C2 dorsal root ganglion: the central hub for cervicogenic headache.

Orientation and property of fibers of the myodural bridge in humans

To evaluate the efficacy and complications of C2 dorsal root ganglion (DRG) pulsed radiofrequency ablation (RFA) for cervicogenic headache (CEH) and to identify factors related to the outcome of the procedure in this retrospective analysis. Although conventional high-temperature C2 DRG RFA was effective in patients with CEH in previous studies, the effect of pulsed RFA on C2 DRG in cases of CEH has not yet been evaluated. We examined the electronic medical records of consecutive patients who underwent C2 DRG block for CEH from January 2012 to May 2018 at a pain center. Consequent C2 DRG pulsed RFA was performed for patients in whom the headache recurred after an initial period of relief 24hours after the C2 DRG block. A successful outcome was defined as at least 50% pain relief at 6months after C2 DRG pulsed RFA. We also examined variables associated with the outcome and prognostic factors of CEH. Fluoroscopy-guided C2 DRG block was performed in 114 patients with CEH. Forty-five patients received C2 DRG pulsed RFA and 40.0% among them (18/45, success group) had ≥50% pain relief after 6months. There were no post-procedure complications throughout the study period. Significantly more patients in the success group than in the failure group had a definite positive response (≥50% pain relief) to a previous C2 DRG block (P<.001). C2 DRG pulsed RFA may be an effective treatment for patients with CEH, particularly for patients who have previously experienced definite pain reduction after C2 DRG block. However, the limitations of our study design and small number of patients preclude firm conclusions.

Objective To observe the clinical effect on cervicogenic headache (CEH) of pulsed radiofrequency stimulation (PRF) applied to the C2 dorsal root ganglion combined with nerve block.Methods A total of 78 cases diagnosed as CEH were randomly divided into a combined treatment group,a PRF treatment group and a nerve block group.The combined treatment group was given both PRF applied to the C2 dorsal root ganglion and blocking therapy.The other two groups were given only one treatment or the other.All the treatments were once weekly for 3 weeks.Before treatment and 1,3 and 6 months after treatment,all of the patients' headaches were evaluated using a visual analogue scale (VAS).Results At 1,3 and 6 months after treatment,the average VAS scores of all three groups had decreased significantly.The VAS ratings dropped the most in the combined treatment group,followed by the PRF group and then the nerve block group.All the intergroup differences were statistically significant.The combined treatment group's cure rate (88％) was significantly better than that of the PRF group (81％),which was significantly better than that of the nerve block group (54％).Conclusion Combining PRF applied to the C2dorsal root ganglion with nerve block therapy has a synergistic effect on CEH.The curative effect of the combined treatment was better than either PRF or blocking alone. Key words: Headache; C2 dorsal root ganglia; Pulsed electrical stimulation; Radio-frequency electrical stimulation; Nerve blocking

Calcitonin gene-related peptide immunoreactive sensory DRG neurons innervating the cervical facet joints in rats

Myodural bridge (MDB) is a dense connective tissue between suboccipital muscle and dura mater. However, there are few reports on the development and maturation of the human MDB. This study aims to explore the developmental relationship between suboccipital muscle and MDB. 30 head and neck specimens from human fetuses (F) ranging from the 12th to 41st week (W) were made into histological sections. The F12W sections showed evidence that the dura mater dominated by fibroblasts, attached to the posterior atlanto-axial membrane (PAAM) which completely sealed the atlanto-axial space. In the F13W stage, myofibrils of the suboccipital muscle fibers increased significantly in number. At the F14W stage, a gap was observed at the caudal end of the PAAM. Numerous myodural bridge-like structures were observed blending into the dura mater through the gap. At the F19W stage, muscle cells mature. Starting at the F21W stage, the MDB were observed as fibroblasts that cross the atlanto-axial interspace and attach to the dura mater. Therefore, the traction generated by the suboccipital muscles seems to promote the maturity of MDB. This study will provide new morphological knowledge to support future research on the function of the human MDB and regulating the development mechanism of MDB.

