title: The saw-tooth sign as a clinical clue for intrathoracic central airway obstruction.
abstract: BACKGROUND
  The saw-tooth sign was first described by Sanders et al in patients with obstructive sleep apnea syndrome as one cause of extrathoracic central airway obstruction. The mechanism of the saw-tooth sign has not been conclusively clarified. The sign has also been described in various extrathoracic central airway diseases, such as in burn victims with thermal injury to the upper airways, Parkinson's disease, tracheobronchomalacia, laryngeal dyskinesia, and pedunculated tumors of the upper airway.
  
  
  METHODS
  A 61-year-old man was referred to our hospital with a two-month history of persistent dry cough and dyspnea. He was diagnosed with lung cancer located in an intrathoracic central airway, which was accompanied by the saw-tooth sign on flow-volume loops. This peculiar sign repeatedly improved and deteriorated, in accordance with the waxing and waning of central airway stenosis by anti-cancer treatments.
  
  
  CONCLUSIONS
  This report suggests that the so-called saw-tooth sign may be found even in intrathoracic central airway obstruction due to lung cancer.
authors: Departments of Respiratory Medicine, Kyorin University School of Medicine, Tokyo, Japan.
authors: Akira
authors: A
authors: Nakajima
authors: Takeshi
authors: T
authors: Saraya
authors: Saori
authors: S
authors: Takata
authors: Haruyuki
authors: H
authors: Ishii
authors: Yoko
authors: Y
authors: Nakazato
authors: Hidefumi
authors: H
authors: Takei
authors: Hajime
authors: H
authors: Takizawa
authors: Hajime
authors: H
authors: Goto
mesh_terms: D000402:Airway Obstruction / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology / Q000628:therapy; D001706:Biopsy; D001999:Bronchoscopy; D002294:Carcinoma, Squamous Cell / Q000150:complications / Q000175:diagnosis* / Q000628:therapy; D003371:Cough / Q000209:etiology; D004417:Dyspnea / Q000209:etiology; D006801:Humans; D021621:Imaging, Three-Dimensional; D008168:Lung / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D008175:Lung Neoplasms / Q000150:complications / Q000175:diagnosis* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted; D012129:Respiratory Function Tests; D014057:Tomography, X-Ray Computed; D014135:Tracheal Stenosis / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology / Q000628:therapy