[A case of Moebius syndrome--electrophysiological studies of facial nerve and brainstem]

Abstract

A five-year old boy was the product of a 40 week pregnancy by vertex presentation complicated only by threatened abortion at approximately 8 weeks gestation. Apgar score was 5 after one minute. At birth he was noted to have a generalized hypotonia associated with facial diplegia, small mandible, weak suck and swallow reflexes. Admission examination revealed small mandible, mask-like facial expression and mild mental retardation. Cranial nerve examination showed bilateral blepharoptosis and facial nerve palsies. Pupil reflexes were normal, but corneal reflexes were impaired bilaterally. Diplopia due to the left abducens nerve palsy was suggested. There was no atrophy of the tongue. Motor tone, strength, and deep tendon reflexes were normal. A normal 46 XY karyotype was present. The other clinical and laboratory findings were normal. MRI of the brain was unremarkable. The characteristics of electrophysiological studies were summarized as follows: 1) Auditory brainstem evoked responses demonstrated waveforms IV-V were abnormal because their amplitudes were less than 30% of wave I bilaterally. 2) Somatosensory evoked potentials documented by central conduction times from cervical region to sensory cortex were prolonged on both sides. 3) Facial nerve conduction velocity was calculated by evoked EMGs of the mentalis muscle electrically stimulated at two distal points over the marginal mandibular branch. MCV of the left side was reduced (34.2 m/sec). 4) The amplitude of the facial muscle potentials evoked by facial nerve stimulation was reduced on both sides. 5) Blink reflex responses documented by the latency difference of R1 responses between the two sides were prolonged.(ABSTRACT TRUNCATED AT 250 WORDS)