Clinical Neurology and Neurosurgery 113 (2011) 289–294 Contents lists available at ScienceDirect Clinical Neurology and Neurosurgery journal homepage: www.elsevier.com/locate/clineuro The importance of the greater occipital nerve in the occipital and the suboccipital region for nerve blockade and surgical approaches – An anatomic study on cadavers Mustafa Güvenc ¸ er a,∗ , Pınar Akyer a , Salih Sayhan b , Süleyman Tetik a a Department of Anatomy, Faculty of Medicine, Dokuz Eylül University, Balc ¸ ova, ˙ Izmir, Turkey b Department of Neurosurgery, Faculty of Medicine, Dokuz Eylül University, Balc ¸ ova, ˙ Izmir, Turkey article info Article history: Received 11 February 2010 Received in revised form 3 November 2010 Accepted 27 November 2010 Available online 3 January 2011 Keywords: Greater occipital nerve Occipital neuralgia Entrapment Nerve blockade abstract Objective: Greater occipital nerve (GON) blockade is an effective method for treatment of occipital neural- gias. Occipital neuralgia or neuropraxis of this region may be seen particularly as a result of compression of the GON. This study shows the relationship between the GON and its external bone landmarks, in order to prevent complications and to perform nerve blockades safely. The study also defines the points where the GON pierces the semispinalis capitis (SSC) and the trapezius, and where the GON passes the obliquus capitis inferior (OCI), and identifies bone landmarks for places where the GON may be entrapped. Materials and methods: In the laboratories of Dokuz Eylül University, Faculty of Medicine Department of Anatomy, 12 GON’s belonging to male adult cadavers fixed in formaldehyde were dissected. Colored silicone was injected to all cadavers and then microdissections were performed under a dissection micro- scope. The lesser occipital nerve, the GON, the greater auricular nerve, and the occipital artery (OA) were dissected. All measurements were made with a 0.1 mm sensitive calipometer. Results: The GON’s diameter at the point where the GON pierces the SSC was found to be 2.5 ± 0.3 mm. The distance between the point where the GON pierces the SSC and the external occipital protuberance (EOP) was 53.6 ± 5.0 mm. The distance between this point and the midline was 9.0 ± 1.9 mm, the distance between this point and the intermastoid line was 11.5 ± 3.9 mm and the distance between this point and the mastoid process was 65.5 ± 5.9 mm. The distance between the midline and the point where the GON pierces the aponeurosis of trapezius (AT) was 47.9 ± 8.0 mm, the distance between this point and the EOP was 15.1 ± 7.0 mm, the distance between this point and the intermastoid line was 17.1 ± 2.8 mm, and the distance between this point and the mastoid process was 59.4 ± 2.3 mm. We measured the distance between the OA and the intermastoid line to be 8.5 ± 6.1 mm vertically and 32.3 ± 3.9 mm horizontally to the midline. Conclusion: In this study, we define the GON’s route in the suboccipital and the occipital region where the nerve pierces the SSC and the AT and where blockade or surgery can be performed. These data will help the surgeon and clinician to avoid complications in this region. © 2010 Elsevier B.V. All rights reserved. 1. Introduction The medial branch of the dorsal ramus of the second cervical nerve is referred to as the greater occipital nerve (GON) [1]. This nerve may also have fibers derived from the dorsal ramus of the C3. It has connections with the third occipital nerve medially and the lesser occipital nerve laterally [2,3]. The GON ascends between the obliquus capitis inferior (OCI) and semispinalis capitis (SSC) ∗ Corresponding author at: Dokuz Eylül University School of Medicine, Depart- ment of Anatomy, Balc ¸ ova, 35340 Izmir, Turkey. Tel.: +90 232 4124363; fax: +90 232 4124363. E-mail address: mustafa.guvencer@deu.edu.tr (M. Güvenc ¸ er). and then pierces the latter muscle. After piercing the aponeurosis of trapezius (AT), it travels with the occipital artery to supply the integument of the scalp as far anterior as the vertex of the skull [3,4]. Compression of the GON in specific neck positions has been proven anatomically. Flexion of the cervical spine stretches the GON where it passes the OCI [5] and extension of the neck causes parestesia and pain because the GON stretches at the point it pierces the AT and the SSC [1,4,6,7]. We may see occipital neural- gia due to nerve damage after posterior cervical or cranial surgical aprroaches [3,4]. Although specific causes, such as whiplash injury, prior skull base surgery, rheumatoid arthritis, nerve entrapment by hypertrophied atlantoaxial ligaments, compression of the GON by an anomalous ectatic vertebral artery, and degenerative C1–C2 arthrosis, are known, most cases are idiopathic [8,9]. 0303-8467/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.clineuro.2010.11.021