The causes of the Moebius syndrome are still unknown. Caring for patients with Moebius syndrome requires the cooperation of many specialists. Find out about the Moebius syndrome, how is the diagnosis and treatment of Moebius syndrome, and the prognosis of Moebius syndrome.

Moebius Syndrome (MBS, Möbius Syndrome)is a rare group of birth defects involving the nervous system. In the course of the Moebius syndrome, nerves are damaged, which are responsible, among others, for facial expressions. Patients with Moebius syndrome may coexist with other neurological and developmental disorders.

Moebius syndrome - symptoms

Moebius syndrome is one of the rare neurological diseases. Its frequency is estimated at 1 / 250,000 live births, although this number is probably underestimated. Moebius syndrome is most often diagnosed in infants and young children, but in many cases the diagnosis is delayed.

The main cause of it is the wrong attribution of Moebius syndrome symptoms to other disorders (most often a past perinatal trauma).

The essence of the Moebius syndrome is damage to two cranial nerves (numbers VI and VII), leading to their paralysis.

The human nervous system is equipped with twelve pairs of cranial nerves, marked successively with Roman numerals from I to XII. The cranial nerves are responsible for the control of movement, sensation, perception of sensory stimuli and performing the intended activities within the head and neck.

Thanks to the cranial nerves, we can move our eyeballs, make different faces, see and hear, smell and taste, as well as swallow and talk.

The basic defect in Moebius syndrome is damage to the VI and VII cranial nerves. Their names are the abduction nerve and the facial nerve, respectively. The VI (abduction) nerve is responsible for the eyeball abduction movement (the shift of the eyeball in the horizontal plane towards the outer corner of the eye). The VII (facial) nerve is responsible for our facial expressions because it allows the facial muscles to move.

Additionally, the VII nerve is involved in tearing, saliva production, taste, and the perception of sound. Paralysis of these nerves is the cause of the two main symptoms of Moebius syndrome:

  • facial expression impairment
  • and eyeball abduction disorders.

Paralysis of the facial muscles in Moebius syndrome can be observed in the early stages of a child's life. The first visible symptoms are a weakened suckling reflex and problems with swallowing food, which may result in feeding difficulties.

Lack of facial expressions gives the impression of a "masked" face - the child does not smile, frown or show grimaces. There are also numerous ophthalmological problems in the Moebius syndrome. The weakening of the circular muscles of the eyes prevents squeezing the eyelids, and the paralysis of the facial nerve disrupts the work of the lacrimal glands. For this reason, the front part of the eyeball is constantly exposed to drying out and irritation.

The inability to move the eyeballs sideways means that in order to look to the side, the child has to rotate the entire head. Paresis of the abduction nerve can also result in strabismus.

The spectrum of symptoms of Moebius syndrome is very wide. The paralysis of the facial nerves can be both unilateral and bilateral. In asymmetric variants of the syndrome, there is often only a partial paresis of the facial muscles (for example, affecting only the lower part of the face on one side).

The image of the Moebius syndrome includes a permanent defect of the VI and VII cranial nerves, but in many cases the disease is also accompanied by damage to other cranial nerves.

A defect in the VIII (auditory) nerve may cause hearing impairment or even complete deafness. Oral problems such as micrognation (underdevelopment of the mandible) and microglossia (underdevelopment of the tongue) are relatively common in Moebius Syndrome. The most common consequences are swallowing and speech problems.

Moebius syndrome - accompanying diseases

The spectrum of the Moebius syndrome symptoms is wide, and the picture of the disease may include many accompanying disorders. Disorders of facial expressions have psychological and social consequences due to difficulties in communication with the outside world. Paralysis of the facial muscles significantly hinders the expression of emotions.

For many years it was believed that autism spectrum disorders occur more frequently among people with Moebius syndrome than in the general population. Contemporary scientific research does not always confirm this theory - the diagnosis of autism spectrum disorders is often controversial due to the significant impact of physical defects on the social functioning of patients.

Moebius syndrome can be associated with a variety of birth defects. In addition to the paresis of the VI and VII facial nerves, the following can coexist in the head and neck area:

  • cleftpalate,
  • malocclusion
  • and language distortions.

Various defects of the skeletal system are found in more than half of patients with Moebius syndrome:

  • Varus feet,
  • syndactyly (fused fingers),
  • brachydactyly (shortening the fingers)
  • and underdevelopment of hands and feet.

Congenital defects of the heart and genitourinary system may coexist with Moebius syndrome.

About 6-10% of Moebius syndrome cases are accompanied by Poland's syndrome. It is a congenital disease in which the structure of the chest is disturbed as a result of underdevelopment of the pectoral muscle. The coexistence of these two diseases is called the Poland-Moebius syndrome.

Children with Moebius syndrome are at risk of developing delays in psychomotor development. The slowed down development is due to, inter alia, with:

  • emotional expression disorders,
  • speech difficulties,
  • as well as ophthalmological problems (hindering, among others, eye-hand coordination).

