Anatomical evaluation of the greater occipital nerve block using embalmed neonatal cadavers

Abstract

BACKGROUND : The greater occipital nerve block is indicated for pain relief in children undergoing, among others, posterior fossa craniotomies. This nerve, which arises from the C2 spinal nerve, travels alongside the occipital artery and provides sensation to the posterior scalp. AIM : The aim of this study was to anatomically determine the location of the greater occipital nerve and accompanying occipital artery, as it travels through the hiatus in the trapezius muscle aponeurosis, in the occipital region, in embalmed neonatal cadavers. SETTING : Study was conducted at the Department of Anatomy, University of Pretoria, South Africa. METHODS : Following ethical approval, the greater occipital nerve and occipital artery were bilaterally dissected and exposed in 35 embalmed neonatal cadavers from the Department of Anatomy at the University of Pretoria. The distance between the external occipital protuberance, the rudimentary mastoid process and the greater occipital nerve was measured, while the relationship between the neurovascular structures was observed. RESULTS : The greater occipital nerves were found to be on average 19.85 mm ± 4.70 mm from the external occipital protuberance in neonates, while the external occipital protuberance and rudimentary mastoid process are 42.55 mm ± 8.46 mm apart. In 77.3% of the specimens, the greater occipital nerve was located medial to the occipital artery, while in the remaining cases, the artery lies between the cutaneous branches of the greater occipital nerve at the trapezius muscle hiatus. CONCLUSION : In this neonatal sample, the greater occipital nerve is located at the approximate mid-point of the line between the external occipital protuberance and rudimentary mastoid process. CONTRIBUTION : Careful aspiration is recommended, because the greater occipital nerve is not always located medial to the occipital artery.