Tracheobronchomalacia



Tracheobronchomalacia


Melissa L. Rosado-de-Christenson, MD, FACR





Key Facts


Terminology



  • Excessive collapsibility of airway lumen


  • Tracheomalacia = affects trachea


  • Tracheobronchomalacia = affects trachea and bronchi


Imaging Findings



  • Chest radiographs may be normal because they are obtained at end-inspiration


  • CT findings



    • Inspiratory imaging may be normal


    • Coronal tracheal diameter exceeds sagittal diameter


    • Expiratory airway collapse to < 50% of expected luminal area


    • Crescent or lunate tracheal morphology


    • Expiratory collapse of central bronchi in cases of tracheobronchomalacia


    • Exclusion of external compression/mass effect


Top Differential Diagnoses



  • Saber-Sheath Trachea


  • Acquired Tracheal Stenosis


  • Wegener Granulomatosis


  • Relapsing Polychondritis


Pathology



  • Lack of integrity of tracheobronchial cartilages


  • Decreased longitudinal fibers of pars membranacea


Clinical Issues



  • Patients may be asymptomatic; incidental diagnosis


  • Cough, dyspnea, hemoptysis


Diagnostic Checklist



  • CT is imaging study of choice


  • Dynamic airway CT during expiration, forced expiration, or coughing







Axial NECT of a 50 year old man with tracheobronchomalacia shows marked collapse of the lumen of the intrathoracic trachea image. The extrathoracic trachea was normal.






Axial NECT of a patient with tracheobronchomalacia shows marked narrowing of the lumen of the main stem bronchi image. There was also narrowing of the intrathoracic trachea.


TERMINOLOGY


Definitions



  • Malacia = softness



    • Generally used to characterize cartilage or bone


  • Pars membranacea = membranous portion of posterior trachea devoid of cartilage


  • Tracheomalacia = tracheal weakness and propensity for luminal collapse



    • Decrease or atrophy of longitudinal elastic fibers of pars membranacea &/or impairment of cartilage integrity


    • Accentuation of physiologic changes in airway lumen with exaggerated changes in tracheal diameter



      • Normal trachea: Dilates with inspiration and narrows with expiration based on pressure differences


    • Tracheal narrowing most prominent with



      • Forced expiration


      • Cough


      • Valsalva maneuver


  • Tracheobronchomalacia = involvement of trachea and main stem bronchi


  • Bronchomalacia = isolated collapsibility of central bronchi without tracheal involvement


  • Classification



    • Primary or congenital


    • Secondary or acquired


IMAGING FINDINGS


General Features



  • Best diagnostic clue



    • Airway narrowing to < 50% of expected luminal area


    • Typically accentuated by expiration


  • Patient position/location



    • Typically affects intrathoracic trachea


    • Extrathoracic or cervical tracheomalacia is less common


    • May be localized or may affect entire trachea


  • Size: > 50% decrease in airway luminal diameter


  • Morphology: Crescent-shaped with anterior ballooning of pars membranacea into airway lumen



CT Findings



  • Trachea may appear normal on inspiratory CT



    • Airway wall thickness normal


    • May be incidental diagnosis on CT


  • Coronal tracheal diameter may exceed sagittal diameter ⇒ “lunate” tracheal morphology


  • Expiratory reduction of tracheal cross-sectional area



    • Lower threshold criterion for diagnosis than with dynamic expiratory imaging


    • Change between inspiration and expiration > 18% in upper trachea > 28% in mid trachea



      • Leads to probability of tracheomalacia (90-100%)


    • Change in cross-sectional area less than above values → probability that patient does not have tracheomalacia is 95-100%


  • Dynamic CT imaging



    • High sensitivity and good agreement with bronchoscopically visible collapsibility


    • Imaging during coughing; most sensitive method for eliciting tracheal collapse



      • Criterion of > 50% collapse during coughing


      • Affected patients may show greater degrees of collapse ranging from 70-100%


  • Virtual bronchoscopy



    • Paired end inspiratory and dynamic expiratory virtual bronchoscopy


    • May obviate conventional bronchoscopy in patients with contraindications to procedure


  • Evaluation of adjacent structures for exclusion of external compression



    • Mediastinal masses



      • Goiter


      • Bronchogenic and other foregut cysts


    • Children with vascular anomalies



      • Double aortic arch, vascular ring


      • Anomalous left pulmonary artery; pulmonary artery sling


      • Airway obstruction may persist after surgical repair of vascular anomaly in up to 30% of cases


  • Associated abnormalities



    • Air-trapping


    • Children



      • Cardiovascular abnormalities: Patent ductus arteriosus, atrial or ventricular septal defects


      • Bronchopulmonary dysplasia


      • Gastroesophageal reflux


    • Chest wall anomalies, scoliosis, pectus excavatum


MR Findings



  • Evaluation of extrinsic airway abnormalities


  • Advantages



    • No ionizing radiation


    • Multiple assessments with various respiratory maneuvers


Radiographic Findings



  • Radiographs may be completely normal, as they are typically obtained in full inspiration


  • Radiography; low sensitivity of 60%


Imaging Recommendations

Tags: ,
Sep 20, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Tracheobronchomalacia

Full access? Get Clinical Tree
Get Clinical Tree app for offline access