times at regular intervals. The area under the curve of MTP temporal transitions, time to reach MTP, and total transition time of the tongue pressure (time to return to baseline) were compared between the groups.

MTP decreased from baseline in PD subjects. Unlike NCs, PD subjects showed diverse and inconsistent temporal transitions. The decrease in MTP and delays in time to reach MTP and time to return to baseline were significantly greater in PD subjects (p < 0.05), while there was no group difference in area under the curve values. According to repeated-measures ANOVA, MTP was not different over time between PD subjects and NCs.

In this study, muscle fatigue did not affect the decrease in MTP seen in PD subjects, or the diversity and inconsistency of the temporal transition in MTP in that group. These findings indicate that the motor control needed for the repeated, identical movements associated with MTP generation may be impaired in PD patients.