The Black Turbinate Sign, A Potential Diagnostic Pitfall: Evaluation of the Normal Enhancement Patterns of the Nasal Turbinates

BACKGROUND AND PURPOSE: Lack of enhancement of a nasal turbinate on MR imaging, known as the black turbinate, has been reported as a finding highly suggestive of invasive fungal rhinosinusitis in immunocompromised patients. Our purpose was to investigate the normal enhancement pattern of nasal turbinates and to determine whether a black turbinate occurs in patients without invasive fungal rhinosinusitis and, if so, to distinguish differentiating features from pathologic enhancement.

MATERIALS AND METHODS: We examined patient medical records and available MR imaging, which included most nasal turbinates in more than 1 sequence. Imaging was performed with contrast, either with or without fat saturation, in patients without invasive fungal rhinosinusitis. All MR images were evaluated for a turbinate enhancement pattern and the presence of nonenhancing areas.

RESULTS: After we applied the exclusion criteria, 75 MR images from each group, with and without fat saturation, were included. Overall, the frequency of observed nonenhancing portions of turbinates, ie, black turbinates, was 30%. Most observed black turbinates were located in the posterior portion of inferior turbinates. Tiny areas of nonenhancement within turbinates were also a common finding.

CONCLUSIONS: A black turbinate is not uncommon on MR images in immunocompetent patients who have no chance of having invasive fungal rhinosinusitis. Benign turbinate nonenhancement improves over subsequent series, has preserved thin peripheral enhancement, and often has thin internal septa. Knowledge of this normal pattern of nasal turbinate enhancement can aid in the differentiation of the benign black turbinate in immunocompetent patients from the pathologic black turbinate seen in patients with invasive fungal rhinosinusitis.