Occipito-Atlanto (C0-C1) Joints as a Source of Spinal Pain
Pain arising from the joints of the upper spine can occur from arthritic changes or trauma such as a whiplash injury. The joints of the upper spine are also thought to be a potential source of occipital headaches. Dreyfuss first showed the occipito-atlanto pain pattern in healthy volunteers.1 Since then there have been case reports of successful treatment of occipital headaches and neck pain with a fluoroscopically-guided injection of anesthetic and corticosteroids into the occipito-atlanto joints. This treatment however has not been formally enunciated and proven with randomized controlled trials. While no randomized controlled trials exist, there are case reports of successful pain control after successful injection of local anaesthetic or corticosteroid into the occipito-atlanto joint.
In a differential diagnosis, one would also explore non-articular sources of spinal pain. Various websites provide an exhaustive list of extra-articular (e.g., discovertebral, zygopophyseal) sources of spinal pain. An old familiar mnemonic from medical school “VINDICATE” provides a lattice to organize these various causes into vascular, inflammatory, neoplastic, degenerative, infectious, connective tissue disorders, autoimmune disorders, trauma and endocrinopathies. Perhaps a more useful approach is to categorize the same information as Macnab has done in chapter three of Macnab’s Backache, 3rd Edition.2 The broad categories listed include viscerogenic, neurogenic, vascular, spondylogenic, and psychogenic (see Appendix A). This has been further delineated in Kiraldy-Willis’ Managing Low Back Pain, 3rd Edition and Harrisons’ Textbook of Internal Medicine.3,4
This article will focus on the cases where occipito-atlanto (C0-C1) joints have been diagnosed as the source of occipital headaches or neck pain.
Occipito-atlanto injections are demanding, technically intensive, and dangerous procedures. They should not be attempted by anyone of any specialty without extensive prior documented experience in fluoroscopically guided injection techniques. The ability to deal with a rapid onset of life-threatening central nervous system, haemodynamic, and respiratory complications is mandatory. Personnel trained for the task should constantly and directly monitor all patients during the procedure using pulse oximetry, ECG, and respiratory monitoring, as indicated and required. All equipment needed for the treatment of possible complications should be in the room. Knowledge of airway control and the equipment to provide it should be immediately at hand for every procedure.
Occipito-atlanto (C0-C1) joint (craniocervical articulation) injection is performed under fluoroscopic guidance to place a needle into the occipito-atlanto joint for purposes of delivering an aliquot of medication into the joint such as local anaesthetic for diagnostic purposes and/or corticosteroid for putatively therapeutic purposes. The first C0-C1 intra-articular injection was reported in 19895 subsequent to which Dreyfus described three cases in 1994.6 Pain referral patterns have been demonstrated by Dreyfuss7 and Fukui8 after joint capsule distension in normal volunteers generated ipsilateral superior posterior lateral neck pain with occasional temporal and occipital pain. The prevalence, however, is unknown since there has not been any reciprocal evidence of these joints as a pain source in patients with headaches. Except for technique modifications by Dreyfuss and Pauza,9 there has been no further literature since 1994. Two discussions, none of which have been substantiated by prospective randomized controlled data, are that of Pulsed RF neurotomy of C1 by Racz et al and intra-articular prolotherapy.10,11
The occipito-atlanto joint is a true synovial joint that is formed by the articulation of the superior articular facet of the C1 vertebrae and the occiput, positioned anteriolateral to the spinal canal as opposed to true z-joints which are posterior-lateral to the same. More simply stated, it is formed by paired occipital condyles and superior articular facets of the atlas. This joint’s main movement is forward and backward bending. Bogduk has show that it is innervated by the C1 ventral ramus.12,13 The joint has a capsule and straddles the spinal cord and the foramen magnum on either side and is V or bean-shaped, slanting caudally and medially. The vertebral artery is often located overlying the medial one third of the joint and runs medially and diagonally to enter the foramen magnum.14,15 Figures 1 through 5 illustrate the anatomy of the C0-C1 joint including needle target location, arteriograms from several perspectives, and a reformatted CT angiogram with the relative locations of the vertebral artery’s lateral and medial loops.
Although there are no studies correlating specific motion provocation, the innate assumption based on the C0-C1 joint anatomy is that of painful nodding coupled with dominant unilateral occipital pain and possibly the previously-mentioned patterns above after C2/3, C1/2 and, finally, that C3/4 cephalgia has been ruled out despite 4-6 weeks of aggressive conservative care. The premise is to not only provide headache pain relief, but to facilitate rehabilitation of soft tissue restrictions and/or joint segmental motion abnormalities.
Like all injection procedures, occipito-atlanto injections are subject to generic possible complications: infection, bleeding, allergy to injectate, and puncture of adjacent structures. In the context of occipito-atlanto injections, inadvertent injection of the vertebral artery, spinal cord and surrounding dura are significant risks. More specifically, the vertebral artery may be punctured if needle placement is too medial, inferior or lateral. The dural sac or spinal cord may be punctured if needle placement is too medial. Thus puncture of the dural sac and direct spinal cord penetration with the needle are rare complications whose incidence should be minimal if good technique is practiced. The proximity of the vertebral artery to the occipital atlantal joint makes its penetration a potential complication; however, it is an event that can be recognized promptly upon injecting a test-dose of contrast medium prior to administering any other agents. The incidence of inadvertent vertebral artery uptake during this procedure is unknown. Digital subtraction angiography has been shown to enhance detection of inadvertent arterial injection,16 but there is not enough literature on its use in C0-C1 injections and thus there is currently no consensus as to whether or not it should be employed for this procedure. To the author’s knowledge, there has been one reported case of locked-in syndrome while performing a C0-C1 injection.