Cervicogenic headache is a distinct type of headache described in 1980s by Sjaastad, a Norwegian neurologist. It is a not so uncommon headache, which is usually under-diagnosed resulting in suboptimal quality-of-life. The aim of this study was to review the current recommendations on diagnosis and management of cervicogenic headache. A PubMed search was done for the recent articles on 'cervicogenic headache' published in English literature with the aim of recognizing the current perspectives on cervicogenic headache. The diagnosis of cervicogenic headache is based on clinical criteria mentioned by the International Headache Society (IHS) and Cervicogenic Headache International Study Group (CHISG). Cervical nerve block may confirm the nociceptive source in majority of cases and is included in CHISG criteria. Non-invasive diagnostic methods like echogenicity of muscles, diffusion tensor imaging (DTI) and single-photon emission tomography (SPECT) are proposed by some authors for avoiding complications associated with blocks. Mainstay of management is physical therapy. Surgical interventions for cervical degenerative disease may relief an associated headache but such interventions are not performed solely for cervicogenic headache. Headaches with a cervical spine nociceptive source are increasingly being recognized. Current diagnostic criteria and management options are reviewed here.

This study evaluated the effectiveness and safety of ultrasound-guided pulsed radiofrequency (PRF) at the C2 dorsal root ganglion (DRG), specifically at the C1-2 level, for patients with cervicogenic headaches. The study involved 29 patients with unilateral symptoms from January to July 2023. Headache intensity was measured using the numerical rating scale (NRS), with scores recorded before and after the procedure at specified intervals extending up to 24 weeks. Additionally, the neck disability index (NDI) scores were assessed at baseline, 4, 12 and 24 weeks. The findings demonstrated significantly reduced headache NRS scores at all post-treatment checkpoints, with notable pain relief rates of 13.79% and 72.41% at 4 weeks, and 17.24% and 68.97% at 12 and 24 weeks, respectively. NDI scores also showed significant reductions at all evaluated post-treatment time points. Importantly, no significant adverse events were observed in any of the individuals. Our ultrasound-guided approach could be a safe and effective alternative for managing cervicogenic headaches.

The myodural bridge (MDB) represents specialized fibrous structures establishing connectivity between suboccipital musculature and the spinal dura mater (SDM). The suboccipital muscles, ligaments, and myodural bridge fibers together form a functional unit known as the myodural bridge complex (MDBC). Mechanical stress from suboccipital muscles may contribute to MDB maturation. Integrin α7 (ITGA7) is critical for skeletal muscle attachment to connective tissues, and is involved in the transmission of lateral and longitudinal forces in skeletal muscle. Given the muscle force transmission characteristics of ITGA7 and the dependence of MDB development on force transmission, we hypothesized that ITGA7 serves as a crucial link between RCDmi and the MDB it emits, and may involve in the development of MDBC. To test this, neonatal Sprague-Dawley (SD) rats were randomly allocated to shRNA-ITGA7, shRNA-NC control, lentiviral vectors were injected into the dorsal atlanto-occipital interspace. ITGA7 suppression significantly impaired MDB development and maturation, manifesting as disrupted fiber assembly and RCDmi muscle dystrophy. Ultrastructural analysis revealed disorganized collagen fiber architecture and an abundance of fibroblasts, indicative of immature collagen fibers, further corroborated by Picrosirius red staining. Additionally, ITGA7 knockdown resulted in diminished RCDmi muscle force and altered ECM-related gene expression profiles. A key finding of our study is the importance of ITGA7 as a direct molecular link between suboccipital muscles and MDB, suggesting that mechanical forces from suboccipital musculature fundamentally influence MDB differentiation and maturation. These findings substantiate MDB’s role in force transmission to the SDM and by extension, advance our understanding of the molecular mechanisms underlying MDB development and its physiological significance.

