Obstructive diseases of the trachea

O b s t r u c t i v e D i s e a s e s of the T r a c h e a Wallace T. Miller, Jr A R G E A I R W A Y S diseases that result in airways obstruction may be divided into three categories of disease: intrinsic tracheal abnormalities, extrinsic compression, or invasion of the trachea by mediastinal lesions and foreign bodies. Intrinsic and extrinsic lesions may be subdivided into malignant and nonmalignant causes. In general, malignant causes are more common among adult patients and nonmalignant causes are more c o m m o n among pediatric patients. 1-4 Many abnormalities may be detected by careful observation of the tracheal air column on the chest radiograph. Computed tomography (CT) will most often provide improved detection and characterization of diseases of the central airways. 5

L

INTRINSIC CAUSES OF CENTRAL AIRWAYS OBSTRUCTION Focal Tracheal Narrowing That May Cause A i r w a y Obstruction Focal tracheal strictures can be subdivided into two general categories of disease: neoplastic causes and non-neoplastic causes. Of strictures of sufficient severity to require surgical reconstruction, malignant lesions have accounted for between 25% and 66% of cases of which one third are primary lesions and two thirds are secondary. 3,4 Secondary lesions are most often caused by direct extension of mediastinal or pulmonary malignancies into the trachea and will be discussed under extrinsic causes of tracheal obstruction. Most benign strictures are caused by post-intubation or post-tracheostomy injuries. Other causes rarely will be discovered.

Tracheal and Central Bronchial Neoplasms Primary tumors of the trachea are quite rare, constituting only 2% of all respiratory tract tumors and are responsible for 0.1% of all cancer deaths.6,7 In two large series of tracheal tumors, one at the M a y o Clinic over 30 years and a second multicenter study from France, 53% and 83% of tumors were malignant, most commonly squamous cell carcinoma and adenoid cystic carcinoma and more rarely carcinoid tumors, mucoepidermoid carcinomas, and a wide variety of carcinomas, sarcomas, lymphomas, and plasmacytomas. 7-9 However, infants and children are more likely to have benign

tracheal tumors, which were seen in 93% of cases reported by Gilbert et al ~ and 64% reported by Desai et al. 2 Most common benign tumors are solitary and multiple papilloma, nerve sheath tumors, and hemangiomas and other vascular tumors or malformations. The most common presenting symptom of patients with intrinsic tracheal tumors is dyspnea at rest or with exertion in approximately 80% of cases. ~~ The tracheal lumen must be narrowed by one third of the normal diameter for symptoms of dyspnea to occur. This airway narrowing may be clinically recognized as stridor, a whistling sound heard on inspiration. This may be confused with wheezing, and therefore it is not uncommon that patients with airway tumors will be treated for asthma for a prolonged period before diagnosis. 7 Cough is also commonly present in patients with tracheal tumors. Hemoptysis m a y be present in as many as 20% of patients. Most of these will have squamous cell carcinoma. Recurrent pneumonia, changes in voice related to invasion o f the recurrent laryngeal nerve, or direct extension into the larynx and dysphagia from invasion of the esophagus are infrequent symptoms encountered in patients with tracheal neoplasms. 7 Benign neoplasms of the trachea. Table 1 outlines the relative frequency of common benign tracheal neoplasms in two large series of tracheal tumors. As noted previously, these are more commonly encountered in children and most often comprise laryngeal papilloma, hemangiomas, pleomorphic adenomas, chondromas, and the nerve sheath tumors: neurofibromas and neurolemmomas. Benign tracheal neoplasms are less common than malignant tracheal neoplasms and account for less than 10% of tumors involving the trachea and mainstem bronchi.1 Papilloma represent a branching or lobulated tumor composed of a fibrovascular stalk and surrounding epithelium. When involving the tracheoFrom the Department of" Radiology, Thomas Jefferson University Hospital, Philadelphia, PA. Address reprint requests to Wallace T. Miller, Jr, MD, Department of Radiology, Suite 3390 Gibbon, Thomas Jefferson Unviersity Hospital, 111 S l r h st, Philadelphia, PA 19107. Copyright 9 2001 by' ~ B . Saunders Company 0037-198X/01/3601-0005535.00/0 doi: 10.1053/groe.2001.20461

Seminars in Roentgenology, Vol XXXVI, No 1 (January), 2001: pp 21-40

21

22

WALLACE T. MILLER, JR

Table 1. Benign Tumors of the Trachea

Tumor Type Squamous papilloma Multiple Solitary Neurogenic t u m o r * Vascular tumor or malformation Pleomorphic adenoma Chondroma Other benign t u m o r Total

Perelman Grillo and Koroleva and Mathisen (1987)6 (1990)16

Total

9 --6 4

5 4 1 6 3

14 (28%)

12 (24%) 7 (14%)

4

2

6 (12%)

-4

2 5

2 (4%) 9 (18%)

27

23

50

*Neurofibroma, neurolemmoma, paraganglioma.

bronchial tree, they come in two clinical and etiologic scenarios: multiple and solitary. The multiple form o f airway papilloma is referred to as juvenile laryngotracheal papillomatosis. This is an uncommon neoplastic growth secondary to infection with human papilloma virus types 6 and 11 but is the most common benign tracheal neoplasm. 6 There is an association with maternal genital warts and the development of laryngeal papillomas in children and therefore this disorder may be transmitted through oropharyngeal aspiration at the time of birth.J2 Most often papilloma will be present in the larynx of infants and young children, and in most cases will remain localized or will spontaneously resolve. 13 Older series have reported an approximately 2% incidence of involvement of the tracheobronchial tree; however, more recent sources suggest that tracheobronchial involvement may occur in as many as 20% of cases, v,~3 Papillomatosis results in multiple polypoid mucosal masses. The pathogenesis of papilloma in the lower respiratory tract is not clear; however, some authors suggest that fragments of the tumor may spread to the more distal airways. ~-~5 Radiographic manifestations include polypoid intraluminal masses, atelectasis, and obstructive pneumonitis. 15 Involvement of distal airways can produce pulmonary nodules, which are frequently cavitary when present. In limited cases, the tumors can be resected using a combination of bronchoscopic excision and ablation of the base of the tumor with a N d : Y A G laser, v However, in more extensive cases, prognosis is poor. L~ Solitary papilloma of the tracheobronchial tree is less common than the multiple form and characteristically occur in middle-aged men. 12 This

differing epidemiology suggests that these tumors may have a different pathogenesis from juvenile laryngotracheal papillomatosis. Solitary papilloma are usually small (5 to 15 m m in diameter), intraluminal masses that most commonly occur in the lobar and segmental bronchi and produce atelectasis and obstructive pneumonitis on chest radiographs. J2 Tracheal locations have been reported. L6 Pleomorphic adenoma is the most common benign bronchial gland tumor to affect the trachea. 6.~6 Although common to the major salivary glands, this is an exceedingly rare tumor of the tracheobronchial tree. It consists of an epithelial component that forms small cystlike or glandlike structures and a myoepithelial component. ~2 When present in the airways, it most often effects the trachea or central airways and produces symptoms o f airways obstruction. Other benign bronchial gland tumors have been reported. ~2 These include actinic cell tumor, oncocytoma, myoepithelioma, and mucous gland adenoma. In general, these are limited to single case reports and are therefore of little general interest. Tumors of nerve origin may be found and are derived from paratracheal neural bundles that travel longitudinally with the trachea. Most commonly, these tumors are neurofibromas and neurolemmomas (schwannomas). They will appear as broad-based, well-defined masses centered on the tracheal wall, an appearance that indicates their origin from submucosal tissue. Endobronchial excision is usually not possible because of the submucosal nature of the tumor and segmental resection of the trachea will usually be necessary to remove the tumor. 7 Rarely, other benign neurogenic tumors have been reported, such as paraganglioma. ~6 Tracheal hemangiomas are encountered in young infants and may increase in size in the first few weeks of life but then spontaneously regress and disappear over the subsequent few years. 17 This pattern parallels that of cutaneous hemangioma. The tumor may arise directly from the tracheal wall or extend into the trachea from a larger mediastinal mass. Many lesions will require no treatment, but in those that produce significant airways obstruction, a tracheostomy may be necessary to provide adequate ventilation. Both radiation therapy and corticosteroids have been used to shrink large symptomatic tumors, v Chondroma is the most common tumor of the

