Abnormalities induced in reciprocal inhibition between orbicularis oculi and levator palpebrae following peripheral facial palsy.

Abstract

Peripheral Facial palsy (PFP) is generally considered a benign condition with good recovery and no sequelae. Yet, a distortion in the gesture and abnormal blinking, as those typically found in blepharospasm, can potentially develop early on. Such abnormal movements seem to be related to remodelling mechanisms that take place in the process of recovery. We report 2 cases where such clinical features became evident following an idiopathic PFP, as a result of reciprocal inhibition of orbicularis oculi and levator palpebrae. Hence, the neurophysiological study revealed an increased frequency in the blinking, with bilateral trigeminal-facial facilitation and, most notably, a disturbance that only became evident when the eyes were maintained wide open. Interestingly, those features were not reproduced in other tasks where the blinking conditions had not been altered. Our findings suggest that sensory inputs (reflex afferent pathways) are involved in such abnormal movements. The insufficient eyelid closure (lagophthalmus) in the context of PFP is likely to account for the exaggerated corneal vulnerability, thus resulting in abnormal mechanisms of adaptation.