Deborah Rachelle Shatzkes MD, Presenter: Nothing to Disclose

Bidyut Pramanik MD, Abstract Co-Author: Nothing to Disclose

Seth Kanowitz MD, Abstract Co-Author: Nothing to Disclose

James S Babb PhD, Abstract Co-Author: Nothing to Disclose

Richard Lebowitz, Abstract Co-Author: Nothing to Disclose

Multiplanar CT imaging of the frontal sinus outflow tract (FSOT) is now considered essential in the pre-operative assessment of patients with frontal sinus symptoms. This report addresses the most common entities involved in FSOT compromise, and emphasizes the importance of sagittal imaging in their identification.

25 CT scans of the paranasal sinuses (50 sides) were randomized, blinded, and independently evaluated by two attending neuroradiologists. Sagittal images were reconstructed at 1 mm slice thickness and spacing from a helical axial acquisition of either 0.5 or 0.75 mm slice thickness. The coronal images, all at 3 mm slice thickness and spacing, were acquired directly or were reconstructed from a helical axial data set. The presence of FSOT obstruction by agger nasi cells, the ethmoid bulla, and mucosal disease was assessed, and a degree of confidence was rendered for each of these findings in both the coronal and sagittal planes. The results were compared against a consensus diagnosis, rendered based upon simultaneous reading of the coronal and sagittal images. Generalized estimating equations were used to assess the difference between sagittal and coronal images in terms of reader confidence and agreement of diagnoses with the consensus.

FSOT obstruction occurred secondary to agger nasi impingement in 42/50 sides, ethmoid bulla impingement in 28/50 sides, and mucosal disease in 25/50 sides. Concordance with the consensus diagnosis as well as average reader confidence were significantly higher for diagnoses based on the sagittal images than for those based on coronal images (p = 0.0469 and p = 0.0079, respectively). Significant interobserver variation was observed, highest for the determination of bony impingement, and was felt to reflect the lack of objective criteria for this determination.

The addition of sagittal imaging to routine coronal scans improves both accuracy and reader confidence in the identification of the most common entities involved in FSOT compromise. Significant interobserver variation in defining anatomic obstruction of the FSOT reflects the need for more specific radiographic criteria for this determination.

Shatzkes, D, Pramanik, B, Kanowitz, S, Babb, J, Lebowitz, R, Preoperative CT Interrogation of the Compromised Frontal Sinus Outflow Tract.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4405743.html