OBSTRUCTIVE DISEASES OF THE TRACHEA

23

mesenchymal tissue of the trachea. '7 As a benign neoplasm, there is a 4:1 male preponderance. Unlike most other benign tumors of the trachea, this is more commonly encountered in adults than children. It will appear as a well-defined polypoid mass extending into the tracheal lumen. It will often have regions of calcification detectable by CT imaging, a potential clue to the diagnosis. The only other tracheal tumors likely to have radiographically identifiable calcification are hamartomas and chondrosarcomas. It is often possible to bronchoscopically remove this tumor. 7 Other benign mesenchymal tumors may be encountered within the trachea. These include fibromas, leiomyomas, lipomas, fibrous histiocytomas, and hamartomas. These are all rare and will appear as round or oval well-defined submucosal masses with projection into the tracheal lumen. When calcification is present, a hamartoma or chondroma may be suggested. In other cases, biopsy will be necessary to determine the histology of the mass. Malignant neoplasms of the trachea. Table 2 outlines the relative frequency of malignant tumors of the trachea. The most common of these are bronchogenic carcinoma; usually squamous cell carcinoma, carcinoid tumors, and malignancies of the bronchial glands; adenoid cystic and mucoepidermoid carcinomas. Rarely, primary tracheal sarcomas, melanomas, and lymphomas may be found. Squamous cell carcinoma is the most common primary malignancy of the trachea derived from the tracheal epithelium and accounts for approximately 50% of all tracheal tumors (Fig 1). 9'10'16'18 These tumors may be more common in the distal one third of the trachea. 7 Other bronchogenic carcinomas, including adenocarcinoma, small cell

carcinoma, and adenosquamous carcinoma, have been reported to arise from the tracheal epithelium. However, in practice, this is exceedingly uncommon as they accounted for only 5% of tracheal malignancies in four large series of tracheal malignancies. 9,1~ Most patients with squamous cell carcinoma and other epithelial neoplasms of the trachea will have an extensive smoking history. Direct extension of tumor into the mediastinal soft tissues has been found in approximately one third of patients, and cervical lymph-node metastasis has been found in approximately one third of patients. '7 Survival is poor despite surgical and radiation therapy. Perelman and Koroleva6 in a 1987 report, demonstrated 27% 3-year survival and 13% 5-year survival. In a study completed in 1996, Regnard et al 9 reported a 47% 5-year survival and a 36% 10-year survival. Adenoidcystic and mucoepidermoid carcinomas are low-grade malignant neoplasms of the minor salivary glands and mucous-secreting cells of the major airways.t2 Adenoidcystic carcinomas are the second most common tumor of the trachea and account for approximately one third of all tracheal malignancies, and in some series are more prevalent than squamous cell carcinoma (Fig 2). 9'10'16'18 Approximately 40% of adenoidcystic carcinomas will arise from the trachea, and another 40% will be found in the mainstem bronchi.19 In the past this has been call a "cylindroma." This terminology is discouraged because it implies that the tumor is benign. When they involve the major airways, adenoid cystic carcinoma most often presents with lobar atelectasis. When involving the trachea, they will often present with dyspnea and obstructive physiology. They are usually first recognized in

Table 2. Malignant Tumors of the Trachea Tumor Type

Grillo and Mathisen (1990)16

Gelder and Hetzel (1993) 18

Regnard et a[ (1996)l~

Total

19969 Bronchogenic carcinoma S q u a m o u s cell carcinoma Adenocarcinoma Small cell carcinoma A d e n o s q u a m o u s carcinoma

70 1 1 1

174 13 16

21 1 3

94 4 --

359 (48%) 19 (3%) 20 (3%)

80 4

34 --

66 1

65 5

245 (33%) 10 (1%)

11 5

1 34

20 9

9 4

41 (5%) 52 (7%)

173

272

121

181

Perelman

(0.1%) Bronchial gland carcinoma A d e n o i d cystic carcinoma M u c o e p i d e r m o i d carcinoma Other m a l i g n a n c y Carcinoid t u m o r s Other malignancy Total

747

24

WALLACE T. MILLER, JR

Fig 1. Squamous cell carcinoma of the trachea. (A) Magnified view of the superior mediastinum on the PA radiograph shows an apparent gap (arrows) in the tracheal air column at the level of the third thoracic vertebra. (B) Lateral radiograph reveals a subtle middle mediastinal mass involving the posterior wall of the trachea (arrows). These findings are often the only plain film clues to the diagnosis of a tracheal neoplasm. This man w h o complained of dyspnea and hemoptysis underw e n t an MRI examination of the thorax. (C) Sagittal image through the trachea confirms the presence of a rounded mass (arrow) centered on the posterior tracheal wall. Histologic evaluation of the bronchoscopic biopsy diagnosed a squamous cell carcinoma, the most common malignant t u m o r of the trachea.

patients in their 40s, without sex predominance. 12,19,2~Although some chest radiographs and conventional tomograms may demonstrate a hemispheric or lobulated mass projecting into the lumen of the trachea or main bronchi, CT scans or magnetic resonance imaging (MRI) examinations will reveal that there is nearly always extension of tumor into the surrounding mediastinal soft tissues. 21.22 Adenoidcystic carcinoma has a predilec-

tion for longitudinal spread along the nerve sheaths traveling underneath the tracheal cartilage rings, v,~9 Thus, tumor may appear as a focal mass with extensive longitudinal thickening of the tracheal wall and is an important imaging clue to the diagnosis of adenoidcystic carcinoma (Fig 2). It is important for the radiologist to recognize this longitudinal extension, which may be unrecognized or underestimated on CT scans. It is also

OBSTRUCTIVE DISEASES OF THE TRACHEA

25

Fig 2. Adenoid cystic carcinoma of the trachea. This 53-yearold man complained of dyspnea, hemoptysis, and cough. Axial images of an MRI examination at the level of the (A) aortic arch, (B) AP w i n d o w , and (C) carina demonstrate asymmetric thickening (arrows) of the walls of the trachea and left mainstem bronchus, At the level of the AP w i n d o w , this thickening expands into a fusiform mass along the left tracheal wall, which narrows the tracheal lumen. The extensive submucosal spread of tumor is characteristic of adenoid cystic carcinoma, which was subsequently proven at biopsy of the mass. This longitudinal extension of t u m o r often makes complete surgical resection of adenoid cystic carcinoma impossible. It is important for radiologists to recognize this tendency of adenoid cystic carcinoma, both to correctly diagnose the t u m o r and also to alert the surgeon to the longitudinal extent of tumor.

important to alert the surgeon to the extension of tumor that is a significant problem for surgical therapy because it may require a more extensive resection of the trachea than is technically feasible. 7 Local recurrence is a common phenomenon with this tumor, and therefore, careful surveillance by CT or MRI for recurrent soft-tissue masses is indicated. Fortunately, even with incomplete resection of the tumor, patients may have an extended survival, and one series showed no survival difference between those patients with complete surgical resection and those with microscopically positive margins. 9 In two large reports of surgery for adenoidcystic carcinoma, 5-year survival rates ranged from 66% to 73%, and 10-year survival rates ranged from 56% to 57% of patients. 9,16 Metastasis are uncommon and most often appear late in the course of disease. Death is usually a result of local intrathoracic complications, z~ Mucoepidermoid carcinoma is less common than adenoid cystic carcinoma and represents ap-

proximately 1% of tracheal malignancies.9.1 o,16.18 Most mucoepidermoid carcinomas arise in the main and lobar bronchi with a small minority originating in the trachea, z3 Characteristically, the tumor will be discovered in young and middleaged adults, usually in their 30s and 40s. 24 Patients will present with symptoms related to intralumina growth of the tumor, such as cough, hemoptysis, wheeze, and recurrent pneumonia. Unlike adenoidcystic carcinomas, the tumor is usually confined to the bronchial wall and does not spread into adjacent pulmonary or mediastinal tissues. Most tumors can be completely resected for cure. 24 In a series from the Air Forces Institute of Pathology (AFIP), 41 cases presented as a solitary pulmonary nodule and 16 as atelecatsis or post-obstructive pneumonitis. 24 Carcinoid tumor, a neuroendocrine carcinoma, is derived from Kutchitzky cells, part o f the epithelium of the central airways. These most often, approximately 80% of the time, involve the central