The myodural bridge (MDB) represents specialized fibrous structures establishing connectivity between suboccipital musculature and the spinal dura mater (SDM). The suboccipital muscles, ligaments, and myodural bridge fibers together form a functional unit known as the myodural bridge complex (MDBC). Mechanical stress from suboccipital muscles may contribute to MDB maturation. Integrin α7 (ITGA7) is critical for skeletal muscle attachment to connective tissues, and is involved in the transmission of lateral and longitudinal forces in skeletal muscle. Given the muscle force transmission characteristics of ITGA7 and the dependence of MDB development on force transmission, we hypothesized that ITGA7 serves as a crucial link between RCDmi and the MDB it emits, and may involve in the development of MDBC. To test this, neonatal Sprague-Dawley (SD) rats were randomly allocated to shRNA-ITGA7, shRNA-NC control, lentiviral vectors were injected into the dorsal atlanto-occipital interspace. ITGA7 suppression significantly impaired MDB development and maturation, manifesting as disrupted fiber assembly and RCDmi muscle dystrophy. Ultrastructural analysis revealed disorganized collagen fiber architecture and an abundance of fibroblasts, indicative of immature collagen fibers, further corroborated by Picrosirius red staining. Additionally, ITGA7 knockdown resulted in diminished RCDmi muscle force and altered ECM-related gene expression profiles. A key finding of our study is the importance of ITGA7 as a direct molecular link between suboccipital muscles and MDB, suggesting that mechanical forces from suboccipital musculature fundamentally influence MDB differentiation and maturation. These findings substantiate MDB's role in force transmission to the SDM and by extension, advance our understanding of the molecular mechanisms underlying MDB development and its physiological significance.

Numerous pain generators can be responsible for cervicogenic headache and pain in both the cervical and thoracic regions. A 45-year-old female presented in the clinic with a 20-year history of cervicogenic and migraine headaches, accompanied by a prolonged history of local cervical and interscapular pain. The cervicogenic symptoms were attributed to secondary discrelated changes in the cervical spine, as evidenced by specific provocation behaviors and segmental limitation patterns. The patient was educated regarding the presenting problems, and ergonomic changes were initiated. The limitations were addressed with joint-specific mobilization techniques, accompanied by specific home exercises. The patient demonstrated initial rapid improvements that were characterized by reduced symptoms and increased motion, followed by gradual full motion recovery and resolution of cervicogenic symptoms. This recovery pattern suggests the efficacy of manual techniques in the management of cervicogenic headaches and local cervical syndrome, even in the context of rather prolonged symptoms.

A scanning electron microscopic study performed on three cadaveric specimens focused on the human suboccipital region, specifically, myodural bridge (MDB). This study showed the connection form of the MDB among the suboccipital muscles, the posterior atlanto-occipital membrane (PAOM) and the spinal dura mater (SDM), and provided an ultrastructural morphological basis for the functional studies of the MDB. Since the myodural bridge was first discovered by Hack, researches on its morphology and functions had been progressing continuously. However, at present, research results about MDB were still limited to the gross anatomical and histological level. There was no research report showing the MDB's ultrastructural morphology and its ultrastructural connection forms between PAOM and SDM. A scanning electron microscope (SEM) was used to observe the connection of myodural bridge fibers with PAOM and SDM in atlanto-occipital and atlanto-axial interspaces, and the connection forms were analyzed. Under the SEM, it was observed that there were clear direct connections between the suboccipital muscles and the PAOM and SDM in the atlanto-occipital and atlanto-axial spaces. These connections were myodural bridge. The fibers of the myodural bridge merged into the spinal dura mater and gradually became a superficial layer of the spinal dura mater. MDB fibers merged into the SDM and became part of the SDM in the atlanto-occipital and atlanto-axial space. MDB could transfer tension and pulling force to the SDM effectively, during the contraction or relaxation of the suboccipital muscles. N/A.

BackgroundPrevious studies showed neurography and tractography of the greater occipital nerve (GON). The purpose of this study was determining diffusion tensor imaging (DTI) parameters of bilateral GONs and dorsal root ganglia (DRG) in unilateral cervicogenic headache as well as the grading value of DTI for severe headache. The correlation between DTI parameters and clinical characteristics was evaluated.MethodsThe fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values in bilateral GONs and cervical DRG (C2 and C3) were measured. Grading values for headache severity was calculated using a receiver operating characteristics curve. The correlation was analyzed with Pearson’s coefficient.ResultsThe FA values of the symptomatic side of GON and cervical DRG (C2 and C3) were significantly lower than that of the asymptomatic side (all the P < 0.001), while the ADC values were significantly higher (P = 0.003, P < 0.001, and P = 0.003, respectively). The FA value of 0.205 in C2 DRG was considered the grading parameter for headache severity with sensitivity of 0.743 and specificity of 0.999 (P < 0.001). A negative correlation and a positive correlation between the FA and ADC value of the GON and headache index (HI; r = –0.420, P = 0.037 and r = 0.531, P = 0.006, respectively) was found.ConclusionsDTI parameters in the symptomatic side of the C2 and C3 DRG and GON were significantly changed. The FA value of the C2 DRG can grade headache severity. DTI parameters of the GON significantly correlated with HI.

