Background: This study maps the course of the lesser occipital nerve and its potential compression sites in the posterior scalp.
Methods: Twenty sides of 10 fresh cadaveric heads were dissected. Two fixed anatomical landmarks were used: the y axis was the vertical midline in the posterior scalp through the midline of the cervical spine. The x axis was a horizontal line drawn between the most anterosuperior points of the external auditory meatus. A topographic map of the lesser occipital nerve and its potential compression points was created.
Results: The lesser occipital nerve emerged from the posterior border of the sternocleidomastoid muscle at an average of 6.4 ± 1.4 cm lateral to the y axis and 7.5 ± 0.9 cm caudal to the x axis. Branches of the occipital artery were found to interact with the lesser occipital nerve in 11 of the 20 hemiheads (55 percent). The mean location of the artery-nerve interaction was 5.1 ± 0.9 cm lateral to the y axis and 2 ± 1.45 cm caudal to the x axis. Two patterns of artery-nerve interaction were seen: a single site of artery crossing over the nerve in nine of 20 hemiheads (45 percent) and a helical intertwining relationship in two of 20 of hemiheads (10 percent). A fascial band was identified to compress the lesser occipital nerve in four of 20 hemiheads (20 percent).
Conclusion: This anatomical study traced the lesser occipital nerve as it courses through the posterior scalp and mapped its potential decompression sites.