An Anatomic Study of the External Nasal Nerve

ABSTRACT

After rhinoplasty, numbness of the nasal tip has been reported by many surgeons. The nasal tip receives its main sensory nerve supply from the external nasal nerve. However, investigations of the external nasal nerve have not been previously studied. Therefore, anatomic study of the external nasal nerve was performed. Twenty external nasal nerves were dissected in 10 fresh cadaver noses. On dissection, the exit of the nerve between nasal bone and upper lateral cartilage was identified, and the distance from the point of exit to the midline of the nose was measured. The course and the running plane of the nerve were investigated. The nerve branching was also classified into type I; having only 1 nerve without any branch, type II; having 1 nerve proximally, then splitting into 2 main branches, and type III; having 2 main branches from the point of exit. The point of exit of external nasal nerve from distal nasal bone was located 6.5 to 8.5 mm lateral to nasal midline. Nineteen nerves(95%) run in the same deep fatty layer all the way down to the alar cartilages, but one nerve coursed medially between both medial crura. Regarding the branching type of the nerves, type I was found to be the most common, in 10 of 20 nerves. Type II was observed in 6 and type III was seen in 4. Based on our results, the followings are suggested during a rhinoplasty. First, it is best to avoid deep inter- or intracartiaginous incisions. Instead, the dissection should be maintained directly on the surface of the cartilage. Second, dissection at the junction of nasal bone and upper lateral cartilage area of one side should be limited within 6.5mm from midline. Lastly, when the nasal dorsum is augmented by onlay graft, implants or grafts less than 13 mm wide at rhinion level should be used.