3D-Ultrasonography for evaluation of facial muscles in patients with chronic facial palsy or defective healing: a pilot study

BACKGROUND: While standardized methods are established to examine the pathway from motorcortex to the peripheral nerve in patients with facial palsy, a reliable method to evaluate the facial muscles in patients with long-term palsy for therapy planning is lacking. METHODS: A 3D ultrasonographic (US) acquisition system driven by a motorized linear mover combined with conventional US probe was used to acquire 3D data sets of several facial muscles on both sides of the face in a healthy subject and seven patients with different types of unilateral degenerative facial nerve lesions. RESULTS: The US results were correlated to the duration of palsy and the electromyography results. Consistent 3D US based volumetry through bilateral comparison was feasible for parts of the frontalis muscle, orbicularis oculi muscle, depressor anguli oris muscle, depressor labii inferioris muscle, and mentalis muscle. With the exception of the frontal muscle, the facial muscles volumes were much smaller on the palsy side (minimum: 3% for the depressor labii inferior muscle) than on the healthy side in patients with severe facial nerve lesion. In contrast, the frontal muscles did not show a side difference. In the two patients with defective healing after spontaneous regeneration a decrease in muscle volume was not seen. Synkinesis and hyperkinesis was even more correlated to muscle hypertrophy on the palsy compared with the healthy side. CONCLUSION: 3D ultrasonography seems to be a promising tool for regional and quantitative evaluation of facial muscles in patients with facial palsy receiving a facial reconstructive surgery or conservative treatment.