Validation of a grading system for the attachment of the superior turbinate to the sphenoid face

The attachment of the superior turbinate to the sphenoid face may be an important factor in determining the approach for sphenoidotomy. We sought to validate a previously described 4-type grading system for superior turbinate attachment (Type: A, within its medial one-third; B, in its middle one-third; C, to its lateral one-third; and D, directly to the orbit) to the face of the sphenoid sinus and to make recommendations for its use in determining the method of sphenoidotomy (transethmoidal vs transsphenoethmoidal).

Single-slice images through both sphenoid sinus ostia were obtained from axial series of computed tomography (CT) scans. Eighteen (36 ostia) sets of scans were used. Attachment type (A-D) in each image was classified by 10 experienced sinus surgeons and compared against a "gold standard" grading performed by the senior author (A.J.), who was the developer of the grading system.

Mean accuracy was 63% (95% confidence interval [CI], 54%-72%) for the 4-type grading system. When Types A+B and Types C+D were grouped together, mean accuracy was 91% (95% CI, 84%-97%). For the 2-group classification system, bootstrap analysis suggested that 97% of physicians attain an accuracy of at least 80%.

Accuracy using the 4-type classification is too low to be practically useful. Accuracy using the 2-group system may be sufficiently high to be a useful aid in selecting a surgical approach. We recommend a transethmoid sphenoidotomy for Types A and B and a transsphenoethmoidal approach to the sphenoid for Types C and D.