26

bronchi and present with lobar atelectasis or hemoptysis. In a few percent of cases, pulmonary carcinoids will present with symptoms of specific hormone secretion, such as Carcinoid syndrome, Cushing's syndrome, acromegaly, Zollinger-Ellison syndrome, or hyperinsulinemia. 25 Carcinoid tumors account for 0.6% to 2.4% of all pulmonary neoplasms. 26-29 There appears to be a slight female predominance and are seen with greater frequency in Caucasians than in African Americans. 26-29 They are the third most common tracheal carcinoma and may account for as many as 5% of tracheal malignancies. 9.1~176 When this occurs, they may result in proximal airway obstruction with the usual symptoms of tracheal masses, such as dyspnea, cough, and wheezing or stridor. On bronchoscopic evaluation, carcinoid tumors have a characteristic cherry red appearance because of their extensive vascular supply, and as a result, they are prone to extensive bleeding when undergoing biopsy. Carcinoid tumors have a variable malignant potential. This risk of metastasis can be estimated by pathologists based on the extent of mitosis, nuclear and cellular pleomorphism of the tumor, and presence of necrosis. 25 Those tumors with low mitotic rate and a bland, monomorphic appearance are referred to as typical carcinoids, very rarely metastasize, and are often cured with a limited surgical resection. Those tumors with nuclear pleomorphism, a high mitotic rate, and presence of necrosis are referred to as atypical carcinoids and have a significant rate of metastasis, as much as 70% of cases, and a correspondingly worse prognosis. 25 The presence of lymph-node metastasis indicates a bad prognosis and therefore requires more extensive surgical resection. 7.31 Atypical carcinoid tumors account for approximately 10% of all carcinoids. 25 When involving the central bronchi, carcinoid tumors will most often present as lobar or segmental atelectasis. Segmental atelectasis may show periodic exacerbations and remissions. ~2 When peripheral, it may appear as a solitary pulmonary nodule. When involving the trachea it will appear as a smooth, well-defined sessile mass projecting into the lumen of the trachea. Gross pathologists have noted that in most carcinoids, most of the tumor is extraluminal, with only a small portion projecting into the lumen of the a i r w a y - - a manifestation that has resulted in the term "iceberg tumor. ''~2 Tracheal malignancies other than bronchogenic

WALLACE T. MILLER, JR

carcinoma, adenoidcystic carcinoma, mucoepidermoid carcinoma, and carcinoid tumor account for approximately 8% of all tracheal tumors. 9,1~ These include soft-tissue sarcomas, such as chondrosarcomas, fibrosarcomas, and rhabdomyosarcomas. These are derived from the soft-tissue elements of the tracheal wall and are exceedingly rare. Tracheal melanomas have also been reported as have primary tracheal lymphomas and plasmacytomas. 7 Hematogenous metastasis to the trachea is exceedingly rare. The most likely source of hematogenous metastasis to the trachea are melanomas, breast carcinomas, and malignancies of the genitourinary tract. ~ These will most often appear as a polypoid soft-tissue mass projecting into the tracheal lumen. Post-lntubation or Post-Tracheostomy Stricture

Tracheal stenosis as a complication of intubation or tracheostomy is one o f the most common causes o f chronic upper airway obstruction. 32 In one series o f 342 patients who had received prolonged endotracheal intubation, 5% manifest stridor at the time of extubation and 1% of patients developed fibrotic stricture. 33 Many of these post-intubation strictures will be roentgenographically visible and yet will be clinically insignificant. In two studies of clinically significant strictures resulting from prior tracheostomies, strictures were found both at the site of the stoma and also at the location of the inflatable cuff. 34,35 Other experts also implicate the tip of the tube as a potential cause of stricture. 36 Experimental studies with dogs have found that increasing the size of the tracheostomy and increasing the inflating pressure of the balloon independently increased the severity of resultant strictures. 37 At the stoma, strictures may preferentially affect the anterior surface of the trachea. In cross section, the trachea resembles a peaked roof or A-shaped stricture. 36 The endotracheal or tracheostomy balloon may cause circumferential erosion of the tracheal mucosa, which can result in circumferential narrowing of the trachea. In other instances, a thin membrane or polypoid granuloma may form as a result of irritation of the tracheal mucosa. 36,38,39 One author believes this to be most commonly a manifestation of erosion by the endotracheal tube tip. 36 Granuloma formation appears especially prone to occur in children where tubes without balloons are frequently used. Grillo, 36 a surgical expert in the reconstruction of tracheal

OBSTRUCTIVE DISEASES OF THE TRACHEA

stenosis, suggests that this propensity in children may be due the tendency to use endotracheal tubes without cuffs where the tube tip may be more free to locally erode the trachea. Tracheomalacia and airway obstruction due to tracheal collapse may also result from prolonged intubation. 36,4~ Strictures following tracheal resection is an uncommon cause of tracheal stenosis. It is especially prone to occur following carinal reconstructions due to the complexity of the repair. 36 It also occurs with greater frequency the greater the length of tracheal resection and the greater the circumferential peritracheal dissection.

Strictures Due to Inhalational Burns Thermal injury to the tracheal mucosa is a rare cause of tracheal fibrosis. Five percent to 3 1% of cases of severe burn injuries requiring hospitalization will result in thermal injury to the central airways; however, only 0.4% of burn victims will develop clinically significant post-burn stenosis. 41,42 Inhalational burns are most frequently seen in those with facial burns and those with extensive burns to the body. Characteristically, the extent of tissue damage is most severe in the proximal trachea just below the vocal cords and progressively decreases in the more distal trachea. Gaissert et a143 noted that of 18 patients treated for tracheal injuries due to bums, 14 had subglottic strictures as the primary site of injury. In one series of 1,878 bum victims, 7 cases of stenosis developed within 1 to 22 months following the injury. 4z

Laryngotracheobronchitis (Croup) Laryngotracheobronchitis, more commonly known as croup, is an acute viral respiratory illness commonly seen in young children, usually less than 4 years of age. 44 This is the most common cause of acute obstructive airways disease in children. 45,46 Viral infections known to cause croup in order of frequency are as follows: parainfluenza virus, respiratory syncytial virus (RSV), adenovirus, influenza A and B viruses. These organisms produce mucosal and submucosal edema throughout the tracheobronchial tree. However, the mucosa approximately 1 cm below the larynx is only loosely attached predisposing this site to critical narrowing due to edema. The complete ring of the cricoid cartilages also accentuates this predisposition to airways obstruction. This edema results in the loss of the normal lateral convexities of the subglottic

27

trachea and results in the characteristic inverted "V" appearance of the proximal trachea as seen on frontal chest and neck radiographs. 45 Typically, patients will present with stridor and a barking cough after several days of fever and rhinitis.

Idiopathic Subglottic Stenosis In rare instances, a short segment stenosis of the trachea may be found without antecedant history of trauma, infection, inhalation injury, intubation, or systemic disorder known to produce tracheal stenosis. 47 This characteristically occurs in women who present with progressive dyspnea on exertion and wheezing. The stenosis is most often 2 to 3 cm in length and present in the proximal trachea, just distal to the larynx. Circumferential fibrosis is present without destruction of the tracheal cartilages. Radiographs may demonstrate a focal area of narrowing in the cervical trachea. CT will confirm the stenosis and may demonstrate focal wall thickening (Fig 3).

Diffuse Tracheal Wall Abnormalities That May Cause Airway Obstruction Diffuse disorders of the trachea are rare phenomena. However, these are important entities for radiologists to be aware of because CT scanning can play an important role in their diagnosis. These disorders produce obstructive lung disease, in most cases because they result in diffuse narrowing of the trachea, or because the airway wall collapses during inspiration. They fall into several classes of disease: (1) tracheomalacia; (2) systemic inflammatory conditions, which may affect the trachea such as relapsing polychondritis, Wegener's granulomatosis, and Crohn's disease; (3) infiltrative disease, which may affect the trachea such as amyloidosis; and (4) idiopathic abnormalities of the tracheal wall, such as tracheopathia osteochondroplastica and tracheomegaly (Mune Kuhns disease). The CT appearance of these diseases are in some ways different from one another and may help in distinguishing between the various causes of diffuse tracheal narrowing. Each entity will be reviewed and their salient CT features are outlined in Table 3.

