Laboratory Studies
Few diagnostic laboratory findings are associated with glottic stenosis, although performing a serologic workup is necessary if a granulomatous disease (eg, sarcoidosis, tuberculosis, syphilis, Wegener granulomatosis) or a systemic disease (eg, rheumatoid arthritis, amyloidosis) is suspected as the cause.
Imaging Studies
Routine plain upper airway and chest radiographs are of limited value in the diagnosis and treatment of glottic stenosis but may provide an initial assessment of laryngotracheal air column and coexisting pulmonary disease.
A CT scan allows for evaluation of the length and thickness of the glottic stenotic segment in subglottic stenosis. A CT scan also allows for evaluation of the laryngeal framework in order to determine the presence of a fracture or other significant injury.
Spiral CT scanning with 3-dimensional reconstruction is advisable for better surgical planning and outcome, and it is complementary to rigid endoscopy in the management of these conditions. [4]
Other Tests
Pulmonary function tests (ie, maximum inspiration and expiration flow rates, flow volume loops, pressure flow loops) show characteristic changes in upper airway stenosis and may be used to compare preoperative and postoperative results.
Electromyography (EMG) can help to differentiate posterior glottic stenosis from bilateral vocal cord paralysis. It may also be used to evaluate the function of the intrinsic muscles of the larynx.
Twenty four-hour pH studies help to evaluate coexistent gastroesophageal reflux.
Diagnostic Procedures
First, the conscious patient's vocal cord mobility is assessed using either indirect laryngoscopy or fiberoptic laryngoscopy. Currently many clinicians are advocating early evaluation of the larynx (ie, within the first few hours after extubation) to diagnose and commence treatment of lesions caused by prolonged endotracheal intubation.
Subsequently, under anesthesia, direct laryngoscopy and bronchoscopy in the operating room allow for careful evaluation of the laryngeal and distal airways and provide a means of assessing the cricoarytenoid joints.
Microlaryngoscopic assessment helps to identify the extent and character of the stenosis and the degree of arytenoid mobility and to determine if cricoarytenoid joint fixation is present. Posterior glottis stenosis or interarytenoid adhesion has sometimes been misdiagnosed as cord paralysis. Laryngoscopy and laryngeal electromyography studies are the two diagnostic aids in this condition. [19]
Other important aspects of the evaluation include assessment of inflammatory changes in the larynx, the size of the airway, and evidence of gastroesophageal reflux (eg, interarytenoid edema, erythema).
Histologic Findings
In rare cases of glottic stenosis caused by a granulomatous or systemic infection or disease, biopsy is necessary to make the diagnosis. The presence or absence of caseous necrosis or vasculitis differentiates tuberculosis, sarcoidosis, and Wegener granulomatosis. Identification of causative organisms can also be accomplished using the biopsy specimen.
Staging
Cohen’s classification is as follows: [20]
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Type I : This is the mildest form of the web. It involves less than 35% of the glottis. It is usually thin and uniform in thickness with no subglottic extension. The true vocal cords are usually well seen through the web. The patient usually has an adequate airway and only slight voice change.
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Type II: The web involves 35-50% of the glottis and can be thin or thick, but the vocal cords can usually be seen within the web. These may be associated with some subglottic extension of stenosis. Patients usually don't have too much airway obstruction or airway symptoms.
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Type III: This type involves 50-75% of the glottis. The web is usually very thick anteriorly and may thin out as it extends posteriorly. The true vocal cords may or may not be visible within the web; these almost always have a subglottic component to them. Patients have marked vocal dysfunction and have moderate-to-severe airway symptoms.
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Type IV: This is the most severe form. The web involves 75-90% or more of the glottis and is uniformly thick both anteriorly and posteriorly. The true vocal cords are not identifiable within the web and may be one continuous, thick band. The patient is usually aphonic. Severe airway obstruction is usually present and almost always requires an emergency tracheotomy.
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Anatomical regions of the larynx.
