Glottic stenosis describes a fixed narrowing of the upper airway at the level of the glottis. The glottis is the portion of the larynx containing the vocal cords and the glottic opening. Anatomically, the glottis is the part of the larynx extending from the junction between the true and false vocal cords at the apex of the laryngeal ventricle to a line one centimeter below the inferior aspect of the vocal cords. The anterior two-thirds of the glottis is the glottis vocalis, while the posterior third is known as the respiratory glottis. Glottic stenosis is part of a broader pathology, laryngeal stenosis, which can be glottic, supraglottic, or subglottic. It can be congenital or acquired, and its management is complex, as it requires airway, voice, and laryngeal competence preservation.
Glottic stenosis can be either congenital or acquired. Congenital glottic stenosis is very rare. It manifests as an incomplete recanalization of the laryngeal lumen during fetal development, which occurs at the end of the third gestational month. In a closer look at the embryologic origin of the airway, the larynx itself forms by the recanalization of the fetal laryngeal lumen. Complete failure of recanalization results in laryngeal atresia. Congenital glottic stenosis can present as thin membranous stenosis, a thick anterior or posterior web, or even as complete fusion of the vocal cords.
Acquired glottic stenosis is more common and has multiple etiologic factors. The most frequent is trauma secondary to endotracheal intubation, which is thought to occur due to the tube’s pressure effect causing tissue ischemia, inflammation and scarring. The risk of glottic stenosis is related to the duration of the intubation, the size of the endotracheal tube, the number of intubations, and excess movement of the endotracheal tube in agitated patients. Other trauma-related causes include foreign bodies, caustic ingestion, irradiation, and external trauma (blunt or penetrating). Also, prolonged nasogastric intubation causes mucosal ulceration which may progress to posterior stenosis. Finally, iatrogenic trauma after aggressive endolaryngeal surgery could also lead to stenosis.
A variety of infectious diseases such as syphilis, fungal infections, and diphtheria can cause glottic stenosis. Additionally, granulomatous diseases such as tuberculosis, sarcoidosis, rhinoscleroma, and granulomatosis with polyangiitis (GPA) are thought to cause the condition. Rare etiology of glottic stenosis includes mycosis in immunosuppressed patients, leprosy, mucous membrane pemphigoid, and scarlet fever.
Gastro-oesophageal reflux is thought to be a contributing factor; however, its role in the aggravation of the disease remains unclear at present.
Post endotracheal intubation stenosis is the most common type of glottic stenosis. The risk of developing stenosis in intubated patients has been found to be between 6% and 19% based on two prospective studies realized in the long term intubated patients, particularly in those intubated for five days or longer. Congenital glottic stenosis is very rare, and the most extensive study performed identified 51 children in 32 years.
Acquired glottic stenosis thought to be caused by mucosal ulceration which leads to infection, perichondritis, and cartilage necrosis leading to granulation tissue formation over the vocal process of the arytenoid cartilage. Subsequently, scar formation and fibrosis cause contraction and arytenoid fixation.
In some cases with complex presentations, where the diagnosis is not certain, tissue biopsies and histological analysis is necessary. The presence of abscess of caseous necrosis or vasculitis differentiates various pathologies such as tuberculosis, sarcoidosis, or Wegener's granulomatosis. Further, microbiological tests can determine the presence of infectious pathogens.
The clinical presentation of glottic stenosis is variable and depends on the cause and the severity of the stenosis. The most common presentation of laryngeal obstruction is stridor. The level of the airway obstruction determines the nature of the abnormal breathing sounds. Upper airway obstruction results in mostly inspiratory stridor while obstruction in the lower respiratory tract results in expiratory or biphasic stridor.
Congenital glottic stenosis presents with airway distress, a weak and husky cry, and occasionally, aphonia. Infants with severe airway distress require emergency intubation or tracheostomy soon after birth. Children with milder glottic stenosis can remain completely asymptomatic until they develop a respiratory infection. Airway edema and thick secretions can lead to increased work of breathing and upper airway obstruction symptoms. Finally, children with recurrent croup require investigation for upper airway stenosis including at the level of the glottis.
Acquired glottic stenosis symptoms depend on the severity and location of the stenosis. Respiratory symptoms are the predominant symptoms in posterior glottic stenosis while anterior glottic webs mainly present dysphonia. In general, patients may present with respiratory distress, episodes of apnoea, dyspnoea, or tachypnoea. Other symptoms include hoarseness, alteration of voice, and aphonia. Dysphagia and aspiration may also be present.
History needs to concentrate on the assessment of dyspnoea and stridor, the onset and severity of the symptoms as well as the aggravating and relieving factors. Also, the voice should be thoroughly assessed. Finally, history should focus on the etiology, including previous episodes of intubation, trauma, infectious and inflammatory processes as well as co-morbidities.
Flexible fibreoptic endoscopy is the gold-standard for the initial glottic stenosis diagnosis. It can be performed on awake patients whether they are adults or infants. Microlaryngoscopy under general anesthesia is essential to assess the severity of the glottic stenosis and exclude other airway pathology. The mobility of the arytenoids at the cricoarytenoid joints can be evaluated with palpation. Biopsy of the stenotic area can help determine the cause of the condition and may be therapeutic also.
