Moebius syndrome is a nonprogressive craniofacial/neurological disorder that manifests itself mostly in facial paralysis. It is a rare neurological disorder that is characterized by weakness or paralysis of multiple cranial nerves, most often the 6th (abducens) and 7th (facial) nerves. Other cranial nerves are also affected sometimes.
Congenital facial and abducens palsy was first described by Von Graefe (1880) and Moebius (1888), a German neurologist after whom the syndrome was named after.
Moebius Syndrome is also known by the following names:
- Moebius sequence
- Congenital facial diplegia syndrome
- Congenital oculofacial paralysis
- Mobius syndrome
- The disorder is present at birth (congenital).
- If the 7th nerve is involved, the individual with Moebius syndrome is unable to smile, frown, pucker the lips, raise the eyebrows, or close the eyelids, and if the 6th nerve is affected, the eye cannot turn outward past the midline.
- Other abnormalities include underdevelopment of the pectoral muscles and defects of the limbs
- The exact cause of Moebius syndrome is unknown and appears to occur randomly (sporadically) in most cases. However, some cases occur in families suggesting that there may be a genetic factor.
- Many individuals with Moebius syndrome also have skeletal involvement with limb abnormalities (Poland syndrome) and can have respiratory problems, speech and swallowing disorders.
- They can also have visual impairments, sensory integration dysfunction; sleep disorders, weak upper body strength, and autism spectrum disorders.
- Many people with Moebius syndrome are born with a small chin (micrognathia) and a small mouth (microstomia) with an unusually shaped tongue. The roof of the mouth may have an abnormal cleft palate or be high and arched, and these abnormalities contribute to problems with speech, which occur in many children with Moebius syndrome.
- Dental abnormalities, including missing and misaligned teeth, are also common.
Signs & Symptoms of Moebius Syndrome
The abnormalities and severity of Moebius syndrome vary greatly from one person-to-another, and the classically accepted diagnostic criteria include facial paralysis or weakness affecting at least one but usually both sides of the face, paralysis of sideways (lateral) movement of the eyes, and preservation of vertical movements of the eyes.
Sometimes, other cranial nerves, including the 5th, 8th, 9th, 10th, 11th, and 12th may be affected. In a clearer way, symptoms of the disease are:
- Lack of facial expression and inability to smile
- Feeding, swallowing and choking problems, resulting in keeping head back to swallow
- Eye sensitivity due to inability to squint and absence of lateral eye movement
- The absence of blinking and Strabismus (crossed eyes)
- Motor delays due to upper body weakness
- Drooling, High palate, Short or deformed tongue, and Limited movement of the tongue
- Dental problems and Hearing impairment
- Articulation and speech disorders
- Hand and feet deformities
Causes of Moebius Syndrome
Most cases of Moebius syndrome occur randomly for unknown reasons. The syndrome is listed as Online Mendelian Inheritance in Man (OMIM) Number 15700, and sporadic mutations in PLXND1 and REV3L genes have also been identified in a number of patients and confirmed to cause a constellation of findings consistent with Moebius syndrome when introduced in animal models.
In rare cases, family patterns have been reported, meaning that Moebius syndrome may be multifactorial (both genetic and environmental factors play some causative role).
It is believed that in different cases of the rare disease, there are different underlying causes.
In some family cases, there is evidence that Moebius syndrome is inherited as an autosomal dominant trait. The abnormal gene can be inherited from either parent or can be the result of gene change (mutation) in the affected individual.
Findings in Moebius syndrome suggest a developmental defect of the hindbrain, and several different theories have been proposed to explain the cause of Moebius syndrome. One assumption is that the disorder is the result of diminished or interrupted blood flow to a developing fetus during pregnancy.
This lack of blood flow could be as a result of an environmental, mechanical or genetic factor/cause. All the same, the cause or causes of the syndrome remains inconclusive and more basic and clinical research is needed.
Diagnosis And Treatment
A good diagnosis of Moebius syndrome should be based upon the characteristic symptoms, a detailed patient history, and a thorough clinical evaluation.
There are no diagnostic tests that confirm a diagnosis of Moebius syndrome, and some specialized tests may be performed to rule out other causes of facial palsy.
The treatment of Moebius syndrome is directed toward the specific abnormalities in each individual and usually managed by a multidisciplinary team, often in a craniofacial center.
Involved specialists in such team include:
- plastic surgeons;
- ear, nose, and throat specialists (otolaryngologists);
- dental specialists;
- speech pathologists;
- specialists who assess and treat hearing problems (audiologists),
- specialists who treat eye abnormalities (ophthalmologists) and
- Other healthcare professionals.
Corrective procedures for facial paralysis involve the transfer of muscle or graft nerves from another area of the face or the body, while an old procedure, known as a temporalis tendon transfer, involves taking the temporalis muscle (muscles used for chewing/mastication) and transferring it to the corners of the mouth.
This same type of operation can be also used to improve closure of the eyelids, and if the paralysis is on only one side (unilateral), a “cross-facial nerve graft” is an option.
The most recent procedure, that has shown remarkable results in terms of speech, facial mobility and self-esteem involves the microvascular transfer of a muscle from the thigh to the face and connecting the nerves that normally supply the masseter muscle (muscles used for chewing).
Frequent lubrication for dry eyes is often necessary, and physical therapy may be needed for individuals with various orthopedic abnormalities.
Splints, braces, and prostheses may be necessary for individuals with congenital limb abnormalities, and genetic counseling may be beneficial for affected individuals and their families.
Temporalis Tendon Transfer For Moebius Syndrome
The temporalis muscle is one of the muscles that we use for chewing and is one of the strongest and most dynamic muscles in our body. The trigeminal nerve (cranial nerve 5) is responsible for the activity of the temporalis muscle, and since this nerve is generally unaffected by Moebius Syndrome, we can use this muscle to achieve facial reanimation.
According to Dr. Azizzadeh, the temporalis transfer procedure has been very successful in rehabilitating dynamic facial movement and creating facial symmetry for patients with Moebius Syndrome.