Magnetic resonance (MR) findings in a 12-month-old boy with congenital unilateral facial palsy and a 9-month-old girl with atypical Moebius syndrome are reported from the National Center of Neurology and Psychiatry, Kodaira, Japan. In the boy with unilateral palsy, MRI showed an asymmetry of internal auditory channels with absence of the right facial nerve. MRI on the girl with Moebius syndrome showed a slightly hypoplastic brainstem and lack of visualization of the proximal part of the facial nerves. 3D-constructive interference in steady state (3D-CISS) MRI sequences, with reconstructions perpendicular to the bilateral internal auditory channel, were required to demonstrate facial nerve anomalies. 
COMMENT. Three-dimensional constructive interference in steady state MRI sequence is useful in the differential diagnosis of congenital facial palsy. 3D-CISS MRI provides T2-weighted images with high spatial resolution.