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.
Jamal et al. (1988) described two patients (a brother and a sister) with Moebius syndrome. In addition to bilateral congenital facial nerve paralysis, both had deafness, an external deformity of the auricles, and a latent squint. The deafness in both cases was sensorineural in type; although there was paralysis of the motor part of the facial nerve, taste and lacrimation were intact.
Farag et al. (1993) conducted a clinicogenetic assessment of 400 institutionalized mentally retarded (IQ less than 50) Kuwaiti patients during a 4-year period (1986-1990). One of the patients was found to be suffering from Moebius syndrome.
Singh et al. (1992) described the first reported incidences of patients affected by Mobius syndrome along with basal ganglia calcification. The proband was a girl born at 37 weeks of gestation. Her Apgar scores were 5, 8 and 10 at 1, 5 and 10 min. Her birth weight was 1.7 kg, length was 44 cm and head circumference was 32 cm. She suffered from pronated forearms with fixed flexion deformities of the wrist and bilateral tallipes equinovarus. At 3 years of age, she showed evidence of bilateral 6th and 7th nerve palsies and a CT scan of the brain found bilateral basal ganglia and thalamic calcification. The proband’s brother, a two year old boy, was also affected. His Apgar scores were 6 and 9 at 1 and 5 min and his birth weight was 2.6 kg. He suffered from Ebstein’s anomaly and skeletal deformities similar to his sister. He also showed bilateral 6th and 7th nerve palsies as well as bilateral basal ganglia calcification. The parents of the two affected patients were first cousins. The authors noted that they had five other unaffected children as well as two children that died during the neonatal period and one miscarriage.