Moebius syndrome

What is Moebius syndrome?

Child with Moebius syndrome

Moebius syndrome is an extremely rare neurological disorder which is present at birth. The exact incidence is unknown. It is characterised by weakening or paralysis of the muscles in the face which control expression and lateral eye movements. People born with Moebius syndrome are unable to smile or frown, blink their eyes, or suck, although sometimes only one side is affected. Predominantly the sixth and seventh cranial nerves are involved but other nerves may also be affected. The sixth and seventh cranial nerves are pairs of nerves (one on each side of the face) which send messages from the brain and are responsible for certain facial movements and sensory functions. With Moebius syndrome, these nerves are either absent or underdeveloped, resulting normally in bilateral facial paralysis, although sometimes only one side is affected. Other physical problems are sometimes present in people with Moebius syndrome, such as clubfoot; mouth, tongue and jaw deformities; and respiratory illnesses. Although Moebius syndrome is sometimes associated with intellectual disabilities such as autism, and development delays, it mainly affects children of normal intelligence and cognitive development. The disorder is named after the German physician Paul Julius Möbius who described the condition in 1888. More recently it has been referred to as Moebius sequence, a more accurate description of this kind of disorder, where a single embryological event leads to a chain of developmental defects. Some instances of Moebius syndrome may be accompanied by Poland’s Anomaly, but this is usually infrequent.

What causes Moebius syndrome?

Child with Moebius syndrome

The cause of Moebius syndrome is unknown. Research is ongoing to try and establish environmental and/or genetic factors that may be connected to incidences of Moebius syndrome. What is clear is that the development of the cranial nerves VI and VII is somehow disrupted as the embryo grows in the womb. In more severe cases, additional cranial nerves are involved. A small percentage of cases of Moebius syndrome have been reported to run in families but there is no single clear pattern of inheritance and the majority of cases of Moebius syndrome are sporadic.

There may well be sub-groups of Moebius syndrome and these may have different causes, but this still remains a subject of research.

What are the symptoms of Moebius syndrome?

Moebius syndrome can affect people in many different ways and not everyone will have all of these symptoms. Some symptoms may also be characteristics of other neurological conditions. There is great variation in symptoms and the degree of severity. Where more cranial nerves are affected, more symptoms will arise, for example, developmental issues with the cranial nerves IX and XII may lead to impaired function of the throat and tongue.

Symptoms may include:

• Lack of facial expression, for example the inability to smile or frown.
• Absence of blinking resulting in dry and irritated eyes.
• Absence of lateral eye movement, because this movement is controlled by cranial nerve VI. (Eyes do not move from side to side, and the person turns their head instead).
• Strabismus (where the eyes are not properly aligned with each other).
• Inability to squint.
• Inability to suck: this can be an early indication when nursing an infant with Moebius syndrome.
• Difficulty in keeping the head back to swallow.
• Excessive drooling.
• The roof of the mouth may be high and arched with an abnormal opening (submucous cleft palate).
• Short or unusually shaped tongue.
• Small chin (micrognathia).
• Small mouth (microstomia).
• Missing and misaligned teeth.
• Hearing loss (where cranial nerve VIII is affected).
• Low muscle tone (hypotonia).
• Bone abnormalities in the arms, legs, hands and feet.

Problems associated with the symptoms of Moebius syndrome may include:

• Visual impairment, corneal erosion (due to inability to blink) and sensitivity to light (due to inability to squint).
• Problems with feeding, swallowing and choking.
• Speech difficulties (due to impairment of lip function, reduced tongue function, cleft palate and reduced soft palate mobility).
• Frequent ear infections (due to the function of the Eustachian tube being affected).
• Dental problems: teeth may be missing or be overcrowded due to the small size of the lower jaw. The reduction in mouth muscle movement results in less natural self-cleaning and can increase the risk of dental cavities and gum disease.
• A delay in development of motor skills, such as crawling and walking, although most children with Moebius syndrome do catch up.
• Psychological problems, particularly as the lack of facial expression can sometimes incorrectly be assumed by others to be due to unfriendliness or lack of intelligence.

How is Moebius syndrome diagnosed?

There is currently no test for Moebius syndrome and diagnosis is based on assessment of the physical symptoms and taking into account the medical history of the individual. Further examinations such as CAT scan or MRI of the brain and brainstem may be carried out in order to confirm the diagnosis. The first indication that an infant has Moebius syndrome may be a mask-like expression when crying.

Is there any treatment for Moebius syndrome?

There is no cure for Moebius syndrome but some of the symptoms can be treated.

• Infants may struggle to feed due to being unable to suck, in this case special feeding tubes or bottles may be used to ensure sufficient nutrition is received.
• Physical, occupational and speech therapy can help to improve motor skills and coordination, and address speaking and eating difficulties.
• Eye care is very important; see our dry eye patient guide for more information about this subject. Surgeries such as eyelid loading are available which can help with eye closure. Sunglasses and wide-brimmed sunhats can help children with Moebius syndrome. Being unable to squint, their eyes are extremely sensitive to the light.
• Cleft palate is usually subject to early surgical intervention (before 12 years of age). Regular check-ups with a dedicated cleft team are recommended when a child has a cleft palate.
• Surgery can be performed which if successful can provide the ability to smile, but there will still be the absence of other facial expressions, such as the ability to frown.

How do people with Moebius syndrome communicate in the absence of facial expression?

Facial expression is important in social interaction; we subconsciously express a range of emotions on our faces helping us to communicate with others. With an inability to smile, frown, look surprised and more, it may seem like a person with Moebius syndrome is disinterested or unfriendly on first meeting them. However, friends and family quickly learn to easily pick up on the emotional cues of a person with Moebius syndrome. People with Moebius syndrome can use alternative ways to communicate emotion such as body language, posture and their tone of voice.