A connective tissue link between the spinal dura mater and the rectus capitis posterior minor muscle was first described in 1995 and has since been readily demonstrated via dissection, magnetic resonance imaging, and plastinated cross-sections of the upper cervical region (Hack et al. [1995] Spine 20:2484-2486). This structure, the so-called "myodural bridge," has yet to be included in any of the American anatomy textbooks or dissection guides commonly used in medical education. This direct anatomic link between the musculoskeletal system and the dura mater has important ramifications for the treatment of chronic cervicogenic headache. This article summarizes the anatomic and clinical research literature related to this structure and provides a simple approach to dissect the myodural bridge and its attachment to the posterior atlanto-occipital membrane/spinal dura mater complex and summarizes the case for its possible inclusion in medical anatomy curricula.

Cervicogenic headache is a relatively common and still controversial form of headache arising from structures in the neck. The estimated prevalence of the disorder varies considerably, ranging from 0.7% to 13.8%. Cervicogenic headache is a 'side-locked' or unilateral fixed headache characterised by a non-throbbing pain that starts in the neck and spreads to the ipsilateral oculo-fronto-temporal area. In patients with this disorder, attacks or chronic fluctuating periods of neck/head pain may be provoked/worsened by sustained neck movements or stimulation of ipsilateral tender points. The pathophysiology of cervicogenic headache probably depends on the effects of various local pain-producing or eliciting factors, such as intervertebral dysfunction, cytokines and nitric oxide. Frequent coexistence of a history of head traumas suggests these also play an important role. A reliable diagnosis of cervicogenic headache can be made based on the criteria established in 1998 by the Cervicogenic Headache International Study Group. Positive response after an appropriate nerve block is an essential diagnostic feature of the disorder. Differential diagnoses of cervicogenic headache include hemicrania continua, chronic paroxysmal hemicrania, occipital neuralgia, migraine and tension headache. Various therapies have been used in the management of cervicogenic headache. These range from lowly invasive, drug-based therapies to highly invasive, surgical-based therapies. This review evaluates use of drug therapy with paracetamol and NSAIDs, infliximab and botulinum toxin type A; manual modalities and transcutaneous electrical nerve stimulation therapy; local injection of anaesthetic or corticosteroids; and invasive surgical therapies for the treatment of cervicogenic headache. A curative therapy for cervicogenic headache will not be developed until increased knowledge of the aetiology and pathophysiology of the condition becomes available. In the meantime, limited evidence suggests that therapy with repeated injections of botulinum toxin type A may be the most safe and efficacious approach. The surgical approach, which includes decompression and radiofrequency lesions of the involved nerve structures, may also provide physicians with further options for refractory cervicogenic headache patients. Unfortunately, the paucity of experimental models for cervicogenic headache and the relative lack of biomolecular markers for the condition mean much is still unclear about cervicogenic headache and the disorder remains inadequately treated.

During mammalian evolution, the Myodural Bridges (MDB) have been shown to be highly conserved anatomical structures. However, the putative physiological function of these structures remains unclear. The MDB functionally connects the suboccipital musculature to the cervical spinal dura mater, while passing through the posterior atlanto-occipital and atlanto-axial interspaces. MDB transmits the tensile forces generated by the suboccipital muscles to the cervical dura mater. Moreover, head movements have been shown to be an important contributor to human CSF circulation. In the present study, a 16-week administration of a Myostatin-specific inhibitor, ACE-031, was injected into the suboccipital musculature of rats to establish an experimental animal model of hyperplasia of the suboccipital musculature. Using an optic fiber pressure measurement instrument, the present authors observed a significant increase in intracranial pressure (ICP) while utilizing the hyperplasia model. In contrast, surgically severing the MDB connections resulted in a significant decrease in intracranial pressure. Thus, these results indicated that muscular activation of the MDB may affect CSF circulation, suggesting a potential functional role of the MDB, and providing a new research perspective on CSF dynamics.