Revisiting Coactivation ("Froment's Maneuver") in Parkinson's Disease: A Physiological Approach.

BACKGROUND

In the 1920s, Jules Froment extensively studied conditions that might exacerbate rigidity in persons with Parkinson's disease (PD).

OBJECTIVE

This cross-sectional, controlled study aimed at investigating the physiological basis, in particular motor cortical contribution to enhanced rigidity during contralateral extremity movements.

METHODS

Motor-evoked potentials (MEPs) were recorded in 42 patients with PD and 42 age-matched healthy control subjects. Resting and active motor thresholds, MEP latency and amplitude, contralateral (cCSP) and ipsilateral cortical silent period (iCSP), and transcallosal conduction time (TCT) were obtained without and during coactivation maneuver in the dopaminergic on state.

RESULTS

At baseline, MEP amplitudes, iCSP duration, and TCT were increased in patients with PD as compared with control subjects. During coactivation, motor thresholds and TCT increased, whereas cCSP showed a marked decrease in patients with PD.

CONCLUSIONS

The reduction of cCSP during coactivation points to a disinhibition of pyramidal output. Pyramidal disinhibition may most likely underlie the enhancement of rigidity during coactivation. © 2025 International Parkinson and Movement Disorder Society.