Facial muscle contraction in response to mechanical stretch after severe facial nerve injury: Clapham’s sign

Introduction: Following the onset of facial palsy, physiotherapists routinely inspect the inside of the patient’s mouth and cheek for complications such as ulceration or trauma. In several patients with complete facial nerve palsy, it was noticed that when the cheek was stretched there was subsequent spasm of the muscles of facial expression. This also occurred in patients whose facial nerve had been transected.
Case reports: We present four patients in whom this response was demonstrated. We consider the mechanism of this response and its relevance in the management of patients with facial paralysis.
Conclusion: Following severe or complete denervation, contraction of the facial muscles following mechanical stretch provides evidence of preservation of activity in the facial muscle’s excitation-contraction apparatus. Further research will investigate the clinical significance of this sign and whether it can be used as an early predicator of the development of synkinesis, as well as its relevance to facial nerve grafting and repair.