Babies with Moebius syndrome may later reach milestones such as crawling and walking, however around age 3 they usually "catch up" with their peers and achieve an appropriate level of motor development.

The image of the Moebius syndrome may include a slight intellectual disability, however, it affects only a few percent of patients. In the vast majority of children with Moebius syndrome, the IQ is within the normal range.

Moebius syndrome - causes

The causes of the Moebius syndrome have not yet been unambiguously known. The team is likely to be based on a combination of genetic and environmental factors.

There are many hypotheses concerning the mechanism of palsy of the cranial nerves in Moebius syndrome. The most likely of them seems to be damage to a part of the brain stem in the very early stages of fetal development.

There are still no credible explanations for the causes of numerous defects accompanying this disease (including congenital limb defects).

Moebius syndrome occurs all over the world, regardless of ethnicity, with equal frequency in both sexes. The disease most often occurs sporadically. The cases of familial occurrence constitute only 2% of the total.

So far, 2 genes have been identified on chromosome 3 and 6, the mutations of which may be associated with Moebius syndrome. They are certainly not the only cause of the disease - the confirmed presence of these mutations affects only 6% of patients.

The most probable mechanism of the Moebius syndrome is consideredbrain development disorders in the early stages of embryonic development (around 5 weeks in fetal life). The damage concerns the area of ​​the brain where the nuclei of the VI and VII cranial nerves are located, which explains the paresis of these structures.

It is not known by what mechanism the developmental disorders of the nervous system occur. There are hypotheses about sudden cerebral ischemia, others suggest a connection with intrauterine hypoxia or the possible effects of toxic substances consumed by the mother (drugs, cocaine, alcohol).

So far, we have not found a reason that would explain all the cases of this disease.

Moebius syndrome - diagnosis

The diagnosis of Moebius syndrome can cause many problems. Unfortunately, there is no single test that can confirm the diagnosis. The diagnosis is mainly clinical - Moebius syndrome is diagnosed in patients who show the characteristic symptoms of this disease, after excluding other possible neurological diseases. The basic criterion for the diagnosis of the Moebius syndrome is the presence of unilateral or bilateral palsy of the facial nerve connected with paresis of the abductor nerve.

The presence of accompanying birth defects may speak for the diagnosis, but is not an inherent criterion. In order to rule out other possible pathologies of the nervous system, brain imaging tests are often performed during diagnosis.

Computed tomography may show calcifications inside the brainstem. Such calcifications are evidence of past ischemia of the nervous tissue. Their presence may be helpful in diagnosis, but it does not exclude other possible causes of existing disorders.

Imaging tests in the diagnosis of Moebius syndrome are only auxiliary, and the most valuable thing is a thorough clinical examination of the patient.

Moebius syndrome - treatment

Caring for patients with Moebius syndrome requires a multidirectional approach and cooperation of numerous specialists. Unfortunately, no causal treatment of this condition is possible yet.

The therapy focuses on eliminating the most troublesome effects and symptoms of the disease. The team involved in treating the patient should consist of doctors (surgeons, neurologists, ENT specialists, dentists), physiotherapists, speech therapists and a psychologist.

In the earliest stages of a child's life with Moebius syndrome, the most important role is played by the ability to feed and gain appropriate weight gain. Not all patients show significant sucking and swallowing disorders, but a significant proportion requires special techniquesfeeding and other nutritional interventions. In the event of significant feeding difficulties (especially in the presence of a cleft palate), patients may periodically be fed through a gastric tube.

As the patient develops, depending on his condition and coexisting disorders, it is often necessary to undergo surgical treatment. The most frequently performed operations include cleft palate correction, ophthalmological procedures (including strabismus correction) and limb defects surgery.

A special type of treatment that allows to minimize the paresis of the facial nerve is the so-called "Smile surgery". The procedure is performed by specialists in maxillofacial surgery. A special neuromuscular transplant does not allow to regain full facial expressions, but it significantly improves mouth mobility, speech function and patients' well-being.

Patients with Moebius syndrome should be under the supervision of specialists throughout their lives. The organ of vision requires special attention due to the risk of the so-called dry eye syndrome.

Regular eye checkups, eye protection against solar radiation and special moisturizing drops are a necessary part of eyeball care. Due to the frequent coexistence of oral cavity defects and malocclusions, regular visits to the dentist and orthodontist are also necessary.

Support for people with Moebius syndrome should be focused on their normal functioning in the society. Properly selected physical and speech therapy rehabilitation facilitate achieving full independence.

Some patients require psychological support to help them adapt to the disease and develop strategies to deal with its effects.

Moebius syndrome - prognosis

Moebius syndrome is a complex disorder that can cause many he alth, social and psychological problems. Patients with this disease require constant care of specialists and many medical interventions.

It is worth emphasizing, however, that the Moebius syndrome does not shorten life expectancy. Properly conducted treatment and rehabilitation allow most patients to achieve independence and ensure normal functioning.

Category:

Neurology