Cortical reorganization in Bell's palsy.

PURPOSE

Bell's palsy, a unilateral, idiopathic facial nerve palsy, is a common disorder that is generally followed by a good recovery of function. The aim of this study was to investigate the impact of such a transiently decreased motor control (without deafferentation) on the functional reorganization of the brain.

METHODS

To address this issue, functional MRI was applied to 10 patients in the acute state of Bell's palsy and after their complete clinical recovery. The functional paradigm consisted of unilateral facial movements with the affected as well as the non-affected side.

RESULTS

We found an overactivity of several brain areas contralateral to the palsy that are related to error detection and sensory-motor integration in the acute stage and motor integration and control in the follow-up. Functional connectivity was disrupted in the affected cortical motor system during the acute stage of Bell's palsy compared to the follow-up. This altered connectivity was found mostly between motor areas in the hemisphere contralateral to the paretic side, whereas the interhemispherical connectivity remained largely stable.

CONCLUSION

Our results indicate that a transient peripheral deefferentation causes functional reorganization in the brain that partly persists even after an apparently complete clinical recovery.