Nerves in the Head and Neck - Optic Nerve

The optic nerve is one of twelve nerves that leave the brain via holes in the skull. These nerves are known as cranial nerves and are numbered. The optic nerve is the 2nd cranial nerve. Like all cranial nerves, the optic nerve is a pair with one on each side of the face. It leaves the skull through a hole behind the eye and connects directly to the back of the eyeball. This hole is called the optic canal (1).

The optic nerve is a sensory nerve - this means it carries information about sensations to the brain. In particular, the optic nerve is responsible for eyesight (vision) and carries information about things you see to the brain. It does not carry any information to muscles and other cranial nerves are responsible for eye movements (1).

The optic nerve passes close to the sinuses in the face and can be affected by cancers growing in that area (commonly referred to by doctors as the skull base or base of skull area). If these cancers press on the nerve and squish it or grow along the nerve, it can cause damage to the nerve that results in changes to vision.

At the severe end, this can result in the complete loss of vision. Usually this process happens slowly, but rarely rapid loss of vision can occur. Nerves heal very poorly and any damage can become permanent after only a short period of time. Damage to the nerve is often painful. As each side of the face has a different optic nerve, damage to one nerve will only affect one eye (2).

Surgery and/or radiotherapy to salivary gland tumours close to the optic nerve can also cause damage to the nerve with similar effects to when the cancer attacks the nerve (Chen et al, 2023; Azzam et al, 2020). The optic nerve is particularly sensitive to radiotherapy and radiotherapy doctors try very hard to avoid it. However, this is not always possible and loss of vision can occur following radiotherapy to the skull base (3).

Adenoid cystic carcinoma is particularly likely to affect the nerves of the face with most adenoid cystic carcinomas attacking nerves (4). The optic nerve can be affected by adenoid cystic carcinoma, particularly if it has originated in the skull base or the tear ducts.

References:

(1) Smith AM, Czyz CN. Neuroanatomy, Cranial Nerve 2 (Optic) [Updated 2022 Nov 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507907/

(2) Rodriguez-Beato FY, De Jesus O. Compressive Optic Neuropathy. [Updated 2023 Aug 23]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK560583/

(3) Ataídes FG, Silva SFBR, Baldin JJCMC. Radiation-Induced Optic Neuropathy: Literature Review. Neuroophthalmology. 2020 Nov 4;45(3):172-180. doi: 10.1080/01658107.2020.1817946. PMID: 34194124; PMCID: PMC8210865.

(4) DeAngelis AF, Tsui A, Wiesenfeld D, Chandu A. Outcomes of patients with adenoid cystic carcinoma of the minor salivary glands. Int J Oral Maxillofac Surg. 2011 Jul;40(7):710-4. doi:10.1016/j.ijom.2011.02.010. Epub 2011 Mar 10. PMID: 21396798.