Moebius syndrome (MBS) is a rare neurological condition present at birth. About 300 cases of MBS have been reported in the literature to date. It is primarily caused by the absence or underdevelopment of the 6th and 7th cranial nerves that control eye movements and facial expression, leaving the affected patients unable to move their faces; they cannot smile, frown, suck, grimace or blink their eyes, and are unable to move their eyes laterally. Many of the other cranial nerves may also be affected, including the 3rd, 5th, 8th, 9th, 11th, and 12th. Patients affected with MBS may have skeletal involvement, causing hand/feet anomalies and/or club feet. Also many problems may present such as: respiratory problems, speech and swallowing disorders, visual impairments, sensory integration dysfunction, sleep disorders, and weak upper body strength. Based on pathologic differences in Mobius syndrome patients, there are four recognized categories: Group I, characterized by small or absent brain stem nuclei that control the cranial nerves; group II, characterized by loss and degeneration of neurons in the facial peripheral nerve; group III, characterized by loss and degeneration of neurons and other brain cells, microscopic areas of damage, and hardened tissue in the brainstem nuclei; and group IV, characterized by muscular symptoms in spite of a lack of lesions in the cranial nerve. There is no treatment available for Moebius syndrome, with medical care being supportive and symptomatic.
The genetic etiology of Moebius syndrome is still unknown. This disorder is probably caused by environmental and genetic factors. In some studies, changes within regions of chromosomes 3, 10, or 13 in some families were observed in individuals affected with Moebius syndrome.