Surgical anatomy of greater occipital nerve and its relation to occipital artery

Introduction: The knowledge of the anatomy of greater occipital nerve and its relation to occipital artery is important for the surgeon. Blockage or surgical release of greater occipital nerve is clinically effective in reducing or eliminating chronic migraine symptoms. Aim: The aim of this research was to study the anatomy of greater occipital nerve (GON) and its relation to occipital artery. Also the use of these anatomical measures in local injection of the greater occipital nerve for treatment of migraine. Materials and methods: The study was carried out at the Faculty of Medicine, Alexandria University. The posterior neck and scalp of 25 cadaveric heads were dissected. GON was identified and measured relative to bony landmarks. Delineation of GON and occipital artery relationship was done. Twentypatients sufferingfrommigraine diagnosed according to InternationalHeadacheSociety (IHS) criteria (HIS 2004) were treated usingGONblockade. The landmark forGONinjection was based on the anatomical study. Treatment was assessed using the visual analogue scale for migraine pain. Results: In the anatomical study, theGONwasfoundin all specimens.Thediameter fGONwasmeasured at the lower border of inferior oblique, where it pierced SSC, and after its exit from trapezius muscle. The distance between the point where the GON pierced SSC inferior to the external occipital protuberance (EOP) and lateral to the midline was also measured. The GONwas parallel to the occipital artery. The distance between GON and occipital artery was measured. In the clinical study, 20 patients suffering from migraine were treated with 1.5 ml of 0.5% bupivacaine using GON blockade. The landmark for GON injection was based on the anatomical study. For the right GON: the vertical location inferior to EOP ranged from 19.85 mm to 26.9 mm with a mean of 23.1 mm. The lateral location from EOP ranged from 11.03 mmto 14.65 mmwith a mean of 13.4 mm. For the leftGON: the vertical location inferior toEOPranged from 16.89 mmto 29.5 mmwith a mean of 22.1 mm. The lateral location from EOP ranged from 10.89 mm to 15.31 mm with a mean of 14.1 mm.Pain was improved in 70% of patients within the first hour after the first injection. After 1 month,60% of patients still showed improvement. Conclusion: The knowledge of theanatomyof greater occipital nerveandits relation to occipital artery is important for the surgeon. Blockage or surgical release of greater occipital nerve is clinically effective in eliminating chronic migraine headache.