Subglottic stenosis is a congenital or acquired narrowing of the subglottic airway. It can be congenital, acquired, iatrogenic, or very rarely, idiopathic. It is defined as the narrowing of the portion of the airway that lies between the vocal cords and the lower part of the cricoid cartilage. In a normal infant, the subglottic airway is 4.5-5.5 millimeters wide, while in a premature infant, the normal width is 3.5 millimeters. Subglottic stenosis is defined as a diameter of under 4 millimeters in an infant. Acquired cases are more common than congenital cases due to prolonged intubation being introduced in the 1960s. It is most frequently caused by certain medical procedures or external trauma, although infections and systemic diseases can also cause it. Signs and symptoms
Symptoms may range from stridor during exercise to complete obstruction of the airway. In idiopathic cases, symptoms may be mistaken for asthma. In congenital cases, symptoms occur soon after birth, and include difficulty breathing, stridor, and air hunger. If the vocal cords are affected, symptoms may include inability to make sound, and an unusual cry. Causes
Most commonly, acquired cases are caused by trauma or certain medical procedures. The condition is more often caused by external trauma in adults. External injuries occur from vehicular accidents or clothesline injuries. Iatrogenic cases can occur from intubation, tracheostomy, and an endotracheal tube cuff pressure that is too high. 17 hours of intubation in adults and 1 week of intubation in neonates can cause the injury.
These two transmembrane proteins are two of four fibroblast growth factor receptors involved in osteoblast differentiation during embryonic development; mutations amongst these receptors are involved in several genetic disorders.There are 40 known mutations, most of which are caused by a missense mutation. FGFR2 is the most commonly mutated gene, a missense at cysteine 342 in exon 9, which creates a gain-of-function. The FGFR2lllc isoform, created via alternative splicing of exon 3 of the FGFR2 gene, uses exon 9 and is used in mesenchymal stem cells to control ossification. However, the mutation constitutively activates the transmembrane protein via a disulfide bond formed incorrectly due to the loss of cysteine 342. FGFR3 is expressed more in the frontal bones during embryonic development, guiding cranial bone development. A point mutation causes constitutive activation of tyrosine in the activation loop, located in the cytosolic region of the protein, leading to accelerated differentiation of frontal osteoblasts, resulting in premature fusion of frontal cranial bones. Diagnosis
Diagnosis of Crouzon syndrome usually can occur at birth by assessing the physical appearance of the infant. Further analysis, including radiographs, magnetic resonance imaging (MRI) scans, genetic testing and CT scans can be used to confirm the diagnosis of Crouzon syndrome. Treatment
Surgery is typically used to prevent the closure of sutures of the skull from damaging the brains development. Without surgery, blindness and intellectual disability are typical outcomes. To move the orbits forward, surgeons expose the skull and orbits and reshape the bone.