Suboccipital Decompression for Occipital Neuralgia

Cervicogenic headaches are a significant cause of head and neck pain, and occipital neuralgia is a common component of these cervicogenic headaches. Occipital injections are commonly performed at the occipital ridge, but this site does not address more proximal entrapments of the nerve in the suboccipital region. Because of the potentially dangerous structures in this region, clinicians have tended to avoid the suboccipital region, despite the pathologies seen in this region. This article discusses the pathology of the region, the alternative techniques, and the novel interventional approach developed for this region, specifically the “Stealth” approach of occipital decompression. DOI : COMING SOON Corresponding author: Andrea Trescot, Pain and Headache Center, 12836 Old Glenn Hwy Eagle River, AK 99654 DrTrescot@gmail.com. 907-622-3715. 907-622-3712 fax. 904-806-6166 cell


Introduction
Injections of the occipital nerve are common office procedures, perceived as safe, but there have been several devastating complications from occipital injections.In 1978, Selander and Sjöstrand 1 predicted spinal cord injuries from intraneural injections, and a group of patients have developed a "locked-in" syndrome, with infarcts of the medulla, or even death, presumably due to intraneural injection of particulate steroids, with retrograde flow to the brain stem and subsequent infarct.Additional catastrophes have occurred after occipital nerve injections in patients with Arnold Chiari or posterior fossa surgeries.These injections resulted in a delayed onset respiratory arrest after apparent unrecognized subdural spread of the medication.All of these complications have been attributed to the use of sharp needles.
For these reasons, a blunt tipped needle and a suboccipital approach to the occipital nerves was developed.The suboccipital nerve decompression, also known as the Stealth decompression, is a technique using high volume injectate within the suboccipital triangle, used to treat occipital neuralgia.This treatment can be considered as part of a treatment algorithm lying between a superficial occipital nerve block and injection of the dorsal root ganglion of C2.

Epidemiology
"Headaches" is a term used to describe a wide variety of clinical entities, including intracranial headaches and "migraines", as well as "tension headaches", and head pain referred from the neck ("cervicogenic headaches").A cervicogenic headache (IHS) criteria for migraines 5 .However, this is usually a bilateral condition, even if only one side is primarily symptomatic, so both are usually treated.

Anatomy
The  Fifty-eight percent of the patients demonstrated greater than 50% pain relief at the six-month follow-up, and at the one-year follow-up, 34.5% still had ongoing relief.
Additionally, the study showed that these patients had an increase in activities, with ADLs improving in 60% of the patients, as well as a significant decrease in opioid use in 56% of the patients.
More recently, Lauretti et al., directly compared

Complications
To date, no complications have been reported, though there is a theoretic risk of local anesthetic toxicity, bleeding, infection, or injection into a vessel (if using a sharp needle).Special care must be taken of patients who have undergone suboccipital surgery, such as a resection for Arnold Chiari malformation; because of the surgery, there is tenting and adhesions of the dura, with a potential spread to the subdural region, and so the procedure should be performed in a safe environment capable of managing hypotension and loss of airway reflexes, and observed for a longer period of time.