Tracheomalacia and Bronchomalacia Tracheomalacia and bronchomalacia are descriptive terms indicating weakness of the walls of the trachea and bronchi and their supporting structures. 1~ There is a rare congenital form of the

28

WALLACE T. MILLER, JR

cheal collapse during inspiration. The most common cause of tracheomalacia is extended endotracheal intubation or tracheostomy. However, chronic obstructive pulmonary disease, trauma, recurrent infection, and polychondritis are other potential causes. Chest radiographs may demonstrate narrowing of the trachea, which may be focal or diffuse. CT will confirm the luminal narrowing and will show the tracheal wall to have normal or near normal thickness (Fig 4). 11'48 Greater than 50% collapse of the trachea on expiratory images in comparison to inspiratory images has been promoted as an indicator of tracheomalacia on CT scans. 49

Relapsing Polychondritis

Fig 3. Idiopathic subglottic stenosis. Complaints of dyspnea and wheezing brought this 61-year-old woman to medical attention. A t first inspection, the chest radiograph appeared normal. (A) However, more careful observation demonstrated the tight cervical tracheal stricture (arrow) demonstrated in this magnified image of the thoracic inlet. (B) Axial CT image through the cervical trachea at the level of the thyroid gland reveals eccentric thickening of the tracheal wall (arrows) with resultant narrowing of the lumen. This appearance is quite suggestive of a tracheal neoplasm; however, histologic evaluation of the surgical specimen demonstrated fibrosis without evidence of neoplasm. Focal benign strictures at this location will most often be secondary to prior intubation, tracheostomy, or other traumatic event. However, this patient had no history of antecedent conditions associated with tracheal stenosis. Idiopathic subglottic stenosis has been reported to be most commonly seen in elderly women similar to this patient.

disease due to deficiency of cartilage. However, most cases are a result of degeneration of the tracheal cartilages due to chronic inflammation. The loss of cartilaginous integrity results in tra-

Relapsing polychondritis is an idiopathic autoimmune inflammatory condition of cartilage, which results in destruction of cartilaginous structures throughout the body, most commonly the ear lobes and the nose but also including the, fibs, tracheobronchial tree, and peripheral joints. 48,5~ The diagnosis is made on the basis of recurrent inflammation of two or more cartilaginous sites. Some of the more prominent abnormalities include tracheal collapse, deformity and flaccidity of the nose and ears, and joint and anterior rib pain. Chondrolysis can lead to severe arthritis. In addition to manifestations of chondritis, other findings include cataracts, episcleritis, iritis, hearing impairment, anemia, myocarditis, aortic valvular insufficiency, and liver function abnormalities. 5~ Chest radiographs may demonstrate narrowing of the trachea. Involvement of the tracheal and bronchial cartilages is one of the most serious clinical manifestations of relapsing polychondritis. Respiratory complications have accounted for 50% of reported deaths. 5~ Fixed narrowing of the trachea and central bronchi may be demonstrated on chest radiographs but will be demonstrated to better advantage on CT or MRI. lk48,52 CT will confirm the airway narrowing and will demonstrate extensive thickening of the tracheal wall without calcification (Fig 5). jl,48 The absence of calcification is an important diagnostic feature separating relapsing polychondritis from some other diffuse tracheal disorders that can be recognized on imaging.

Wegener's Granulomatosis Wegener's granulomatosis is an autoimmune granulomatous vasculitis with predilection for involvement of the lungs, kidneys, and upper and

OBSTRUCTIVE DISEASES OF THE TRACHEA

29

Table 3. Diffuse Disorders of t h e Tracheal Wall Disease

Tracheomalacia Relapsing polychondritis Wegener's g r a n u l o m a t o s i s Crohn's disease Amyloidosis Tracheopathia osteochondroplastica Tracheomegaly

Caliber decrease decrease decrease decrease decrease decrease increase

lower respiratory tract. Prevalence in the United States has been estimated to be approximately 3 per 100,000 individualsP 3 It typically affects patients in their 30s to 50s and is without sex predominance. The cause remains uncertain. Thoracic involvement most commonly appears as one

Wall Thickness

Ca++

Extrathoracic Findings

+ + + + + -

-

++ + ++ +++ + +

+ + + + +

+ + + + +

++ +++ -

or multiple pulmonary nodules or as diffuse alveolar hemorrhage. Tracheobronchial involvement is uncommon and when present is usually a late manifestation of disease. However, tracheal narrowing m a y rarely be the presenting complaint. 54 Pathologically, there is granulomatous inflamma-

B J

Fig 4. Tracheomalacia. This 36-year-old m a n had previously received a cadaveric renal transplant. A l t h o u g h t h e t r a n s p l a n t w a s f u n c t i o n i n g w e l l , t h e p a t i e n t c o m p l a i n e d of difficulty breathing. Serial chest radiographs (not s h o w n ) d e m o n s t r a t e d a persistent left l o w e r lobe opacity t h o u g h t t o be atelectasis. (A) Lateral chest radiograph s h o w s m a r k e d n a r r o w i n g o f t h e trachea (arrows). (B and C) CT i m a g e at t h e level of t h e great vessels c o n f i r m s collapse o f t h e trachea (arrow) w i t h o u t evidence o f w a l l thickening. This appearance is characteristic o f tracheomalacia. A l t h o u g h there is no d e f i n i t i v e proof, t h e tracheomalacia is likely a c o m p l i c a t i o n o f p r i o r i n t u b a t i o n .

30

WALLACE T. MILLER, JR

!

Fig 5. Relapsing polychondritis. This 41-year-old woman had incorrectly been diagnosed with asthma for the preceding 2 years. (A) Magnified view of the superior mediastinum shows diffuse irregular narrowing of the entire extent of the trachea (arrows). Axial CT images at the level of the (B) aortic arch and (C) carina demonstrate luminal narrowing as well as extensive thickening of the tracheal wall. The long extent of this stenosis suggests one of the diffuse tracheal wall abnormalities. The absence of calcification makes relapsing polychondritis and Wegener's granulomatosis among the more likely diagnoses. Note the sparing of the posterior wall oft the trachea in image B. The membranous trachea has no cartilages and therefore is spared the inflammatory response in patients with relapsing polychondritis, which was the final diagnosis in this patient.

tion and vasculitis involving the mucosa and submucosa of the airway. Chest radiographs and CT may demonstrate segmental, lobar, or total lung collapse. 55 It will often be difficult to recognize the tracheobronchial involvement by chest radiographs, although focal and diffuse tracheal narrowing may be demonstrated. Tracheal and bronchial wall thickening and luminal narrowing will often

be detected by CT. 11,54,56-58 The most common location to detect tracheobronchial involvement is the subglottic trachea. Ulcerative Colitis Although exceedingly rare, tracheobronchitis is one of the many extraintestinal manifestations of ulcerative colitis. Airway disease may predominantly

OBSTRUCTIVE DISEASES OF THE TRACHEA

involve the large airways and produce diffuse irregular narrowing and bronchiectasis or predominantly small airway narrowing and result in bronchiolitis obliterans. 59 CT scans may demonstrate diffuse irregular thickening of the tracheal wall without calcification, which results in diffuse luminal narrowing.l~

Amyloidosis Amyloidosis, a disorder of abnormal protein deposition, may have wide ranging systemic effects in nearly all organ systems including renal disease, CNS vascular disorders, bone lesions, and pulmonary masses. Amyloidosis has traditionally been classified into four major forms.~~ In primary amyloidosis, there is either an underlying plasma cell disorder, such as multiple myeloma, or there is no recognizable associated disorder. In secondary amyloidosis, there is an identifiable underlying chronic inflammatory disorder, such as tuberculosis, bronchiectasis, syphilis, autoimmune diseases such as rheumatoid arthritis, Crohn's disease, and ulcerative colitis or neoplasms, such as Hodgkin's lymphoma and renal cell carcinoma. Hereditary forms of the disorder are classified as familial amyloidosis. Finally, senile amyIoidosis describes the idiopathic form seen in elderly individuals, most commonly those over 70 years old. Thoracic involvement by amyloidosis may take one of several anatomic patterns of involvement: (1) tracheobronchial, (2) nodular parenchymal, and (3) diffuse interstitial forms. Although these anatomic patterns may overlap, in most cases, there is a predominant site of involvement. 6~ Tracheal involvement is exceedingly rare and may be associated with other systemic findings or may be the only organ involved. 48 Tracheobronchial involvement most commonly results in diffuse or multifocal submucosal infiltrates that produce apparent tracheal wall thickening and tracheal narrowing. 11'48'62 Less commonly it will produce a single submucosal masslike lesion. Calcification or ossification may occur, although it is less common than calcification in tracheopathia osteochondroplastica. Chest radiographs and CT scans will demonstrate luminal narrowing of the trachea and mainstem bronchi. CT will also demonstrate the thickened tracheal wall and areas of submucosal calcification.

