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Pierre Robin Sequence

What is Pierre Robin Sequence?

Pierre Robin Sequence is a condition of multiple anomalies arising from the primary pathology of mandibular hypoplasia or micrognathia, an under-development of the lower jaw. Other anomalies that present are: retrognathia, positioning of the lower jaw too far back in relation to the top jaw and other facial structures; glossoptosis, a displacement of the tongue (due in part to the reduced area of the oral cavity) up and to the back of the hard palate; cleft palate (either "U" or "V" shaped); and breathing problems.
Pierre Robin sequence is often referred to as Pierre Robin syndrome. It is no longer considered a syndrome because by definition, a syndrome is a collection of anomalies resulting simultaneously from one condition. Pierre Robin is a sequence because all of its anomalies result, sequentially, from the malformation of the lower jaw. The micrognathia causes glossoptosis, which can cause cleft palate.
Pierre Robin sequence can be an isolated condition or it can be part of another syndrome (like Stickler's Syndrome or Treacher Collins Syndrome). It is important to determine which is the case at the time of diagnosis in order to determine a course of treatment.

Etiology

Pierre Robin Sequence is typically diagnosed at birth. It is generally not regarded as solely attributed to genetic abnormalities. Cause of the primary anomaly are thought to be related to the position of the fetus during the 7th and 11th week of gestation.

Nervous System

In PRS, most cases reflect an absence of the pharyngeal reflex (“gag reflex”). Innovated by the glossophayngeal nerve (cranial nerve IX), and the vagus nerve (cranial nerve X), together these nerves provide an autotomic system that prevents choking. This reflex contracts the pharyngeal muscles and closes off the throat when an object, outside of normal swallowing, tries to pass through. However due to the presence of a severe cleft palate, the absence of this reflex presents a high risk of potential choking.

Respiratory System

Glossoptosis and Microganthia both present severe respiratory problems in patients with Pierre Robin. With weakened tongue muscles, certain ways that patients position themselves or are positioned can cause the tongue to sit 'floppily' at the back of the mouth. This posterior placement of the tongue, in comparison to the small recessed jaw, can easily cause obstruction due to the tendancy of the tongue falling backward and blocking the airway. Which in turn, prevents the free flow of air.

Phonatory System

The phonatory system is the source of all voiced sound. The quality of our voice is affected by the airstream from our lungs, the shape and function of various structures in our throat, and the shape and function of our nose and mouth. The most prevalent facial malformation associated with Pierre Robin sequence is micrognathia, or the underdevelopment of the lower jaw. This often causes glossoptosis, which is a displacement of the tongue, due to a lack of sufficient space within the lower jaw. The displaced (and often too large for the small mouth) tongue can block the airway, interfering with the ability to generate a steady enough airstream for speech. As we speak, we block our airstream from going through our nose, so we can produce sounds using our mouth. The prevalence of cleft palate in individuals with Pierre Robin sequence can make it difficult to produce speech sounds, due to air escape through the nose.


Articulatory System

As a result of Pierre Robin sequence, two of the largest mobile articulators used for speech production are affected: the lower jaw and tongue. An anomaly such as a cleft to the soft and/or hard palates may also present as part of the sequence but is not always present in the diagnosis.

In Pierre Robin sequence the mandible is either micrognathia, where the mandible is small, or retrognathia, where the mandible is normal-sized but the cranial base angle is much larger than normal.(2) Because of the abnormal development of the mandible the oral cavity area is reduced. During fetal development the tongue is displaced to the posterior of the oral cavity which may impede the joining of the palatine plates causing a cleft of the palate.
Due to the blockage of the airway by the displaced tongue, the primary concern for infants born with this sequence is to keep the airway open. PRS infants often require feeding tubes until the mandible has "caught up" in growth to the rest of the articulatory system to allow the child to feed orally.

Auditory System

One of the defining characteristics of PRS is cleft palate. Depending on the severity of the cleft, it can lead to Otitis Media (ear infection) with Middle Ear Effusion (fluid in the middle ear). As a result of repeated ear infection, individuals with Pierre Robin often have conductive hearing loss. PRS can also include inadequate pneumatization (air cavity development within the bone) in the bones involved with hearing. A lack of normal air cavities within these bones can result in muffled hearing.


Overall effect on speech production

Language development may be delayed due to poor articulation of the tongue, impaired movement and ability to purse the lips, crowding of the teeth and velopharyngeal insufficiency. Velopharyngeal insufficiency will affect production of fricatives and glottal stops. Without surgical repair of clefts and early intervention by a speech pathologist, a child may develop "compensorary articulation."

Treatment

Treatment for Pierre Robin varies greatly from case to case. Most often, the first move is to repair the cleft palate. This is done surgically in a few different ways. In some cases, a palatal obturator can be used. This is a prosthesis inserted in the gap that blocks the opening. The doctor may choose to either replace the obturator with larger ones as the child grows, or replace it with smaller ones so that the bone will grow toward it to compensate for the space created during growth. Another surgical option for cleft palate is to insert a Latham Appliance. This is similar to a palate expander orthodontists commonly use. Once it is installed, a key is turned daily to tighten it. This brings the bone closer together and will gradually close the gap. An additional option is to fill in the gap created by the cleft using the patient's own bone tissue, usually harvested from the hip or rib.
In some cases, it is necessary to correct the underdevelopment of the lower jaw. This can be done via a process called mandibular distraction osteogenesis. A distractor (like an orthodontic palate expander) is installed at a vertical cut in the mandible. The distractor is attached to the bone by two pins on each side that go through the skin and soft tissue into the bone. The space between these two pins is lengthened gradually by turning screws on the distractor. As the space is lengthened, new bone grows in to fill it in. Eventually, the jaw is moved forward enough for proper alignment. This usually takes about six weeks. The distractor is left in place for approximately one more week to allow the new bone to harden.
Many children with PRS have difficulty maintaining an open airway, as a result of the glossoptosis. In some cases, doctors perform a procedure called tongue-lip adhesion. In this procedure, the tongue is stretched forward and stitched to the bottom lip to prevent it from falling into the airway. The tongue is detached from the lip once the facial structures have grown enough to keep the airway open on their own. An additional treatment option for glossoptosis is a nasal trumpet. A nasal trumpet is a small tube inserted through the nose, into the airway to keep it open, even if the tongue gets in the way. The nasal end of the tube is flared to keep it from getting stuck in the nose, giving it a trumpet-like appearance. This is also a temporary solution, often done while the child awaits surgery.




External Links


Basic Info: http://www.clapa.com/medical/pierre_robin_article/110/

Chase's Story: http://www.skippercat.com/ pierrerobin.com/


Parent Info and Support: http://pierrerobin.org/caring- for-your-child.htm


Reference List