A Novel Radiologic Sign for Diagnosis of Complete Laryngotracheal Separation
Complete Laryngotracheal Separation
Case 1 A 66-year-old male sustained trauma to the neck after a suicide attempt by hanging. The patient was intubated prior to arrival to our institution and the Otolaryngology service was consulted after imaging studies were performed. Physical exam revealed extensive subcutaneous emphysema and loss of anterior neck landmarks. Laryngotracheal separation (LTS) was diagnosed based on clinical and imaging findings. Case 2 A 7-year-old male was involved in a motor vehicle accident. Upon arrival, the patient was in respiratory distress and intubation was necessary. Physical exam revealed subcutaneous emphysema but palpable neck landmarks. A CT scan of the neck showed subcutaneous emphysema, but no laryngeal injuries were reported at that time. Four days after the trauma, the patient was extubated and developed progressive dysphonia and stridor. Flexible laryngoscopy showed bilateral vocal cord paralysis and subglottic narrowing. In the operating room, bronchoscopy showed subglottic narrowing and neck exploration revealed complete LTS. Case 3 A 35-year-old male sustained multiple body trauma after a motor vehicle accident. No obvious anterior neck trauma was noted at the time and cervical CT scan report was only remarkable for a C7 fracture. Hospitalization was complicated, and a tracheostomy was done due to prolonged mechanical ventilation. The patient was consulted to the otolaryngology service one month after the trauma because he did not tolerate tracheostomy capping trials in preparation for decannulation. On flexible laryngoscopy, the subglottic region was obstructed by soft tissue. A neck CT scan was ordered and LTS was diagnosed.
Three cases of laryngotracheal separation (LTS) are presented along with a novel CT scan finding that facilitates radiologic diagnosis. Our finding, the “telescope sign”, is best described as the superior displacement of the laryngeal skeleton, resulting in telescoping of the thyroid cartilage behind the hyoid bone, obliterating the thyrohyoid (hyolaryngeal) distance. This abnormal imaging relationship has never been described in the past in the setting of laryngeal trauma.
Although examination and radiologic findings can suggest a LTS diagnosis, clinical presentation is characteristically variable and delays in diagnosis and management are widely reported. Furthermore, presenting symptoms may not always correlate with the extent of injury. CT scan plays a central role in establishing a diagnosis and characterizing the injury, however, reported findings are inconstant. Some of them include separation of the cricoid and tracheal cartilages, non-alignment of the laryngotracheal airway, abrupt change in airway caliber, a ragged airway, or an endotracheal tube tip outside the airway lumen. Our finding, the "telescope sign", appears to be present in all three reported cases of LTS despite variable clinical presentation and heterogeneous imaging findings. We have additionally identified several past reports of LTS that demonstrate the “telescope sign” in the included figures. Although several known radiologic features of LTS are described in these studies, this anomalous hyolaryngeal relationship (the “telescope sign”) has been overlooked by the authors. The "telescope sign" is also anatomically sound in the setting of severe airway trauma, as separation of the cricoid cartilage from the trachea causes lack of inferior traction on the laryngeal cartilages and secondary superior excursion and abnormal positioning of the laryngeal framework. We believe our radiologic finding can aid clinicians and radiologists alike in suspecting a diagnosis of LTS, especially in those cases with a more insidious clinical presentation. Furthermore, the “telescope sign” is anatomically simple to understand and easily identified, even when other signs of severe airway injury are absent.
The “telescope sign” refers to superior telescoping of the thyroid cartilage behind the hyoid bone. It is easily identified on CT scan and its presence in trauma patients suggests a diagnosis of complete laryngotracheal separation.