Anatomic relationship of the first olfactory neuron and trochlea: cadaveric study with surgical implications

Background

Iatrogenic injury to the trochlea is a potential complication of the Draf III or endoscopic modified Lothrop procedure; however, the location of the trochlea from within the sinus cavity has yet to be clearly characterized. We performed the first cadaveric study assessing the position of the trochlea in relation to the first olfactory neuron, a commonly identified landmark during the Draf III procedure.

Methods

Thirteen external dissections of the trochlea were performed on 7 disarticulated cadaveric heads via an extended Lynch type incision. An endoscopic Draf III procedure was then performed on all cadavers. A burr hole was then created at the trochlear fovea. A straight vector between the trochlear attachment and the ipsilateral first olfactory neuron was then created. The vector was then viewed from within the sinuses using a 30-degree endoscope. The endoscope was maneuvered to create an upright midline view centered on the olfactory neurons. An image was subsequently captured and analyzed using ImageJ software to calculate a vector angle. The linear distance between the 2 structures was also recorded.

Results

Relative to the first olfactory neuron, the trochlea was found to be 19.52 ± 4.68 mm away and at an angle of 39.42 ± 8.54 degrees in the anterolateral, superior direction along the frontal bone.

Conclusion

We report the first anatomical dissection characterizing the position of the trochlea relative to the ipsilateral first olfactory neuron. Intraoperative recognition of this relationship during Draf III procedures can prevent potential injury to the trochlea.

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