The external nasal nerve is the terminal branch of the anterior ethmoidal nerve. After running down a groove on the inner surface of the nasal bone, it emerges onto the face between the lower edge of the nasal bone and the upper lateral cartilage. It supplies the skin over the lower half of the nose, including the ala, the tip and the vestibule.
| Origin | Anterior ethmoidal nerve, the continuation of the nasociliary branch of the ophthalmic nerve |
|---|---|
| Course | Descends in a groove on the deep surface of the nasal bone and emerges between the nasal bone and the upper lateral nasal cartilage to reach the skin of the nose |
| Motor |
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| Sensory |
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Vesicles on the tip or side of the nose in shingles (Hutchinson sign) indicate involvement of this nasociliary territory and predict a higher risk of eye involvement. The nerve can be injured in rhinoplasty, particularly during dissection over the nasal dorsum and cartilage junction, causing numbness of the nasal tip. It is blocked where it emerges below the nasal bone for procedures on the nasal tip.
Dissection or osteotomy near the junction of the nasal bone and upper lateral cartilage can stretch or cut the nerve, leaving a numb nasal tip that usually improves over months.
A zoster rash on the nasal tip shows involvement of the nasociliary nerve via its external nasal branch, and prompts urgent eye assessment because the same nerve supplies the cornea.
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