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Metatropic dysplasia
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see also spondylo-epi-metaphyseal dysplasias
Prevalence inferior to 1/106. . Mutation of the TRVP4 gene that codes for a calcium channel. This is a subtype of spondylo-epi-metaphyseal chondrodysplasia with heterogeneous clinical presentation:.
Different types:
- type I: autosomal recessive, lethal form
- type II: autosomal recessive form with survival until childhood
- type III: autosomal dominant form, the most common
- type IV: moderate form the type of transmission of which remains uncertain.
Clinical features:
- short limbs with enlarged metaphyses ("dumbbells"-shaped long bones)
- short stature: adult maximum height 1.2 m
- trunk of normal stature at birth (seems long in comparison with the length of the limbs) which gradually shortens due to the appearance of kyphoscoliosis (flattened vertebrae and enlarged intervertebral space) with anterior protrusion of the sternum
- early calcification of hyoid and cricoid cartilages, with tracheomalacia and anomalies of the shape and the position of the epiglottis
- square iliac wings
- fusion of some cervical vertebrae and sometimes subluxation of C1 - C2 due to hypoplasia of the odontoid process (requiring a cervical arthrodesis); a fixed torticollis is present in more than 50 % of cases
- sometimes appearance of hydrocephalus due to stenosis of the spinal canal or of the occipital foramen
- high forehead, broad and flattened root of the nose, sometimes cleft palate
Anesthetic implications:
short stature with kyphoscoliosis; risk of cervical spine instability (C1 - C2); look for signs of intracranial hypertension. To facilitate mask ventilation and intubation, it is useful to put pillows under the upper chest and a roll under the shoulders to align the clavicle with the mastoid process and bring the chin upwards. Risk of difficult intubation, that increases with age, especially if a cervical arthrodesis has been performed. The cricoid is often positioned below the manubrium, which renders tracheotomy difficult.
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EXPERT CONSENSUS for MANAGEMENT:
Surgical morbi-mortality is higher than in the normal population and the risk of anesthetic complications is very high: these patients must therefore be managed in facilities where care of those complications can be taken. It is why : - a full neurological examination is necessary before general or locoregional anesthesia - imaging (MRI or CTscan) of the full spine is recommended - a flexion/extension MRI of the cervical spine is necessary if there is any concern about its stability - polysomnography, respiratory functional tests (restrictive or obstructive syndrome) and cardiac evaluation (echocardiography) must be considered before an anesthesia - morphological and functional anomalies of the upper airway, a decrease in mobility of the cervical spine and bronchial airway anomalies increase the morbidity and mortality of anesthesia - a sedative premedication can be administered before anesthesia - for intubation, a videolaryngoscope and a intubating fiberscope must be immediately available - tracheostomy can be extremely difficult in those patients, particularly in emergency; it is crucial to identify the position of the cricothyroid membrane (XRays, echography) before anesthesia - extubation must be preferably done in the operating room; if this may not be the case, an experienced team must be present - in patients in whom a fragility of the spinal cord is suspected (concept of spinal cord at risk : significant cyphosis, risk of hypotension, long lasting surgery, difficult surgical positioning), neurological monitoring must be done during the whole procedure, and it is better to avoid epidural anesthesia Reference:
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References:
- El-Kettani E-C, Chat L, Najid A, Dafiri R.
La dysplasie métatropique: à propos de deux frères.
Arch Pédiatr 2003; 10: 989-93.
- Theroux MC, Lopez M, Olszewsky PJ, DiCindio S, Arai L et al.
Metatropic dysplasia: a skeletal dysplasia with challenging airway and other anesthetic concerns.
Pediatr Anesth 2017; 27: 596-603.
Updated: December 2017