Tracheobronchopathia Osteochondroplastica Tracheobronchopathia osteochondroplastica is a rare idiopathic disorder of the trachea resulting in

31

bony metaplasia of the submucosal tissues of the trachea. 63 This disorder is most commonly seen in elderly men and may often be clinically silent, only to be discovered at autopsy. Patients may occasionally complain of dyspnea, hoarseness, cough, wheezing, or hemoptysis. 64 The bony metaplasia is virtually always confined to the tissues adjacent to the tracheal cartilages, leaving the membranous trachea normal. Bronchoscopic evaluation will show small white protuberances, which are shown to be very hard by their unyielding character as the bronchoscope bounces off them. Radiographic abnormalities are confined to the trachea and proximal bronchi, which demonstrate diffuse luminal narrowing that may have a nodular character. 4s,63 Chest radiographs may rarely demonstrate focal areas of calcification, a finding that should strongly suggest tracheobronchopathia osteochondroplastica. CT will also reveal diffuse narrowing and will easily demonstrate calcified nodules that protrude into the t r a c h e a l l u m e n . 48,65,66 CT will also demonstrate wall thickening adjacent to the cartilages with sparing of the membranous portion of the trachea (Fig 6).

Tracheobronchomegaly Tracheobronchomegaly, or Mounier-Kuhns syndrome, is the only diffuse abnormality of the trachea resulting in increased luminal diameter. This condition is of unknown pathogenesis. Pathologically, both the cartilaginous and membranous portions of the trachea are affected with resultant thin, atrophied muscular and elastic tissues. 67,68 This causes increased compliance of the central airways resulting in abnormal flaccidity and easy collapsibility of the central airways, which may be directly visualized bronchoscopically. Pulmonary function tests will show an obstructive pattern of abnormality with decreased flow rates and increased dead space. The disease is reported to predominantly affect males. 69 Patients may develop dyspnea because the abnormal increased compliance of the trachea prevents normal efficient transfer of air. Patients will characteristically have a cough with a whooping sound, which is caused by motion of the floppy trachea. Patients may also develop recurrent pneumonias as a result of impaired cough mechanics. In normal individuals the diameter of the central airways progressively decreases from proximal to distal airway resulting in

32

WALLACE T. MILLER, JR

,q

Fig 6. Tracheobronchiopathia osteochondroplastica. Following several years of persistent cough and dyspnea, this 53-year-old woman was clinically evaluated. (A) Magnified view of the mediastinum on a PA chest radiograph demonstrates severe diffuse narrowing of the trachea and mainstem bronchi (arrows). CT images at the (B) aortic arch and (C) carina reveal irregular narrowing of the trachea and mainstem bronchi and thickening of the tracheal wall. The CT images also show large irregular calcifications in the wall of the trachea (arrows), a feature characteristic of tracheobronchiopathia osteochondroplastica.

increased linear velocity of expired air, leading to efficient transfer of mucous. In tracheobronchomegaly, the bronchi do not uniformly decrease in diameter and they and the trachea may transiently collapse, features that impair efficient transfer of mucous and can lead to mucous retention and airway infection. 32 Chest radiographs will show marked dilatation of the sagittal and coronal diameters of the trachea. Careful inspection will also show a corrugated appearance of the anterior trachea due to redundant mucosa protruding between the cartilaginous rings. 69 v2 This appearance is often best appreciated on the lateral view. CT will

confirm dilatation of the trachea and will usually show central bronchial dilatation or bronchiectasis (Fig 7). 48,72-74 Airway wall thickness is usually normal. EXTRINSIC CAUSES OF CENTRAL AIRWAY OBSTRUCTION

The most common cause of extrinsic tracheal compression is mediastinal and pulmonary neoplasms. In children, vascular anomalies, such as double aortic arch, may lead to airway compromise. Rarely, mediastinal infections and other disorders will result in tracheal narrowing. These will be reviewed sequentially.

OBSTRUCTIVE DISEASES OF THE TRACHEA

33

Fig 7. Tracheobronchomegaly. This 63-year-old woman suffered from repeated episodes of pneumonia. A t the time of physical examination, a cough with a whooping character was noted, which the patient reported had been present chronically. (A) PA and (B) lateral chest radiographs show marked dilatation of the trachea (arrows). The lateral chest radiograph also demonstrates a serrated appearance to the anterior wall of the trachea (arrows). This combination of findings should raise suspicions of tracheobronchomegaly. Axial CT images at (C) the level of the great vessels and (D) the carina confirm the massive enlargement of the trachea (straight arrow) and main bronchi and also demonstrate central cystic bronchiectasis (curved arrows), findings characteristic of tracheobronchomegaly.

Nontracheal Neoplasms That May Cause Tracheal Obstruction The most common extrinsic mass to narrow the trachea and result in upper airway obstruction is the multinodular goiter. A common benign hyper-

plasia of the thyroid gland related to iodine deficiency, most of these masses have little or no clinical significance. These masses will often displace the trachea rather than narrow it. Most often when there is narrowing, the patient has accommo-

34

dated to the disorder and has no clinical symptoms. Therefore, morphologic narrowing of the trachea by a multinodular goiter, except in extreme cases, should not raise alarm unless it is associated with significant clinical symptoms and physiologic (ie, PFF) evidence of upper airway obstruction. Hodgkin's and non-Hodgkin's lymphomas may, when large, may compress and narrow the trachea and produce respiratory impairment due to obstruction (Fig 8). Thyroid, esophageal, and bronchogenic carcinoma may invade the trachea and produce respiratory obstruction, but this is an uncommon manifestation of these common tumors. With macroscopic invasion, imaging will demonstrate a large extrinsic mass originating in the thyroid, lung, or esophagus, adjacent to the trachea with direct extension of tumor through the tracheal wall and into the tracheal lumen (Fig 9). This is most problematic in the case of esophageal carcinoma because of the incidence of tracheoesophageal fistulae, a complication that may lead to repeated aspiration of esophageal and gastric contents. In some instances, radiation therapy will sterilize a previous esophageal mass, resulting in a new tracheoesophageal fistula.

Extrinsic Compression by Vascular Rings Vascular tings are an important cause of obstructive airways disease in children. In general, the ring must effectively encircle the trachea, or

Fig 8. Hodgkin's lymphoma. This 1g-year-old man with confirmed Hodgkin's lymphoma developed respiratory failure requiring mechanical ventilation despite an absence of pulmonary findings on chest radiograph (not shown). Axial image at the level of the great vessels demonstrates compression of the trachea by a large mediastinal mass. The trachea is stented open by an endotracheal tube (curved arrow) but is otherwise completely collapsed (straight arrow) by the mediastinal mass. Chemotherapy for Hodgkin's disease resulted in regression of the mediastinal mass and restoration of a patent airway, allowing for extubation of the patient.

WALLACE T. MILLER, JR

Fig 9. Esophageal carcinoma. This 68-year-old man complained of dyspnea and dysphagia. Axial image through the superior mediastinum demonstrates a large esophageal mass (white arrows) compressing and deviating the trachea (black arrows) to the right. A left pleural effusion is also present.

trachea and esophagus, to produce sufficient constriction to cause symptoms. Symptoms include respiratory compromise, stridor, or recurrent pneumonia, or symptoms of esophageal obstruction, dysphagia, regurgitation, or poor feeding. 75,76 The vascular rings most likely to cause airways obstruction are as follows: double aortic arch, right arch with an aberrant left subclavian, and pulmonary sling. At Children's Memorial Hospital in Chicago double aortic arch accounted for 92 of 304 (30%) surgical interventions for vascular causes of obstruction over a 50-year period. 75 Right arch with an abberant left subclavian accounted for and additional 81 of 304 (27%) surgical interventions and pulmonary artery sling for 34 of 304 (11%) surgical interventions. Innominate artery compression of the trachea is another vascular cause of tracheal obstruction; however, it is not a vascular ring. Innominate artery compression was the cause of airway compression in 82 of 304 (27%) surgical interventions for tracheal obstruction by a vascular cause in the Children's Memorial Hospital experience. 7s Double aortic arch, as the name implies, represents failure of involution of the embryologic right aortic arch. Thus, the ascending aorta anteriorly divides into two arches, which then coalesce into the descending aorta posteriorly. The trachea and esophagus travel through this complete vascular ring, which can constrict the trachea and esophagus and produce obstruction. In patients with a right aortic arch, an aberrant left subclavian may arise from the descending aorta and ascends to the left arm behind the trachea and esophagus. The ring is completed by the ligamentum arteriosum, which connects the left subclavian artery with the pulmonary artery. Once

