Open Access Highly Accessed Case Report

The saw-tooth sign as a clinical clue for intrathoracic central airway obstruction

Akira Nakajima1, Takeshi Saraya1, Saori Takata1, Haruyuki Ishii1, Yoko Nakazato2, Hidefumi Takei2, Hajime Takizawa1 and Hajime Goto1*

Author Affiliations

1 Departments of Respiratory Medicine, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka City, Tokyo, 181-8611, Japan

2 Departments of General Surgery, Kyorin University School of Medicine, Tokyo, 181-8611, Japan

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BMC Research Notes 2012, 5:388  doi:10.1186/1756-0500-5-388

Published: 29 July 2012



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.

Case presentation

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.


This report suggests that the so-called saw-tooth sign may be found even in intrathoracic central airway obstruction due to lung cancer.

Saw-tooth sign; Obstructive sleep apnea syndrome; Intrathoracic central airway obstruction; Lung cancer; Three-dimensional thoracic computed tomography; Flow volume curve