Modular Classification of Endoscopic Endonasal Transsphenoidal Approaches: Quantitative Anatomical Study

Background: Different endoscopic endonasal transsphenoidal approaches to the sellar region have been described. A few anatomical reports compared some of these variations, mostly with qualitative data.

Objective: To quantitatively compare endoscopic endonasal transsphenoidal approaches to the sellar and parasellar regions, using the concept of “surgical pyramid” with a novel research method.

Material and Methods: Computed tomography data of 10 specimens were registered in a neuronavigation system with a dedicated software (GTxEyesII; ApproachViewer). Four different approaches were performed bilaterally on each specimen: paraseptal, transrostral, extended transrostral (with superior turbinectomy), and transethmoidal (with posterior ethmoidectomy). ApproachViewer allows a real-time quantification and visualization of the surgical pyramid that defines the approach. In the post-dissection phase different areas of interest were contoured at the level of the sellar and parasellar regions. The exposure of these, obtained with each approach, was calculated.

Friedman’s tests with Nemenyi’s procedures post-hoc analysis were used.

3D-HD demonstrative step by step videos of the approaches were recorded on two additional fresh injected specimens.

Results: Each added module led to a statistically significant gain in surgical pyramid volume and exposure of sellar and parasellar regions. The paraseptal approach provides limited exposure of areas of interest and small working volume. At least a transrostral approach is necessary to expose the sella bilaterally. The adequate exposure of the lateral structures requires extended transrostral or transethmoidal approaches.

Conclusion: The present study supports a modular, evidence-based, classification of endoscopic endonasal transsphenoidal approaches.