Occipital nerves are a group of nerves that arise from C2 and C3 of spinal nerves. They innervate the posterior scalp up as far as the vertex and other structures as well, such as the ear. There are three major occipital nerves in the human body: the greater occipital nerve, the lesser occipital nerve, and the third occipital nerve. Occipital blocks are frequently used to treat migraine headaches and occipital neuralgia. The greater occipital nerve is formed from the posterior division (dorsal ramus) of the C2 nerve. The lesser occipital nerve is formed from the dorsal ramus of C3. The first three cervical sensory nerve roots (C1-C3) anastomose with the descending tract of the trigeminal nerve in the upper cervical cord. This accounts for the referral of pain to the areas such as the orbit, which is innervated by the trigeminal nerve.
The nerve block can be used in primary (migraine, cluster headache, and nummular headache) and secondary headaches (cervicogenic headache and headache attributed to craniotomy), as well in cranial neuralgias (trigeminal neuropathies, glossopharyngeal and occipital neuralgias). (Dach et al, 2015)
The proximity of sensory neurons in the upper cervical spinal cord to the trigeminal nucleus caudalis (TNC) neurons and the convergence of sensory input to TNC neurons from both cervical and trigeminal fibers underscore the rationale of using greater occipital nerve block (GON-block) for acute and preventive treatment in various headache disorders. (Chowdhury et al, 2021)
The inhibition of the occipital nerve block on trigeminal nociceptive activity is likely to occur at the C2 level where the occipital nerve enters the trigeminocervical complex and converges on the same central nuclei before the signal crosses the midline at that level and is then transmitted to higher processing centres. (Hoffman et al, 2021)
Peripheral nerve block techniques include blockage of the greater and lesser occipital nerves, as well as some branches of the trigeminal nerve, such as the supraorbital, supratrochlear, and auriculotemporal nerves (3). Greater occipital nerve (GON) block is a commonly used peripheral nerve block method in migraine treatment. The effect of GON block is observable in the trigeminovascular system, which plays a vital role in the pathophysiology of migraine. (Inan et al, 2019)
Anesthetic nerve blocks may have a dual role in both supporting diagnosis and providing pain relief. While this intervention is sensitive, it is not specific. Many other primary headache disorders including migraine, tension-type headache, and cluster headache may also demonstrate a similar response. (Barmherzig et al, 2019)
The patient is usually positioned in the sitting position with the head either vertical or slightly flexed. The nerve is relatively easy to locate along the superior nuchal line, where it lies medial to the occipital artery, bilaterally. The pulsation of the occipital artery is easy to palpate. Palpation in this area may elicit a paresthesia or uncomfortable feeling in the distribution of the nerve. It is helpful if an assistant provides support for the head anteriorly. The scalp is prepped with alcohol. A mixture of local anesthetic and steroid is used, usually 2% lidocaine with either triamcinolone 10 to 20 mg or betamethasone 2 to 4 mg for a total volume of 3 mL of injectate. The technique is made easier if a control-type syringe is used for aspiration and injection, as this can be performed with one hand. Usually a 25 G needle can be used depending on the size of the patient. The needle is directed at 90 degrees toward the occiput until a bony endpoint is obtained. Aspiration is important to prevent intravascular injection, and in the case of a history of a cranial defect, to prevent injection into the cerebrospinal fluid. Approximately 1.0 cc is injected around the nerve and an additional 1.0 cc on either side of the nerve. When the needle is withdrawn, pressure should be maintained over the site of injection to both bathe the nerve trunk with the mixture and to achieve hemostasis as the scalp has a rich vascular supply. Ample time should be allowed for the local anesthetic to take effect, and the patient should be reevaluated in approximately 15 minutes. The lesser occipital nerves may be included by injecting more of the local anesthetic/steroid mixture lateral to the greater occipital injection along the superior nuchal line. If a small volume is used (approximately 1.0 cc) and is directed in the immediate vicinity of the greater occipital nerve, it is somewhat more definitive in distinguishing greater occipital neuralgia from surrounding myofascial-type pain, which will also be relieved by the injection of a larger volume. (Ward, 2003)
Locate the transverse process of the C2 vertebrae with ultrasound and a the use a high-frequency linear probe to find the greater occipital nerve between the muscle planes of the obliquus capitis inferior and semispinalis capitis. A possible solution to be used is 1 mL of methylprednisolone (40 mg/mL) and 2 mL of 0.5% bupivacaine. (Skinner & Kumar, 2021)
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Hoffmann J, Mehnert J, Koo EM, May A. Greater occipital nerve block modulates nociceptive signals within the trigeminocervical complex. J Neurol Neurosurg Psychiatry. 2021 Dec;92(12):1335-1340. doi: 10.1136/jnnp-2021-326433. Epub 2021 Jul 26. PMID: 34312221.
Inan LE, Inan N, Unal-Artık HA, Atac C, Babaoglu G. Greater occipital nerve block in migraine prophylaxis: Narrative review. Cephalalgia. 2019 Jun;39(7):908-920. doi: 10.1177/0333102418821669. Epub 2019 Jan 6. PMID: 30612462.
Barmherzig R, Kingston W. Occipital Neuralgia and Cervicogenic Headache: Diagnosis and Management. Curr Neurol Neurosci Rep. 2019 Mar 19;19(5):20. doi: 10.1007/s11910-019-0937-8. PMID: 30888540.
Ward JB. Greater occipital nerve block. Semin Neurol. 2003 Mar;23(1):59-62. doi: 10.1055/s-2003-40752. PMID: 12870106.
Skinner C, Kumar S. Ultrasound-Guided Occipital Nerve Block for Treatment of Atypical Occipital Neuralgia. Cureus. 2021 Oct 7;13(10):e18584. doi: 10.7759/cureus.18584. PMID: 34765351; PMCID: PMC8575339.