Classification and clinical anatomy of the first spinal nerve: surgical implications

Can Axis C be a navigation route - CT comparison study between actual and virtual C1 transpedicular screw insertion

BACKGROUND

Previous studies mainly reported perpendicular and medial inclination insertion methods for C1 transpedicular screw insertion (TSI). Our recent study showed the ideal C1 transpedicular screw trajectory (TST) can be achieved by medial inclination, perpendicular or even lateral inclination insertion, and Axis C can be a reliable trajectory. The purpose of this study is to confirm Axis C is an ideal C1 TST by comparing the cortical perforation differences between actual C1 TSI and virtual C1 transpedicular screw insertion along Axis C (Virtual C1 Axis C TSI).

METHODS

Firstly, the cortical perforations of the transverse foramen and vertebral canal caused by C1 TSIs in twelve randomly selected patients were evaluated based on their postoperative CT data. Secondly, Virtual C1 Axis C TSIs were performed based on same patients' preoperative CT data. Thirdly, the cortical perforation differences between actual and virtual screws were compared.

RESULTS

In actual C1 TSI group, there were thirteen locations of cortical perforation in the axial plane, with five sides in transverse foramen and eight sides in vertebral canal, the cortical perforation rate was 54.2%; the degree of perforation was mild in twelve locations and medium in one location. In contrast, there was no cortical perforation in Virtual C1 Axis C TSI group.

CONCLUSIONS

Axis C is an ideal trajectory for C1 TSI, it can be utilized as a navigation route for computer assisted surgery system.

Minimally Invasive Preganglionic C2 Root Section for Occipital Neuralgia: 2 Case Reports and Operative Video

BACKGROUND

Occipital neuralgia is a painful condition that is believed to occur from processes that affect the greater, lesser, or third occipital nerves. Diagnosis is often made with a combination of classical symptoms, tenderness over the occipital region, and response to occipital nerve blocks. Cervical computed tomography or MRI may be obtained in multiple positions to detect any impingement. Diagnosis can be made with MRI tractography. Nonsurgical treatments include local anesthetic and steroid injections, anticonvulsant medications, botulinum toxin injections, physical therapy, acupuncture, transcutaneous electrical stimulation, cryoneurolysis, and radiofrequency ablation. Surgical treatments include greater occipital nerve decompression, C2 root section, intradural dorsal root rhizotomy, C1-2 fusion, and occipital nerve stimulation. Although stimulation has been favored in the past decade, complications and maintenance of the devices have led us to return to C2 ganglionectomy.

OBJECTIVE

To report on the use of a minimally invasive technique for C2 ganglionectomy to treat occipital neuralgia.

METHODS

Review demographic, surgery, and outcome data of a minimally invasive C2 root ganglionectomy used to treat to 2 patients with occipital neuralgia.

RESULTS

We report on 2 patients with clinically stereotypical unilateral occipital neuralgia confirmed by greater occipital nerve block, but with no imaging correlate. Both were successfully managed by C2 ganglionectomy through an 18-mm tubular retractor and outpatient surgery. Accompanying text, still photographs, and video describe the technique in detail.

CONCLUSION

Minimally invasive C2 ganglionectomy can be used to successfully treat occipital neuralgia.

Dural arteriovenous fistula of the craniocervical junction along the first cervical nerve: A single-center experience and review of the literature

BACKGROUND

Dural arteriovenous fistulas (DAVFs) of the craniocervical junction (CCJ) are relative rare lesions. Most studies of DAVFs of the CCJ included the fistulas at the foramen magnum, first cervical (C1), and second cervical (C2) level. DAVFs of the CCJ along C1 spinal nerve are rare vascular lesions with distinctive features. Our aim is to review cases of DAVFs of the CCJ along C1 spinal nerve at our institution.

METHODS

From June 2008 and December 2021. We reviewed a consecutive series of intracranial and spinal DAVFs at our institution and collected all patients harboring DAVFs of the CCJ along C1 spinal nerve. Medical charts were retrospectively reviewed regarding patient demographic data (i.e., gender and age), presenting symptoms and signs, treatment methods, and neurological outcome and complications after treatment. All image studies, including cranial computed tomography (CT) scan, cervical magnetic resonance imaging, CT angiography, and digital subtraction angiography (DSA) with rotational CT angiography were analyzed by experienced neuroradiologists. The authors also review of the literature of DAVFs of the C1 spinal nerve.

RESULTS

The authors identified 7 patients, including 5 men (71.4 %) and 2 women (28.6 %) with median age 54 years, range 48-72 years. Subarachnoid hemorrhage (SAH) occurred in 5 (71.4 %) patients, and progressive myelopathy in 2 (28.6 %). All fistulas except one received blood supply from the radiculomeningeal branch of the VA at C1 level. Venous aneurysms, being the source of bleeding, were detected in all fistulas with SAH. All patients except one were treated by surgical management. One fistula was treated by balloon-assisted Onyx embolization. Most patients had good neurological outcome following surgery. Complete obliteration of all fistulas treated by surgery was confirmed by follow-up DSA obtained 1 week after surgery. Two patients developed temporary pain and spasm of the trapezius muscle after the surgery. One patient resulted in poor neurological outcome and died due to sepsis and acute upper gastrointestinal bleeding one month after failed embolization. For patients with SAH, only one patient required ventriculoperitoneal shunt.