Discussion
Options for treatment of occipital neuralgia are limited.Occipital nerve blocks are one option, but they are short lived, on the order of 2 weeks. 10,11In addition, the risks of injections with sharp needles include nerve trauma, intraneural injection, intravascular injection, and bleeding.Selander Another common option for occipital neuralgia is the use of botulinum toxin.However, the effect is also short lived, and needs to be repeated every 12 weeks. 16diofrequency lesioning has been used to destroy the occipital nerve, but the pain recurs, there is a risk of neuroma formation 17 , and there have been reports of death and paraplegia. 18Cryoneuroablation has been used at the C2 DRG as well as the more distal occipital nerve. 11There has also recently been a published description of cryoneuroablation at the inferior oblique under ultrasound. 19However, none of these has been studied for efficacy, and destruction of the nerve may not be the most appropriate technique when the pathology is an entrapment.
Occipital stimulation has also been used effectively to treat intractable headaches, but the systems are expensive (as much as €760,00 or $97,000), with the need for multiple revisions and technical failures. 20 a 1994 presentation, Umberto Rossi described treating occipital neuralgia by dissecting down to the C1-C2 lamina, cutting the IOC to release the GON, which was flattened and pale.After this release, the nerve became round and pink, suggesting that there is a mechanical compression of the GON by the IOC 21 .
largest of the three occipital nerves, the GON, arises from the dorsal root ganglion (DRG) of C2, running inferiorly between the arch of C1 (atlas) and the lamina of C2 (axis), lateral to the lateral atlanto-axial (AA) joint and deep to the inferior oblique capitus (IOC) muscle.The GON then curves medially and cephalad over the IOC [Figure 1].As the GON travels cephalad up the neck, it travels over the posterior surface of the IOC to pierce the semispinalis capitis muscle, deep to the trapezius muscle, [Figure 2], onto the posterior skull through a muscular sling formed by the aponeurosis of the sternocleidomastoid muscle (SCM) and the trapezius muscle at the skull attachment (the conjoined tendon) [Figure 3], where it is joined laterally by the occipital artery.The GON can be found at this point lying in a palpable groove, immediately medial to the occipital artery and lateral to occipital prominence (the inion) [Figure 1].There are several areas of potential entrapment of the GON -Where the GON emerges from the C2 DRG, between the atlas and axis -Between the IOC and the semispinalis capitis muscles -Where the nerve pierces the semispinalis capitis muscle -Where the GON exits from the aponeurosis of the trapezius The GON can connect with the lesser occipital nerve (LON), which arises from the cervical plexus (formed by the upper four ventral cervical rami), as well as the posterior auricular nerve [Figure 3], leading to a variety of clinical presentations.The GON is prone to trauma from flexion/ tension injuries and repetitive neck contractions, which can cause entrapment and/or scarring of the GON, and a head-forward position can entrap the GON at the level of the IOC muscle [Figure 4A and B].The GON can become inflamed and then develop adhesions in the suboccipital region, leading to further entrapment.Plastic surgeons also may "tuck the skin" around the greater and lesser occipital nerves during some cosmetic procedures, causing superficial and deep entrapment of the nerves.Clinical Presentation Occipital neuralgia was first described by Beruto et al. 6 in 1821 as a sharp, electric-like pain radiating from the occiput to the vertex.Occipital nerve pain primarily refers to the occiput, but it may also radiate to the temporal area, forehead, and retro-orbital areas.Since the GON is made up of contributions from C1, C2, and C3 (see Anatomy), there can be a wide range of clinical presentations, including pain and paresthesias of the posterior scalp; the periorbital, temporal, and mandibular regions; and the external ear and mastoid regions, as well the neck and shoulders.Because of connections with the trigeminal cell bodies in the medulla (the cervico-trigeminal complex), the pain of occipital neuralgia can refer to structures innervated by the branches of the trigeminal nerve, such as the forehead, temples, and eyes.

Figure 8 :
Figure 8: Lateral fluoroscopic image showing the needle in the suboccipital space; red shows the level of the spinous processes (red line).Image Courtesy of Gabor Racz, MD

Figure 9 :Figure 10 :
Figure 9: Lateral Fluoroscopic image showing initial contrast location deep to the suboccipital muscles; red line corresponds to the level of the inferior oblique capitus muscle.(Image courtesy of Gabor Racz, MD) 12 showed that intraneural injections of local anesthetics, especially under high pressure, could travel long distances within the nerve, all the way to the spinal cord.He proposed that this centripetal spread could explain the unexpected spinal anesthesia seen with injections near the spine (such as occipital nerve blocks).Blunt-tipped needles have been shown in animals to decrease the risk of injury to the nerves and arteries.Candido et al.13 showed that Whitacre spinal needles did not prevent intravascular injections.Heavner et al.14,15 compared the trauma created by sharp vs.Stealth blunt-tipped needles when attempting to deliberately penetrate kidneys, liver, renal artery, intestine or spinal nerve root, and found that these blunt -tipped needles were less likely than sharp needles to pierce vital structures and/or cause bleeding.

Figure 11 :
Figure 11: Methylene blue suboccipital decompression dissection .One the right is the dye on the occipital nerve form a standard occipital nerve block.On the left is the dye from the stealth decompression bathing the occipital nerve.(Image Courtesy of Gabor Racz, MD)