Electromyography (EMG) studies of 172 children with congenital facial palsy were analysed retrospectively at the Hopital d’Enfants Armand-Trousseau, Paris, France. The first clinical and EMG exams were done from 3 to 90 days after birth in 103 infants, 3 to 12 months in 49, and from 1 to 2 years in 20 children. In 85 with unilateral congenital facial paralysis without malformation, 48 were attributed to perinatal forceps or other trauma. Clinical and EMG monitoring showed slow nerve regeneration and muscular reinervation even after 2 years. Asymmetrical crying facies occurred in 51 infants, the EMG showed partial denervation of the depressor anguli oris and depressor labia inferioris, and a diagnosis of partial facial palsy with only the lower lip involved. Orofacial malformations with asymmetrical facial motility were studied in 33 infants. EMG activity was either absent (10 infants), neurogenic (9), or myopathic (14). Pseudoparalysis asymmetry of postural origin occurred in 5 of 172 cases of congenital facial palsy. The EMG was normal and the functional asymmetry resolved within 2 months. Mobius syndrome in 22 infants had heterogeneous EMG findings with predominance of axonal loss. Congenital facial diplegia with muscular diseases, eg myotonic dystrophy, congenital muscular dystrophy, metabolic myopathies, facioscapulohumeral dystrophy with early onset facial weakness. In Orofacial apraxia with cerebral palsy, EMG of facial muscles is normal, except when brain stem nuclei are involved. In 12 infants with dysphagia at birth and failure to thrive, a neurogenic EMG indicated lesions of VII to XII cranial nerves. 
COMMENT. The author advocates EMG of facial muscles in infants to differentiate causes of congenital facial palsy and to evaluate course and prognosis. Electrodiagnostic studies of Mobius syndrome may shed light on the pathophysiology. The author provides details regarding his technique of EMG and findings, and values for motor latencies of facial muscles and facial nerve conduction velocities from birth (19 m/s) to 3 years (39 m/s).