Hypertrophy and asymmetry of the facial muscles: a previously unrecognized association.

We present 6 patients who do not satisfy the criteria for inclusion into any known diagnostic group, although they share similar physical findings. All had facial findings suggestive of either mild deformational plagiocephaly or craniofacial microsomia; however, hypertrophic and occasionally hyperactive muscles of the face appear to be the unifying and distinctive feature of the group. Contraction of hypertrophic postauricular muscles on the affected side resulted in movement and contraction of the pinna. Hypertrophy of the mentalis and masseter muscles was also frequently observed. Additionally, anomalous neck musculature was seen in 4 of the 6 patients. In 2 patients, the hypertrophy of certain of these muscles produced enough deformity to warrant excision. This is the first report of such an association in the literature. Possible explanations are discussed.