OBSTRUCTIVE DISEASES OF THE TRACHEA

35

again, the ring surrounds and can constrict the aorta and esophagus. An aberrant left subclavian artery often has a short segment of aneurysmal dilatation near its origin at the descending aorta. This is known as a diverticulum of Kommerell, and its presence is associated with a higher frequency of airway obstruction. 77 Mirror image arches will most often have a right ligamentum arteriosum and therefore do not constitute a vascular ring. However, in rare cases there may be a right ligamentum arteriosum, which completes the vascular ring and can lead to tracheal or esophageal compromise and clinical symptoms. Pulmonary sling occurs when the left pulmonary artery arises aberrantly from the fight pulmonary artery and travels back to the left lung between the esophagus and trachea. Thus, the right and left pulmonary arteries encircle the trachea and can result in respiratory obstruction. Many infants with pulmonary sling will also have complete tracheal rings. 78 In this entity, the tracheal rings are circular rather than "U" shaped and completely surround the trachea. This may result in a congenital tracheal stenosis. This combination of a pulmonary sling and complete tracheal rings has been called the "ring-sling" complex by Berdon et al. 79 Double aortic arch and aberrant left subclavian may produce a posterior indentation on the trachea, on lateral chest radiographs, and will characteristically produce a posterior indentation on the esophagus following barium swallow (Fig 10). Pulmonary sling will cause a posterior impression on the trachea on chest radiographs and barium swallows and an anterior impression on the esophagus on barium swallows. 8~ MRI and CT scans will directly demonstrate the aberrant vessels (Fig 10).8o-s2 In one retrospective study of symptomatic vascular rings, all 41 cases had one or more radiographic abnormalities on either the PA or lateral chest radiograph, which are associated with congenital vascular rings, s3 Of these 41 case, 18 were double aortic arches, 22 were right aortic arches with an aberrant left subclavian, and 3 were fight aortic arches with mirror image branching but with a left ductus arteriosus. Findings on the lateral radiograph included retrotracheal opacity (79%), anterior bowing of the trachea (92%), and tracheal narrowing (77%). Findings on the PA radiograph included fight aortic arch (85%), distal tracheal indentation (73%), and fight descending aorta (66%). Recognition of these findings in a child

Fig 10. Double aortic arch. A barium swallow and MRI examinations were performed on this 6-year-old girl to evaluate for cough, stridor, and recurrent pneumonias. (A) A lateral view of the barium swallow demonstrates posterior impression (arrow) on the thoracic esophagus and trachea. This is the characteristic appearance of a vascular ring, most commonly a double aortic arch or right arch with an aberrant left subclavian artery. (B) Tl-weighted axial MRI demonstrates compression of the trachea (small black arrow) by a vascular ring (white arrows). Although apparently incomplete on this single image, the complete imaging sequence showed this to be a double aortic arch, which was confirmed at surgery.

with stridor, recurrent pneumonia, or dysphagia should prompt further evaluation with barium swallow CT or MRI to confirm the presence of a vascular ring.

36

WALLACE T. MILLER, JR

Mediastinal Infections That Produce Large Airway Stenosis Granulomatous infection of the mediastinum may result in fibrosis that narrows the airways, which is most dramatic in cases of fibrosing mediastinitis. Fibrosing or sclerosing mediastinitis is a rare condition characterized by progressive mediastinal fibrosis with compression and often constriction of a variety of mediastinal structures including the pulmonary arteries and veins, the superior vena cava, the esophagus, and the central airways. Fibrosing mediastinitis is most often the longterm complication of previous histoplasma infection. For unclear reasons, in some individuals, there is an excessive production of fibrous tissue, which can produce stenosis and occlusion of mediastinal structures decades after the initial infection. An idiosyncratic hypersensitivity reaction to the presence of organisms or associated degenerated materials is the most commonly suggested mechanism for this disorder. 84 Rarely, other organisms have been implicated as the cause including Mycobacterium tuberculosis, Aspergillus species, and Phycomycetes. 84-86 In some cases, no infectious cause can be elucidated. In some instances, the lack of a cause may be due to the difficulty in identifying the organism years after prior infection. However, other instances may be noninfectious in origin. Fibrosing mediastinitis has been associated with idiopathic retroperitoneal fibrosis, orbital pseudotumor, and a variety of other sclerosing lesions. 85 This association suggests that other noninfectious, systemic causes may account for some cases of fibrosing mediastinitis. The most common chest radiographic manifestation is superior mediastinal widening, often with a lobulated appearance, resembling extensive mediastinal adenopathy (Fig 11). 87,88 Calcification within the mass may be radiographically apparent in some cases. In some cases, the mediastinum may appear normal, but secondary effects on the lung implicate the presence of mediastinal disease. These include pulmonary edema due to pulmonary venous obstruction, pulmonary infarction due to pulmonary arterial or venous obstruction, and atelectasis due to airways obstruction. 85 The characteristic CT appearance of fibrosing mediastinitis is of an infiltrating calcified mediastinal mass, a mass being present in 100% of cases, and calcification in 86% of cases in one series of seven patients (Fig 12). 89 This calcification char-

Fig 11. Sclerosing mediastinitis. This 33-year-old resident of Ohio presented with superior vena cava syndrome. PA chest radiograph demonstrates irregular widening (arrows) of the mediastinum, iediastinal biopsy confirmed the presence of sclerosing mediastinitis.

acteristically appears as ill-defined sheets, rather than the globular calcification seen more commonly in lymph nodes from prior granulomatous infection. Narrowing of the tracheaobronchial tree and pulmonary infiltrates were also frequent findings. Other granulomatous infections, which involve mediastinal lymph nodes, may produce tracheobronchial strictures, most commonly tuberculosis. These can produce focal tracheal narrowing and result in respiratory impairment. Surgical resection and laser therapy may be used to correct airway narrowing. 9~

Other Causes of Extrinsic Tracheal Compression Rarely, abnormal thoracic configuration may result in central airways obstruction in children. 9~ Most often this is due to an abnormally narrow anteroposterior dimension with compression of either the trachea at the level of the thoracic inlet or compression of the left mainstem bronchus. Underlying clinical conditions include Marfan's syndrome, scoliosis, and thoracic myelomeningoceles.

OBSTRUCTIVE DISEASES OF THE TRACHEA

37

CONCLUSIONS

Tracheal obstruction is a rare cause of obstructive lung disease. However, when pulmonary function testing suggests a central cause for obstruction, imaging may play an important role in the diagnosis. Many causes of central airway obstruction may be distinguished by this imaging features, especially those featured on CT or MRI imaging.

Fig 12. Sclerosing mediastinitis. This 36-year-old man who had grown up in Michigan presented with chronic pneumonia and wheezing. A chest radiograph (not shown) demonstrated a chronic right lower lobe infiltrate. Unenhanced CT image through the level of the pulmonary arteries demonstrates a poorly marginated calcified mass (white arrows) that surrounds and constricts the bronchus intermedius (small black arrow), This appearance of an infiltrating calcified mass is nearly pathognomonic of scierosing mediastinitis.

This is an exceedingly rare cause of airways obstruction. Lateral chest radiographs may show tracheal compression by the abnormally narrow thoracic inlet. MRI examinations will more accurately depict the level, degree, and mechanism of obstruction and will detect some locations of obstruction not recognized on the chest radiograph. 9j FOREIGN BODIES

Foreign bodies, which are a rare cause of obstructive lung disease in adults, are more common in children. These are most often due to aspirated foodstuffs, especially small round or oval foods such as peas and peanuts. 92 Children may aspirate small toys, and adults may aspirate oral appliances such as denture fragments. 93 Children who aspirate will most often be otherwise of normal health; however, adults will often have predisposing conditions associated with airway compromise, such as neurologic disorders, loss of consciousness, trauma, or drug or alcohol abuse. 93 Foreign body aspiration will most often present as acute respiratory compromise due to airway obstruction. However, in some patients it may be more insidious and present as recurrent episodes of pneumonia. Chest radiographs may demonstrate lobar atelectasis, complete lung collapse, or air trapping, and may reveal the foreign body, when radio-opaque (Fig 13). CT will also demonstrate the secondary abnormalities of airways obstruction and will directly demonstrate the endobronchial foreign material in most c a s e s . 94

Fig 13. Foreign body. This 24-year-old man attempted suicide by aspirating a quarter. (A) PA and (B) lateral radiographs demonstrate a coin lodged in the trachea just above the carina. Most foreign bodies are not radiopaque and require CT to demonstrate their position.

