An infant born with Mobius syndrome died at 22 days and was found at autopsy to have more widespread involvement of brainstem and cranial nerve nuclei than usual, resulting in an “expanded Mobius syndrome,” as reported from the University of Iowa Hospital, Iowa City, IA. At emergency cesarean section, performed at 33 weeks gestation because of fetal distress and arm tremor, a 1672 gm male infant required continuing ventilatory support. At neurologic examination, the diagnosis was expanded Mobius syndrome with diffuse cranial nerve and brainstem involvement. CT and MRI revealed diffuse cerebral atrophy. Postmortem examination showed bilateral pneumonia secondary to aspiration. The brain was of normal weight and its surface appeared normal. Cranial nerve rootlets VI-XII were absent. Microscopic examination showed bilateral brain, basal ganglia, and brainstem gliosis and mineralization. Neurons in the nuclei of cranial nerves III-XI were absent. There was lesser involvement of the spinal cord, cerebral white matter, and cerebellum. No inflammatory cells or evidence of infection were evident. 
COMMENT. Mobius syndrome is a congenital disorder usually limited to a bilateral paralysis of cranial nerves VI and VII, resulting in facial diplegia and impaired abduction of the eyes in lateral gaze. Other cranial nerves, V, IX, and XII are occasionally involved also. In some cases the involvement of the brainstem nuclei, nerves and muscles is more diffuse, leading to an expanded form of the syndrome. Limb and other craniofacial malformations may occur. In the case reported above, the pathology was particularly extensive and the infant died soon after birth. The syndrome has multiple presumed causes. As in the present report, a possible prenatal vascular insuffiency or hypoxic/ischemic event involving embryonic subclavian artery branches may cause gliosis and mineralization of selected cranial nerve nuclei or a more extensive pathology. A dysgenesis of cranial nerve nuclei and hypoplasia of nerves and muscles (oromandibular limb hypogenesis) or a primary myopathy involving facial and external eye muscles are alternative theories,. The timing of the suggested embryonic insult is in the early first trimester, Abuse of benzodiazepines, chorionic villus sampling, and placental bleeding have been invoked as causes. The term Mobius sequence is sometimes preferred to syndrome, better describing a cascade of events secondary to a proposed embryonic insult. Mobius sequence is preferred by the authors of the following report.