Topographic variations in the peripheral course of the greater occipital nerve. Autopsy study with clinical correlations.

The description of the peripheral course of the greater occipital nerve (GON) varies in the literature. An autopsy study was done on 20 cases without known headache problems. These findings showed a marked variation in the relation between the GON and nuchal muscles. The trapezius muscle was penetrated by the GON in 45% of cases, the semispinal muscle of the head was penetrated in 90% of cases, and the inferior oblique muscle of head was penetrated in 7.5% of cases. Macroscopic findings of possible compression were made in 11 cases (27.5%), indicating that nerve compression per se may be of minor importance since it seems to exist in the absence of headache.