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WALLACE T. MILLER, JR

REFERENCES

1. Gilbert JG, Mazzarella LA, Geit LJ: Primary tracheal tumors in the infant and adult. Arch Otolarnygol Head Neck Surg 58:1-14, 1953 2. Desai DP, Holinger LD, Gonzalez-Crussi F: Tracheal neoplasms in children. Ann Otol Rhinol Laryngol 107:790-796, 1998 3. Sharpe DA, Moghissi K: Tracheal resection and reconstruction: A review of 82 patients. Eur J Cardiothorac Surg 10:1040-1045, 1996 4. deLorimier AA, Hamson MR, Hardy K, et al: Tracheobronchial obstmction in infants and children: Experience with 45 cases. Ann Surg 212:277-289, 1990 5. Kwong JS, Adler BD, Padley SPG, et al: Diagnosis of diseases of the trachea and main bronchi: Chest radiograph vs CT. AJR Am J Roentgenol 161:519-522, 1993 6. Perelman MI, Koroleva NS: Primary tumors of the trachea, in Grillo HC, Eschapasse H (eds): International Trends in General Thoracic Surgery. 1987, pp 91-110 7. Faber LP, Warren WH: Benign and malignant tumors of the trachea, in Shields TW, LoCicero J III, Ponn RB (eds): General Thoracic Surgery (ed 5). Philadelphia, PA, Lippincott Williams & Wilkins, 1999, pp 899-917 8. Houston HE, Payne WS, Harrison EB Jr, et al: Primary cancers of the trachea. Arch Surg 99:132-140, 1969 9. Regnard JF, Fourquier P, Levasseur P: Results and prognostic factors in resections of primary tracheal tumors: A multicenter retrospective study: The French Society of Cardiovascular Surgery. J Thorac Cardiovasc Surg l 11:808-813, 1996 10. Perelman MI, Koroleva N, Birjukov J, et al: Primary tracheal tumors. Semin Thorac Cardiovasc Surg 8:400-402, 1996 11. Kwong JS, Muller NL, Miller RR: Diseases of the trachea and main-stem bronchi: Correlation of CT with pathologic findings. Radiographics 12:645-657, 1992 12. Fraser RS, Genereanz GB: Neoplastic disease of the lungs, in Fraser RG, Pare JAP, Pare PD (eds): Diagnosis of Diseases of the Chest (ed 3). Philadelphia, PA, WB Saunders, 1989, pp 1327-1699 13. Singer DB, Greenberg SD, Harrison GM: Papillomatosis of the lung. Am Rev Respir Dis 94:777-783, 1966 14. A1-Saleem T, Peale AR, Norris CM: Multiple papillomatosis of the lower respiratory tract: Clinical and Pathologic study of eleven cases. Cancer 22:1173-1184, 1968 15. Kramer SS, Wehunt WD, Stocker JT, et al: Pulmonary manifestations of juvenile laryngotracheal papillomatosis. AIR Am J Roentgenol 144:686-694, 1985 16. Grillo HC, Mathisen DJ: Primary tracheal tumors: Treatment and results. Ann Thorac Surg 49:69-77, 1990 17. Mark E: Pathology of tracheal neoplasms, in Choi NC, Grillo HC (eds): Thoracic Oncology. New York, NY, Raven, 1983, pp 256-269 18. Gelder CM, Hetzel MR: Primary tracheal tumors: A national survey. Thorax 48:688-692, 1993 19. Reid JD: Adenoid cystic carcinoma (cylindroma) of the bronchial tree. Cancer 5:685-694, 1952 20. Hadju SI, Huvos AG, Goodner JT, et al: Carcinoma of the trachea. Clinicopathologic study of 41 cases. Cancer 25: 1448-1456, 1970 21. Cleveland RH, Nice CM, Ziskind J: Primary adenoid cystic carcinoma (cylindroma) of the trachea. Radiology 122: 597-600, 1977

22. Spizarny DL, Shepard JA, McCloud TC, et al: Ct of adenoid cystic carcinoma of the trachea. AJR Am J Roentgenol 146:1129-1132, 1986 23. Turnbull AD, Huvos AG, Goodner JT, et al: Mucoepidermoid carcinoma of the bronchial glands. Cancer 28:539-544, 1971 24. Yousem SA, Hochholzer L: Mucoepidermoid tumors of the lung. Cancer 60:1346-1351, 1987 25. Arrigoni MG, Woolner LB, Bernatz PE: Atypical carcinoid tumors of the lung. J Cardiovasc Thorac Surg 64:413-421, 1972 26. de Lima R: Bronchial adenoma: Clinicopathologic study and results of treatment. Chest 77:81-84, 1980 27. Paladugu RR, Benfield JR, Pak HY, et al: Bronchopulmonary Kulchitshy cell carcinomas: A new classification scheme for typical and atypical carcinoids. Cancer 55:13031311, 1985 28. Godwin JD 11: Carcinoid tumors, an analysis of 2837 cases. Cancer 36:5604569, 1975 29. Berge T, Linell F: Carcinoid tumors: Frequency in a defined population during a 12-year period. Acta Pathol Microbiol Scand [A]84:322-330, 1976 30. Briselli M, Mark GJ, Grillo HC: Tracheal carcinoids. Cancer 42:2870-2879, 1978 31. Okike N, Bernatz PE, Woolner LB: Carcinoid tumors of the lung. Ann Thorac Surg 22:270-227, 1976 32. Fraser RG, Pare JAP, Pare PD (eds): Diseases of the Airways, in Diagnosis of Diseases of the Chest (ed 3). Philadelphia, PA, WB Saunders, pp 1969-2275, 1989 33. Dixon TC, Sando JW, Bolton JM, et al: A report of 342 cases of prolonged endotracheal intubation. Med J Aust 2:529533, 1968 34. Pearson FG, Goldberg M, da Silva AJ: Tracheal stenosis complicating tracheaostomin with cuffed tubes: Clinical experience and observations from a prospective study. Arch Surg 97:380-394, 1968 35. Hemmingsson A, Lindgren PG: Roentgenologic examination of tracheal stenosis. Acta Radiol Diagn 19:753-765, 1978 36. Grillo HC: Management of Non neoplastic Diseases of the Trachea, in Shields TW, LoCicero J III, Ponn RB (eds): General Thoracic Surgery (ed 5). Philadelphia, PA, Lippincott Williams & Wilkins, 1999, pp 885-897 37. Goldberg M, Pearson FG: Pathogenesis of tracheal stenosis following tracheostomy with a cuffed tube-an experimental study in dogs. Thorax 27:678-691, 1971 38. Grillo HC: The management of tracheal stenosis following assisted respiration. J Thorac Cardiovasc Surg 57:52-71, 1969 39. James AE Jr, Mac Millian AS Jr, Eaton SB, et al: Roentgenology of tracheal stenosis resulting from cuffed tracheostomy tubes. AJR Am J Roentgenol 109:455-466, 1970 40. Harley HRS: Laryngotracheal obstruction complicating tracheostomy or endotracheal intubation with assisted respiration: A critical review. Thorax 26:493-533, 1971 41. Nottet JB, Duruisseau O, Herve S, et al: Inhalation burns: Apropos of 198 cases: Incidence of laryngotracheal involvement. Ann Otolaryngol Chir Cervicofac 114:220-225, 1997 42. Yang JY, Yang WG, Chang LY, et al: Symptomatic tracheal stenosis in burns. Burns 25:72-80, 1999

