Introduction

Occipital nerve blocks can be performed for both diagnostic and therapeutic purposes in several pain syndromes. As the occipital nerve is superficial, it may be performed with a high success rate even with blind landmark-based techniques. Although they are safe to apply, it should always be kept in mind that rare but serious complications may occur. A suboccipital compartment block especially requires the utmost attention in terms of serious complications even if performed with the help of fluoroscopy or ultrasound. All these procedures should be performed while taking all reasonable precautions.

Anatomy

The greater occipital nerve consists of the primary dorsal ramus C2 and C3 anatomically. It arises between the 1st and 2nd cervical vertebrae with the lesser occipital nerve and continues from the suboccipital triangle between the nuchal muscles. Then, it passes through the trapezius muscle to innervate the posterior scalp to the vertex [1, 2]. Vital et al. [1] identified two curves separating the path of the nervus occipitalis major in three parts. The dorsal ramus of the C2 nerve root forms the nervus occipitalis major. The first part passes between the root of the nerve and the obliquus capitis inferior muscle under which the nerve makes its first bend in a medial direction. The second part of the nerve extends cranially between the semispinalis capitis muscle on the one side and the obliquus capitis inferior, rectus capitis posterior, and anterior muscle on the other side. The third part of the nerve extends in the lateral direction where the aponeurosis of the trapezius muscle is perforated and the nerve starts its course subcutaneously.

The GON, LON, and OA were seen on the two reference lines by the help of a 3D digitizer. The mean distance between the external occipital protuberance (EOP) and the GON’s most medial branch was 33.5 mm on the superior nuchal line and the mean distance between the EOP and the most medial branch of the OA was 37.4 mm. On the EOP-mastoid process (MP) line, the LON was the lateral third and the GON was on the medial third of the EOP-MP line. On the EOP-MP line, the safe injection points are approximately 3 cm from the EOP, 1 cm inferior parallel to the EOP-MP line, and about 3 cm away from the MP [2] (Figures 18.1 and 18.2).

For ONB, there is an alternate location at the superior nuchalline and research has revealed a relationship between the GON and the OA [5, 6]. At this location, the GON is more superficial and lateral and sits right on top of the superior nuchal line’s bony protuberance, therefore removing worries about pushing the needle into deeper structures (Figure 18.3). In 12 cadaveric specimens, Shimizu et al. [5] assessed the anatomic relationship of the GON to the OA and reported that the GON always crossed over the OA at the level of the superior nuchal line in all specimens (Figure 18.3).

Shim et al. [7] performed ultrasound measurements to record the distance of the GON from the EOP in another study investigating the sonographic anatomy of the GON and OA complex at the superior nuchal line and reported that the GON was located 23.1±3.4 mm from the EOP on the right and 20.5±2.8 mm from the EOP on the left. In addition, the LON is more superficial at the level of the superior nuchal line and joins with the GON above the occiput [8].

Indications

Due to significant phenotypic overlap, it may be clinically difficult to distinguish occipital neuralgia and cervicogenic headache from primary headache disorders such as migraine or tension headache [9, 10].

Incidence: It has been estimated that the general population incidence is 3.2 per 100 000 per year [11]. A wide range of therapies have been identified, but there are no standards [10]. Conservative therapies include physical therapy, icing, avoidance of nerve compression, non-steroidal anti-inflammatory drugs (NSAIDs), manual decompression and blockade of the occipital nerve.

Indications

1. Headache
   
   
   
   • Cluster headache
     
   • Cervicogenic headache
     
   • Migraine headache
     
   • Tension-type headache
     
   • Hemicrania continua
     
   • Chronic daily headache
     
   • Unremitting head and neck pain
     
   • Post-dural puncture headache.
   
   
2. Occipital neuralgia
   
   
   
   • Primary occipital neuralgia
     
   • Secondary occipital neuralgia.
   
   
3. Postherpetic neuralgia

Contraindications

1. Local or systemic infection.
   
2. Coagulopathies.
   
3. Vital function instability.
   
4. Malformation at the injection site (e.g. hemangioma) or previous craniotomy surgery that would change the posterior cranial anatomy [12].
   
5. Allergy to anesthetics and corticosteroids.

In breastfeeding or pregnant women, this procedure should not be done routinely; if necessary, a smaller amount of lidocaine may be used.

Pulsed (PRF) and continuous radiofrequency ablation (RFA) have been described in the current literature for great occipital nerve ablation [10, 13]. Cooled radiofrequency ablation (cRFA) has also been defined [14].

Inclusion Criteria

For patients to be included in an occipital block, four criteria are needed:

Related posts:

Complications of Opiate Therapy Complications of Obturator Nerve Block Complications of Cervical Discography Complications of Intradiscal Therapeutic Procedures Complications of Percutaneous Cordotomy Complications of Stellate Ganglion Block (SGB)