Pierre-Robin sequence

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Pierre-Robin sequence

Definition

Pierre-Robin Sequence consists of the micrognathia, (small lower jaw), or retrognathia (lower jaw displaced to the back), glossoptosis (displacement of the tongue into the throat) and obstruction of the airway. It is usually accompanied by a cleft palate (an opening in the roof of the mouth). The term sequence is used to describe the pattern of multiple anomalies derived from a single known prior anomaly or mechanical factor.

Description

Children born with Pierre-Robin sequence are found to have small mandibles (lower jaws), or mandibles that are displaced back, tongues that are pushed back into the throat, and difficulty breathing of varying degrees. They also have difficulty feeding. Pierre-Robin sequence is usually accompanied by a cleft palate. It is also known as Pierre-Robin syndrome.

Genetic profile

Pierre-Robin sequence can occur in association with other syndromes; isolated (not associated with other malformations); or in associations with other developmental disorders that do not represent a specific syndrome. Heredity has not been proven to be a factor in the cause of isolated Pierre-Robin sequence. Pierre-Robin sequence found in association with numerous syndromes may have a mode of inheritance that is related to the syndrome itself. The mode of inheritance includes single gene as well as chromosomal abnormalities .

The cause of the abnormal lower jaw in Pierre-Robin syndrome may be mechanical, genetic, teratogenic, or multi-factorial. Mechanical factors such as fibroids inside the uterus may constrict the lower jaw preventing it from growing. Single gene or chromosomal abnormalities produce syndromes that have Pierre-Robin sequence. Teratogenic (anything that affects development of the embryo) causes include maternal use of alcohol. Multi-factorial inheritance means that the cause is a combination of environmental and hereditary factors.

Demographics

The incidence of Pierre-Robin sequence is reported to be one out of 8,500 live births. Other reports show that the range is one out of 2,000 to one out of 50,000 live births. This wide range is due to different diagnostic criteria and the presence or absence of associated syndromes. Fewer than 20% of newborns born with Pierre-Robin sequence have the isolated type.

Signs and symptoms

In Pierre-Robin sequence, the lower jaw of the fetus displaces the tongue backwards into the throat. The tongue located in this abnormal position blocks the embryonic structures from joining in the midline in order to form the palate, the roof of the mouth. The result is a cleft palate, which is an opening in the roof of the mouth. The size of the cleft palate varies as well as its position. It is not present in all patients.

Babies born with Pierre-Robin have difficulty feeding and breathing because the tongue—pushed backwards by the lower jaw—obstructs the throat. Feeding and breathing difficulties may be very mild or very severe.

Affected persons may also develop hearing problems due to fluid collecting in the ears.

Diagnosis

Prenatal ultrasonic examination may show findings to indicate the possibility of Pierre-Robin sequence alerting the physician to be prepared at birth for the possibility of the baby having breathing and feeding problems.

Treatment and management

The type of treatment varies according to the severity of the symptoms and their duration. Babies may not require any therapy if they have no symptoms of breathing difficulties and no feeding difficulties

If breathing difficulties are mild, the easiest management is keeping the baby in the prone position. This position causes the tongue to fall forward, relieving the obstruction. A thorough evaluation of these patients must be conducted, which includes endoscopy of the airways and upper digestive tract. Close monitoring must be maintained because the prone position may obscure breathing difficulties.

If positioning the patient prone fails, a nasopharyngeal airway may be used but only for a short time. The airway is a tube passed through the nose into the upper airway, which the baby can breath through.

If the above methods fail or are required for a prolonged length of time, then some type of surgical intervention will be required. Surgical procedures include glossopexy, in which the tongue is sutured to the lower lip in order to prevent it from moving back into the throat causing obstruction. Subperiosteal release of the floor of the mouth muscles on the lower jaw is an operation in which the tongue can no longer move back into the throat because muscles are released from their insertions. Tracheotomy is performed by surgically cutting an opening in the trachea (windpipe). This opening bypasses the obstruction. The choice of surgical intervention varies according to the duration and severity of respiratory obstruction; other causes of respiratory obstruction that may be present; and the experience of the surgeon. Glossopexy and tracheotomy are temporary and reversed when the baby can breath adequately on its own.

The treatment of feeding difficulty varies according to the degree of difficulty. It has been found that the severity of feeding difficulty is proportional to the severity of airway obstruction. Feeding is usually accomplished with specialized cleft palate nipples and bottles or nasogastric tubes (a feeding tube passed through the nose and into the stomach). Sometimes a gastrotomy tube is needed for feeding. This is a tube passed through a surgical opening made in the abdominal wall and stomach.

Children with Pierre-Robin sequence are prone to hearing loss due to fluid collecting behind the tympanic membrane (ear drum), and may require drainage tubes placed into the ear.

If the child has a cleft palate, it is usually surgically repaired between the ages of nine and 18 months.

Prognosis

The prognosis for individuals with Pierre-Robin sequence varies with the severity of symptoms and if it is associated with other congenital abnormalities. The more severe the symptoms and associated congenital abnormalities, the greater the risk of complications.

The rate at which the lower jaw starts to catch up in growth depends on the cause of Pierre-Robin sequence. The majority of children with the isolated type will achieve near normal jaw size within a few years of birth. If Pierre-Robin sequence is part of a syndrome that has a small jaw, the jaw may remain small throughout life.

Resources

PERIODICALS

Bath, A. P. "Management of the upper airway obstruction in Pierre Robin Sequence." Journal of Laryngology and Otology 111, no. 12 (December 1997): 1155–7.

Cohen, N. M. Jr. "Pierre Robin Sequences and complexes: causal heterogeneity and pathogenetic/phenotypic variability." (Editorial). American Journal of Medical Genetics 84, no. 4 (June 4, 1999): 311–5.

Cruz, M. "Pierre Robin Sequences: secondary respiratory difficulties and intrinsic feeding abnormalities." Layrngoscope 109, no. 10 (October 1999): 1632–6.

Hsieh, Y. Y. "The Prenatal Diagnosis of Pierre Robin Sequence" Prenatal Diagnosis 19, no. 6 (June 1999): 567–9.

Marques, I. L. "Etiopathogenesis of isolated Robin Sequence." Cleft Palate-Craniofacial Journal 35, no. 6 (November 1998): 517–25.

Myer, C. M. "Airway management in Pierre Robin Sequence." Otolaryngology–Head and Neck Surgery 118, no. 5 (May 1998): 630–5.

Prows, C. A. "Beyond Pierre Robin Syndrome." Neonatal Network 18, no. 5 (August 1999): 13–9.

Van Der Haven. "The Jaw Index: New guide defining Micrognatia in newborns." Cleft Palate-Craniofacial Journal 34, no. 3 (May 1997): 240–1.

Vester, F. "Pierre Robin Syndrome: Mandibular growth during the first year of life." Annals of Plastic Surgery 42, no. 2 (February 1999): 154–7.