OBSTRUCTIVE DISEASES OF THE TRACHEA

43. Gaissert HA, Lofgren RH, Grillo HC: Upper airway compromise after inhalational injury: Complex strictures of larynx and trachea and their management. Ann Surg 218:672678, 1993 44. Braman SS, Gaissert HA: Upper Airway Obstruction, in Fishman AP, Elias JA, Fishman JA, et al (eds): Pulmonary Diseases and Disorders (ed 3). New York, NY, McGraw-Hill, 1998, pp 783-802 45. Hedlund GL, Griscom T, Cleveland RH, et al: Respiratory system, in Kirks DR, Griscom NT (eds): Practical Pediatric Imaging: Diagnostic Radiology of Infants and Children. Philadelphia, PA, Lippincott-Raven, 1998, pp 619-819 46. Strife JL: Pediatric airway obstruction: Imaging in the 1990s, in Kirks DR (ed): Emergency Pediatric Radiology: A Problem Oriented Approach. Reston, VA, American Roentgen Ray Society, 1995, pp 225-232 47. Grillo HC, Mark HC, Mathison DJ, et al: Idiopathic laryngotracheal stenosis: The entity and its management. Ann Thorac Surg 56:80-87, 1993 48. Choplin RH, Wehunt WD, Theros EG: Diffuse lesions of the trachea. Semin Roentgenol 18:38-50, 1983 49. Ell SR, Jolles H, Galvin JR: Cine CT demonstration of non fixed upper airway obstruction. AJR Am J Roentgenol 146:669-677, 1986 50. Dolan DL, Lemmon GB Jr, Teitlebaum SL: Relapsing polychondritis: Analytical literature review and studies on pathogenesis. Am J Med 41:285-299, 1966 51. Pearson CM, Kline HM, Newcomber VD: Relapsing polychondritis. N Engl J Med 263:51-58, 1960 52. Im JG, Chung JW, Han SK, et al: CT manifestations of tracheobronchial involvement in relapsing polychondritis. J Comput Assist Tomogr 12:792-793, 1988 53. Cotch MF, Hoffman BS, Yerg DE, et al: The epidemiology of Wegener's granulomatosis: Estimates of the five-year period prevalence, annual mortality and geographic disease distribution from population-based data sources. Arthritis Rheum 39:87-92, 1996 54. Stin MG, Gamsu G, Webb WR, et al: Computed tomography of diffuse tracheal stenosis in Wegener granulomatosis. J Comput Assist Tomogr 10:868-870, 1986 55. Cordier JF, Valeyre D, Guillevin L, et al: Pulmonary Wegener's granulomatosis: A clinical and imaging study of 77 cases. Chest 97:906-912, 1990 56. Aberle DR, Gamsu B, Lynch D: Thoracic manifestations of Wegener granulomatosis: Diagnosis and course. Radiology 174:703-709, 1990 57. Maskell GF, Lockwood CM, Flower CDR: Computed tomography of the lung in Wegener's granulomatosis. Clin Radiol 48:377-380, 1983 58. Stein MG, Gamsu G, Webb WR, et al: Computed tomography of diffuse tracheal stenosis in Wegener granulomatosis. J Comput Assist Tomogr 10:868-870, 1986 59. Wilcox P, Miller R, Miller G, et al: Airway involvement in ulcerative colitis. Chest 92:18-12, 1987 60. Thompson PJ, Citron KM: Amyloid in the lower respiratory tract. Thorax 38:84-87, 1983 61. Fraser RS, Muller NL, Coleman N, et al (eds): Amyloidosis, in Diagnosis of Diseases of the Chest. Philadelphia, PA, WB Saunders, 1999, pp 2708-2718 62. Gamsu G, Webb WR: Computed tomography of the

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trachea and main stem bronchi. Semin Roentgenol 18:51-59, 1983 63. Bowen DAI: Tracheopathia osteoplastica. J Clin Pathol 12:435-439, 1959 64. Lundgren R, Stjernberg NL: Tracheobronchopathia osteochondroplastica-A clinical, bronchoscopic and spirometric study. Chest 80:706-709, 1981 65. Onitsuka H, Hirose N, Watanabe K, et al: Computed tomography of tracheopathia osteoplastica. AJR Am J Roentgenol 140:268-270, 1983 66, Onitsuka H, Hirose N, Watanabe K, et al: Computed tomography of tracheopathia osteoplastica. AJR Am J Roentgenol 140:268-270, 1983 67. Katz I, LeVine M, Herman P: Tracheobronchomegaly, The Mournier-Kuhn syndrome. AJR Am J Roentgenol 88: 1084-1088, 1962 68. Al-Mallah Z, Quantock OP: Tracheobronchomegaly. Thorax 23:230-234, 1968 69. Bateson EM, Woo-Ming M: Tracheobronchomegaly. Clin Radiol 24:354-358, 1973 70. Johnson RF, Green RA: Tracheobronchiomegaly: Report of five cases and demonstration of familial occurrence. Am Rev Respir Dis 91:35-38, 1965 71. Ettman IK, Keel DT Jr: Tracheal diverticulosis. Radiology 78:187-191, 1962 72. Shin MS, Jackson RM, Ho KJ: Tracheobronchomegaly (Mounier-Kuhn syndrome): CT diagnosis. AJR Am J Roentgenol 150:777-779, 1988 73. Sunne MB, Reiner B: CT features of tracheobronchomegaly. J Comput Assist Tomogr 12:388-391, 1988 74. Rindsberg S, Friedman AC, Fiel SB, et al: MRI of tracheobronchomegaly. J Can Assoc Radiol 38:126-128, 1987 75. Backer CL: Compression of the trachea by vascular rings, in Shields TW, LoCicero J III, Ponn RB (eds): General Thoracic Surgery (ed 5). Philadelphia, PA, Lippincott Williams & Wilkins, 1999, pp 919-934 76. Stark J, Roesler M, Chrispin A, et al: The diagnosis of airway obstruction in children. J Pediatr Surg 20:113-117, 1985 77. Chun K, Colombani PM, Dudgeon DL, et al: Diagnosis and management of congenital vascular rings: A 22-year experience. Ann Thorac Surg 53:597-602, 1992 78. Cosentino CM, Backer CL, Idriss FS, et al: Pericardial patch tracheoplasty for severe tracheal stenosis in children: Intermediate results. J Pediatr Surg 26:879-884, 1991 79. Berdon WE, Baker DH, Wung JT, et al: Complete cartilage-ring tracheal stenosis associated with anomalous left pulmonary artery: The ring-sling complex. Radiology 152:5764, 1984 80. Lowe GM, Donaldson JS, Backer CL: Vascular rings: 10-year review of imaging. Radiographics 11:637-646, 1991 81. McLoughlin MJ, Weisbrod G, Wise DJ, et al: Computed tomography in congenital anomalies of the aortic arch and great vessels. Radiology 1981 : 138:399-403, 1984 82. Bisset GS, Strife JL, Kirks DR, et al: Vascular rings: MR imaging. A JR Am J Roentgenol 149:251-256, 1987 83. Pickhardt PJ, Siegel MJ, Gutierrez FR: Vascular rings in symptomatic children: Frequency of chest radiographic findings. Radiology 203:423-426, 1997 84. Loyd JE, Tillman BF, Atkinson JB, et al: Mediastinal fibrosis complicating histoplasmosis. Medicine 67:295-310, 1988 85. Fraser RG, Pare JAP, Pare PD (eds): Diseases of the

40

mediastinum, in Diagnosis of Diseases of the Chest (ed 3). Philadelphia, PA, WB Saunders, 1989, pp 2794-2920 86. Schowengerdt CG, Suyemoto R, Main FB: Granulomatous and fibrous mediastinitis--A review and analysis of 180 cases. J Thorac Cardiovasc Surg 57:365-379, 1969 87. Karlson KE, Timmes JJ: Granulomata of the mediastinum surgically treated and followed up to nine years. J Thorac Surg 35:617-623, 1958 88. Feigin DS, Eggleston JC, Siegelman SS, et al: The multiple roentgen manifestations of sclerosing mediastinitis. Johns Hopkins Medical Journal 144:1-8, 1979 89. Weinstein JB, Aronberg DJ, Sagel SS: CT of fibrosing mediastinitis: Findings and their utility. AJR Am J Roentgenol 141:247-251, 1983

WALLACE T. MILLER, JR

90. Tong MC, van Hasselt CA: Tuberculous tracheobronchial strictures: Clinicopathological features and managelnent with the bronchoscopic carbon dioxide laser. Eur Arch Otorhinolaryngol 250:110-114, 1993 91. Donelly LF, Bissett GS III: Airway compression in children with abnormal thoracic configuration. Radiology 206: 323-326, 1998 92. Weissberg D, Schwartz I: Foreign bodies in the tracheobronchial tree. Chest 91:730-733, 1987 93. Limper AH, Prakash UP: Tracheobronchila foreign bodies in adults. Ann Intern Med 112:604-609, 1990 94. Berger PE, Kuhn JP, Kuhns LR: Computed tomography of occult tracheobronchial foreign body. Radiology 134:133135, 1980