Moebius Syndrome
| RONALD M. ZUKER MD, FRCSC, FACS, FAAP |
| DIVSION OF PLASTIC SURGERY |
| THE HOSPITAL FOR SICK CHILDREN |
| PROFESSOR OF SURGERY, UNIVERSITY OF TORONTO |
| RALPH T. MANKTELOW, BA, MD, FRCSC |
| DIVISION OF PLASTIC SURGERY |
| TORONTO GENERAL HOSPITAL |
| PROFESSOR OF SURGERY, UNIVERSITY OF TORONTO |
Moebius syndrome is a complex congenital anomaly characterized by a mask-like face without facial expression. Movement of the eyes in a lateral direction is often limited as well. In fact, in 1892 it was these two combinations of lack of facial expression and lack of outward eye movement that led Professor P.J. Moebius to describe this syndrome. Since then it has become apparent that other actions of the muscles in the face can also be compromised. The effects that we see clinically are multiple. These include initial swallowing difficulties that may be severe. Later, other problems become more apparent such as the lack of smile or ability to express one's emotions, problems associated with drooling, speech difficulties and articulation disorders. The eye problems consist of strabismus and limitation of eye movements. Fortunately, corneal ulceration and other features associated with poorly functioning lids are rare. Dental concerns present early and reflect the child's inability to properly cleanse the teeth after eating as tongue movements are often restricted. Mouth breathing may also contribute to poor dental hygiene. In adult life, the eyes often become uncomfortable due to increased exposure and drying.
All of these clinical features are a reflection of the absence or reduced function of the cranial nerves. Usually both sides of the face are affected. The nerves most commonly involved are the 7th which controls facial expression and the 6th which controls lateral eye movement. The next most commonly involved nerves are the 9th and 10th, or glossopharyngeal and vagus respectively. Developmental problems with these nerves result in abnormal swallowing, impaired gag reflex and nasal speech. The next most commonly involved nerve is the 12th or hypoglossal. This nerve controls tongue mobility and its weakness can lead to difficulties with swallowing, speech and oral cleansing. Next is the 3rd or oculomotor nerve which controls medial eye movements. Fortunately the other cranial nerves are only rarely involved. These include the 4th or trochlear nerve which affects upward and outward eye movement, the 8th or auditory nerve which affects hearing and the 5th or trigeminal nerve which affects facial sensation and controls the chewing muscles of the face. Only in very rare circumstances has involvement of the 11th or accessory nerve been described, affecting the ability to shrug one's shoulders. Least likely to be involved is the 1st or olfactory nerve which affects the sense of smell. Involvement of the 2nd nerve or optic nerve affecting vision has not been described with this syndrome.
In addition to the variability of cranial nerve involvement, not all nerves are involved in a symmetrical fashion or in a complete fashion. Asymmetrical and incomplete patterns can produce a multitude of combinations. The unifying feature, however, is lack of facial expression and diminished lateral eye movements.
Cause: Although the cause remains unknown, a number of theories have been proposed. These include aplasia of the developing cranial nuclei, destruction of the cranial nuclei, abnormalities of the peripheral nervous system and lastly, a primary muscle disorder. Although most cases are sporadic, there have been some familial cases described. Further research is ongoing.
Clinical Relevance: Numerous problems may affect the child with Moebius syndrome. As a newborn, feeding problems may be so severe as to lead to failure to thrive and the need for a gastrostomy. Any squint or strabismus may be amenable by surgery at a very early age. As a preschooler, the absence of facial expression begins to become an issue. The children are often interpreted as being dull, disinterested or simply rude. This may have enormous implications for psycho-social development. Because of the lack of support normally provided to the lower lip by the facial musculature, drooling and the inability to produce bilabial sounds, such as B and P, also become significant issues. It is here that muscle transplantation can be very helpful. With proper positioning, tension and innervation, lower lip support can be provided, thus helping with drooling and bilabial speech as well as facilitating a simulated smile. Being able to smile is very helpful in allowing the child to demonstrate facial emotions even though they may not be completely spontaneous or normal.
