Morphological investigation on olfactory nerve and its clinical significance

Objective:To provide anatomic data for preserving olfaction in anterior craniofacial surgery and delivering drugs through nasal administration into the brain. Methods:30 dry skulls(60 sides)and 30 formalin fixed adult cadaver heads(60 sides)were performed microanatomy dissection, meanwhile, 3 formalin fixed adult cadaver heads injected with constrast medium were scanned with X-ray. Results:The dura mater surrounded olfactory nerves and became continuous with the periosteum on the ethmoid bone. A larvaceous space was identified around the dural sheath of olfactory nerves as they passing through the cribriform foramina. Olfactory nerves, which were divided into nasal concha group and septum group, distributed with the shape of horseshoes. The number of fila olfactoria was(10.33±1.81), the diameter of the root of fila olfactoria (0.90±0.22)mm, and the length of fila olfactoria (10.22±2.20)mm in nasal concha group, as well (6.28±1.04), (1.17±0.24)mm, and (5.91±1.95)mm in septum group. The number of cribriform foramina in each side was about (16.33±2.79) and the diameter of cribriform foramina (1.09±0.52)mm. The dural sheath of olfactory nerves could be visualized in X-ray film. Conclusions:(1) The safe area of operation is 10 mm or less below cribriform plate on nasal septum and 15mm or less below cribriform plate on nasal concha. (2) The larvaceous space around the dural sheath of olfactory nerves may be a reliable pathway to deliver drugs into the brain.