Beyond Achondroplasia

Growing together with Clara

Midfacial hypoplasia in achondroplasia: How surgery can rescue the upper respiratory function

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One of achondroplasia caracteristics is midface hypoplasia, a facial dysmorphology.

Hypoplasia is the underdevelopment or incomplete development of a tissue or organ. In this case, midface hypoplasia (blue region in the image) is the maxillary bone region hypoplasia and or depressed nasal bridge.

In midfacial hypoplasia, the center of the face develops more slowly than the eyes, forehead, and lower jaw. When mild, this is generally considered to be a harmless genetic variation. In more severe cases, however, the condition is so pronounced that both appearance and health may be affected.

In dwarfism, the extent of the hypoplasia is generally mild and requires intervention only when severe enough to cause complications, namely cases of severe sleep apnea or airway obstruction.

Here is a very interesting article: Distinct patterns of respiratory difficulty in young children with achondroplasia: a clinical, sleep, and lung function study

Many children with achondroplasia have midface hypoplasia in combination with adenoids and tonsil hypertrophy that can lead to obstructive sleep apnea (OSA). Most undergo adenotonsillectomy surgery. However, airway obstruction might not always be attributed solely to adenotonsillar hypertrophy, either because clinical problems persisted after surgery or because radiology did not confirm encroachment on the airway by adenotonsillar tissue. Upper airway soft tissue abnormalities as redundante oropharyngeal tissue might my the cause of OSA, as Clara showed.

Depending of severity of obstruction and response to treatment, options can include adenoidectomy, tonsillectomy, Continuous Positive Airway Pressure (CPAP) or bipap, uvulectomy and uvulopharyngopalatoplasty. But some will have refractory obstruction with persistent OSA syndrome and require a tracheostomy. In nearly all of those, tracheostomy need is transient.

In exceptional cases, there is also possible to have a surgical approach in severe midfacial hypoplasia: distraction osteogenesis. Some might interpret this approach as a merely aesthetical surgery, but it can be a life improvement surgery.

Distraction osteogenesis has been established as a useful technique in the correction of skeletal anomalies of the long bones for several decades. However, the use of this technique in the management of craniofacial deformities has been evolving over the past 20 years, with initial experience in the mandible, followed by the midface and subsequently, the cranium.

In the following articles, you can see some examples of procedures of distraction osteogenesis:

Frontofacial monobloc distraction in the very young: a review of 12 consecutive cases, Ahmad el al, 2012

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Image from the article Segmental distraction osteogenesis with modified LeFort II osteotomy for a patient with craniosynostosis , AJO-DO

Midface Distraction to Alleviate Upper Airway Obstruction in Achondroplastic Dwarfs, Elwood et all, 2003

“Respiratory complications are common with achondroplasia secondary to small chest size, sleep-disordered breathing, hypotonia, and upper airway obstruction. Upper airway obstruction may lead to multiple complications ranging from sleep disturbance, enuresis, somnolence, obstructive apnea, cor pulmonale and cardiorespiratory collapse. Right-sided heart failure may rarely lead to severe congestive liver damage with hepatic failure and coma. Tracheostomy may be required to prevent upper airway obstruction and accompanying hypoxemia.

The airway zone concept explains that for obstructive apnea, there are usually multiple levels of obstruction, and each level can be individually addressed to relieve obstruction and thus avoid tracheostomy. Achondroplasia is an ideal setting to apply this concept because the syndrome usually manifests with several levels of airway obstruction.

The use of midface distraction osteogenesis in patients with either achondroplasia or upper airway obstruction secondary to midface hypoplasia has not been previously described. This report details two cases of tracheostomy-dependent patients with achondroplasia-related obstructive sleep apnea who that had their tracheotomies success decannulated after midface distraction”.

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Image from article. Case 1, a 3-year-old girl with severe midface hypoplasia and airway obstruction.

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Image from article. Case 1 after 25mm maxillary distraction and successful decannulation

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Dr. Fernando Molina, that attended the international congress around achondroplasia and other skeletal dysplasias, is a world renowned plastic surgeon with a training in craniofacial surgery and to him, belong the largest clinical series on Distraction Osteogenesis around craniofacial skeleton worldwide.

 

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