Olfaction preservation in anterior cranial base approaches: An anatomic study

OBJECTIVE: To study the anatomic basis for olfaction-sparing anterior crani al base approaches. METHODS: The medial anterior skull base containing the olfactory unit and d elimited by the inner table of the frontal sinus, the lesser wing of tile s phenoid bone, and the medial orbital walls was removed from six cadaveric s pecimens. Histological methods were used to investigate the location, distr ibution, and depth of penetration of olfactory nerves. Hematoxylin and eosi n and Gomori trichrome staining were used to visualize landmarks and archit ecture, S-100 neurofilament protein immunostaining was used to identify ner ve fascicles and axons. In three cadaveric head specimens, olfaction-sparin g craniofacial approaches were performed and the excised olfactory units we re evaluated histologically. RESULTS: Bundles of olfactory nerves were identified primarily in the nasal septum; relatively fewer bundles could be identified in the middle turbina te, Olfactory nerve endings were identified up to 20 mm below the cribrifor m plate (range, 7-20 mm). The superior and middle nasal meatus were most in nervated; olfactory innervation was virtually absent in the inferior nasal meatus. Histological evaluation of the olfactory unit elevated during olfac tion-sparing techniques routinely revealed transection of olfactory nerves that exited the skull base. CONCLUSION: In olfaction-sparing anterior cranial base approaches, the olfa ctory nerves are inevitably transected. The clinical significance of olfact ory nerve transection for postoperative functional recovery of olfaction re mains to be analyzed.