Imaging and Other Studies
Lateral soft tissue neck plain radiographs have limited value, but they can be useful occasionally if a foreign body is suspected. Video-fluoroscopy is also a valuable tool to assess swallowing function which might impact treatment decisions. CT scan of neck and thorax can demonstrate the severity of the stenosis and the co-existence of any other pulmonary issues. 3D segmentation can be useful for surgical planning. Other investigations include voice analysis and pulmonary function tests. Electromyography can help differentiate glottic stenosis from bilateral vocal cord paralysis. Few laboratory tests are helpful with glottic stenosis diagnoses, such as inflammatory markers and serology workup in cases where granulomatous diseases are suspected.
The management of glottic stenosis is variable and complicated, and it requires individualized treatment by experts in laryngeal pathologies. The primary concern is to secure the patient’s airway. However, voice and laryngeal function preservation are of nearly equal significance.
Congenital glottic stenosis can often be managed with careful observation or via an endoscopic approach to divide the anterior web. The use of laryngeal stents or tracheostomy might be necessary in severe cases. If there is an antenatal diagnosis of congenital high airway obstruction syndrome (CHAOS), the neonate’s airway must be secured using ex-utero intrapartum treatment . Gas exchange via the placenta and umbilical cord requires careful maintenance until a decision regarding a definitive airway, which is either intubation or tracheostomy.
In cases of glottic stenosis due to infectious or inflammatory conditions, medical management is the mainstay of treatment. Early diagnosis and treatment of the underlying medical condition can result in improvement of the glottic stenosis and eliminate the need for further surgical management.
There are two primary surgical means to approach acquired glottic stenosis: endoscopic and open procedures. Anterior thin webs are easily manageable with dilatations or laser/blade incision. Thicker webs require more complex management and the risk of restenosis is considerable. In these cases an effective endoscopic approach involves performing scar excision, resurfacing with mucosa, and stenting. In posterior glottic stenosis, endoscopic posterior cricoid split and rib grafting have shown promising results.
Several medical therapeutic adjuncts are used to support endoscopic treatment of glottic stenosis including botulinum toxin, steroids, and mitomycin C to be the most effective. The botulinum toxin results in a temporary paresis of the adductor muscles when injected in the interarytenoid and thyroarytenoid muscle. Consequently, this prevents over-adduction in the posterior commissure and post-operative healing improves while reducing the risk of restenosis. Mitomycin C inhibits fibroblast proliferation reducing the risk of restenosis and scaring. Steroid injection into the posterior glottis can be effective in reducing inflammation and granulation tissue formation. However, the use of systemic steroids is controversial, and treatment should be individualized as they decrease scar tissue formation, but at the same time, they reduce the healing ability.
Failure of endoscopic procedures or thicker laryngeal webs require open surgical techniques. A laryngofissure is necessary with a subsequent open laryngeal repair with dissection of the web. A laryngeal stent or Silastic keel is often used to keep the laryngeal lumen open while the mucosal surfaces are healing. Various grafts have been used to cover the raw area such as skin grafts, endonasal or buccal mucosa, and perichondrium-cutaneous composite grafts. Rib cartilage grafts can be used to widen the glottis and subglottis.
Glottic stenosis requires differentiation from bilateral vocal cord palsy. It can prove difficult to reach the correct diagnosis as the two conditions have similar presentations and triggering events. Electromyography, flexible nasendoscopy and examination under anesthesia can assist in differentiating between the two. Other differentials include :
Cohen’s classification of congenital glottic webs is as follows, and is similar to the older Cotton grading system:
Airway stenosis involving the glottis is challenging in terms of management and good functional outcomes. It requires expertise in addressing the condition and treatment often requires several procedures as the stenosis reoccurs. Involvement of the glottis leads to poor outcomes after laryngotracheal reconstruction compared to stenosis in other anatomical sites. The other risk factor for poor outcome is the patient’s comorbidities. Opinions are divided when it comes to the best surgical technique. Some experts believe that medical and endoscopic options should be exhausted first and surgical approaches should be considered afterward while others think that open procedures have better outcomes when tried first. Voice outcomes vary considerably, but the voice tends to improve after the stenosis treatment.
Usual postoperative complications such as bleeding, wound infection, subcutaneous emphysema, or neurological and vascular compromise are often managed conservatively. Complications that require emergency management are airway obstruction, stent aspiration, hematoma, and pneumothorax. Airway obstruction is managed with intubation or emergency tracheostomy while stent aspiration requires urgent bronchoscopy for foreign object removal. Management of hematoma and pneumothorax is by drainage. Mucus and secretions can also cause airway obstruction and require immediate suction. Other complications include stenosis recurrence, chronic aspiration, infection, keel extrusion, chondritis, dysphonia, granulation tissue formation, and tracheostomy dependence.
Patients should be encouraged to attend an emergency department if they develop sudden or worsening airway obstruction symptoms; this is particularly important in the post-operative period. Education and training are vital in airway stenosis patients and their carers. Pediatric basic life support and tracheostomy management are essential skills for parents of children with congenital glottic stenosis. Patients should receive information regarding the recurrent nature of glottic stenosis and the need for repeated procedures. However, patients should be encouraged that good long-term outcomes are achievable, but it requires time, and regular follow up visits.
Glottic stenosis is an excellent example of an interprofessional team approach. Different specialists with various skills and responsibilities are needed to address this condition successfully. The primary provider of patient care is the ear nose and throat specialist who cooperates with multiple other healthcare professionals to achieve a good outcome. Other members of the team could include depending on the patient pathology, physicians, pediatricians, specialized anesthesiologists, radiologists, head and neck nurses, and speech and language therapists. Thus an interprofessional approach enhances patient safety and ensures that the delivery of the best quality of care for optimal patient outcomes.
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