Möbius (also referred to as Moebius) syndrome is a complex condition in which there is absence of facial expression and the ability to look laterally (away from the nose), usually affecting both sides of the face. The exact cause of Möbius syndrome is not known, but it is thought to be related to failure to develop the blood vessels that would normally nourish the facial muscles and nerves, although many theories exist. Difficulty in lateral gaze results from paralysis of the eye muscle that is supplied by the abducens nerve (also known as cranial nerve VI). Other nerves also may be involved; these include the glossopharyngeal nerve (important in taste and soft palate sensation and movement, also known as cranial nerve IX), the vagus nerve (responsible for the gag reflex, also known as cranial nerve X), and the hypoglossal nerve (responsible for tongue movement and known as cranial nerve XII). The manifestations of Möbius syndrome can be many and variable, depending on the extent of involvement. Infants may have feeding difficulties resulting from swallowing difficulties, poor tongue movement, and/or poor lip movement and may require gastrostomy tube placement in severe cases. Dental hygiene can be problematic due to restricted tongue movement and mouth breathing. Absence of facial expression can have significant psychosocial implications. Facial paralysis can result in poor lower lip function, resulting in drooling, poor oral competence, and/or specific speech problems (such as “b” or “p” sounds). Speech difficulties may also result from poor tongue movement and/or velar (soft palate) dysfunction.
Children with Möbius syndrome usually have normal intelligence, but because they cannot display emotion as readily as other children, they are sometimes wrongly categorized as learning disabled. Other anomalies may coincide in patients with Möbius syndrome. Approximately 25% of people with Moebius have limb differences, such as syndactyly, brachysyndactyly, clubfoot, and other differences. Möbius syndrome is sometimes associated with Poland syndrome, a congenital difference involving the chest and hands. Möbius syndrome is rarely associated with cleft palate.