Intraoperative anatomical variations during greater occipital nerve decompression

SummaryObjectA study was conducted to elucidate anatomical variations of the GON and surrounding occipital tissues.MethodsAnatomical and surgical variations were prospectively recorded for 272 patients who underwent greater occipital nerve (GON) decompression by a single surgeon between 2003 and 2012. Data collection was performed intraoperatively and specifically for the purposes of this study. Documented anatomical variations of the GON and surrounding occipital region included the extension of trapezius musculature to the midline, abnormal lymph nodes, and GON branching. Necessary variations in the surgical procedure were also noted, including resection of a lateral portion of semispinalis capitis muscle and occipital arterectomy.ResultsThe GON pierced the semispinalis muscle in all patients bilaterally. The extension of trapezius musculature to the midline was discovered in 67.3 percent of patients and lymph node enlargement was discovered in 1.5 percent of patients. Branching of the GON was noted in 7.4 percent of patients and muscles or vessels between GON branches were noted in 3.7 percent of patients. Occipital arterectomy was required in 64.0 percent of patients and resection of a lateral segment of semispinalis muscle was required in 10.7 percent of patients.ConclusionsThe new anatomical variations described in this study improve understanding of the intraoperative anatomy of the occipital region and prevent difficulty in finding the GON due to dissection in the wrong plane, ensuring that MH patients receive maximal benefit from surgical treatment.