Speech difficulties may result from hypernasality (IX and X), reduced tongue mobility (XII) and poor lip positioning (VII). To sort out these issues an experienced speech pathologist can be most helpful and often is helpful in recommending appropriate intervention.
Up to 25% of patients with Moebius syndrome have limb anomalies as well. These include mild webbing of the fingers syndactyly, brachysyndactyly, Poland's syndrome, clubfoot, and other abnormalities of the hands and feet.
Intellectual development of children with Moebius Syndrome usually fits into the normal range. However, because of their lack of facial expression, speech difficulties, drooling and unusual eye movements, they are often mistakenly categorized as mentally deficient. As there is no foundation for this characterization, it is imperative that they be integrated into the normal school system and given the opportunities of any child with normal intelligence. Only in this way, can the child reach his or her full potential.
From a surgical perspective it is possible to assist these children in several ways through muscle transplantation. Support can be provided for the lower lip resulting in improvement in speech particularly sounds such as P and B that require the lips to be placed together. Mouth closure protects the teeth and gums. Last but not least, muscle transplantation can animate the face and create a smile.
Muscle transplantation involves the removal of a segment of a muscle from the thigh with its blood supply and nerve supply. It is transplanted to the face where it is appropriately positioned, the blood supply is re-established through microvascular anastomoses and the muscle is given a new innervation by attaching the muscle's nerve to a nerve in the face. The muscle is positioned so that it will support the lower lip and facilitate mouth closure. In this way oral competence and tooth and gum protection are improved. When the muscle contracts it will lift the lower lip so that bilabial speech can be assisted. Also, and perhaps more importantly, when the muscle contracts it will elevate the corner of the mouth and upper lip and produce a smile.
It is crucial that the muscle is placed in the correct position and in the correct direction, and that it be properly secured so it does not move from this position. It is also crucial that the muscle has an intact blood supply. Accordingly, the microvascular anastomoses are extremely important. Blood vessels of diameters approximating 1mm–1.5mm are put together under the operating microscope with fine interrupted sutures. Flow must go into the muscle through the artery and then exit the muscle through the vein in order for an intact circulation to be re-established. The muscle must have a nerve supply that will power it and instruct it when to contract. In children with Moebius syndrome the nerve supply is provided through the motor branch of the nerve to the masseter, one of the biting muscles. This nerve is almost always available and normal in children with Moebius syndrome and provides an excellent motor for the muscle. As this nerve is difficult to find, experience in locating it is essential. It provides an excellent and powerful innervation for the muscle transplant. Drs. Manktelow and Zuker have used this nerve to innervate the gracilis muscle in children and adults with Moebius syndrome in over 170 cases and have had very positive results.
The technical aspects of the muscle transplant surgery can be found in some of the articles that are appended in this website. It is a technically demanding procedure with little room for error. The procedure is not standardized but rather must be customized for each individual's face. Thus, involvement of individuals with experience is important in obtaining optimal results. Each side is done separately and the surgeries should be spaced at least 2 months apart.
Access to the face is through an incision in front of the ear with a slight extension below the mandible. This is a modified 'face-lift' type of incision and heals extremely well leaving a barely visible line on the face. No other incisions on the face are required. The incision in the thigh where the muscle is harvested is on the upper inner thigh where it is minimally visible. The incision in thigh does tend to form a visible scar.
The muscle begins to function at about 8-12 weeks. At that time some relatively simple exercises are necessary to strengthen the muscle and to provide symmetry. This may also help in integrating the smile into normal social functions. Adults will benefit from exercise sessions for the transferred muscle using a mirror. Frequent mirror practice and using the new smile with familiy, friends and strangers will help to develop the ability to smile without conscious effort. Eighty percent of adults "learn" to smile without biting and sixty percent learn to smile spontaneously. It may also be helpful to have some speech therapy to assist in bilabial sound production.
The surgeons pleased with the results of this muscle transplant surgery for Moebius syndrome and would be quite prepared to speak with anyone who wishes further information.