CONCLUSIONS

DAVFs of the CCJ along the first spinal nerve are rare and a unique subtype of DAVFs at the CCJ. These fistulas account for 1.74 % of all intracranial and spinal DAVFs in the present study. SAH is the major manifestation of DAVFs at C1 spinal nerve that may be overlooked on routine initial DSA. Rotational CT angiography is useful for clarification of the angioarchitecture of these fistulas, including small feeding artery and venous varix. Surgical treatment by interruption of the intradural draining vein should be the treatment of choice for C1 spinal nerve DAVF.

Modified McKenzie-Dandy operation for a cervical dystonia patient who failed selective peripheral denervation: A case report and literature review

Background:

Cervical dystonia (CD) is a rare and difficult-to-treat disorder. Various neurosurgical options are available, each with its own set of advantages and disadvantages. We investigated using the modified McKenzie-Dandy operation for a patient with CD who failed selective peripheral denervation (SPD).

Case Description:

A 42-year-old man presented left-sided rotational torticollis for 3 years. He was referred for surgery after treating with a variety of oral medications and repeated botulinum toxin injections that became ineffective. For the first operation, the patient underwent SPD (modified Bertrand’s operation); unfortunately, the postoperative outcome was unsatisfactory, and the operation was considered a failure. After his symptoms did not improve after 6 months, the modified McKenzie-Dandy operation was performed. Immediately following surgery, he experienced satisfactory outcomes. He was able to resume his normal activities and employment after 1 month after recovering from his temporary swallowing difficulties. He only complained of minor neck pain and no recurrence was observed after 3 years follow-up.

Conclusion:

For patients who have failed SPD, a modified McKenzie-Dandy procedure is a feasible and effective option. The procedure is relatively safe when performed properly, and the long-term effects can be maintained.

A Rare Anatomical Variation of the Lesser Occipital Nerve

The lesser occipital nerve (LON) is a cutaneous branch of the cervical plexus that arises from the second and sometimes the third spinal nerve and innervates the scalp. During routine dissection of the neck, the LON was observed to arise directly from the spinal accessory nerve. The aberrant nerve measured 1.9 mm in diameter and 10.2 cm in length. Although anatomical variations of the LON such as duplication and triplication have been observed, we believe the origination of this nerve directly and exclusively from the spinal accessory nerve is exceedingly rare. The current case adds to the sparse literature on the variations of the LON and might be of interest to clinicians treating neurological conditions or surgeons operating in the area.

A highly complex variant of the plantaris tendon insertion and its potential clinical relevance

The body is home to a number of unique and intriguing anatomical structures, plenty of which concern the muscles and their tendons. Of these, the plantaris muscle is reported to present a particularly high range of morphological variations. The muscle, passing distally throughout the length of the lower leg, consists of a small muscle belly and a long, thin tendon. It originates, traditionally, on the popliteal surface of the femur and the knee joint capsule, and then inserts to the calcaneal tuberosity. It has been suggested that mid-portion Achilles tendinopathy may be caused by certain plantaris tendon morphologies. This case report describes a new anomalous plantaris tendon insertion, closely related to the Achilles tendon. It comprise four distinct insertions and one direct merge with the calcaneal tendon. The current classification should be extended to accommodate such ‘rare cases’ to facilitate more successful Achilles tendinopathy treatment.

A Review of the History, Anatomy, and Development of the C1 Spinal Nerve

The C1 spinal nerve is a fascinating anatomic structure owing to its wide range of variations. Throughout history, understanding of the cranial and spinal nerves has probably influenced the current conception of this nerve among anatomists. Located at the craniocervical junction, the C1 spinal nerve contributes to the motor innervation of deep cervical muscles through the cervical (anterior) and Cruveilhier's (posterior) plexuses. Sensory functions of this nerve are more enigmatic; despite investigations into its dorsal rootlets, a dorsal root ganglion, and the relationships between this nerve and adjacent cranial and spinal nerves, there is still no consensus regarding its true anatomy. In this article, we review the available literature and discuss some of the developmental models that could potentially explain the wide range of variations and functions of the C1 nerve.

Safety and efficacy of percutaneous pulsed radiofrequency treatment at the C1-C2 level in chronic cluster headache: a retrospective analysis of 21 cases

We performed a study of the safety and efficacy of percutaneous pulsed radiofrequency (PRF) treatment directed at C1 and C2 levels as performed at our local pain clinic in refractory chronic cluster headache (CCH) patients. We identified 21 CCH patients treated with PRF (240 s, max. 45 V, max. 42 °C) directed at the ganglion and/or nerve root of C1 and C2. Data were collected through retrospective analysis of patients' files and include demographic variables, onset and duration of the headache, mean attack frequency, and prior pharmacological treatment. Safety and reduction of attack frequency in the first 3 months after a first PRF treatment was the primary outcome parameter of this study. All patients had been treated with at least two prophylactic drugs and 19 (90%) had previously been treated with verapamil, lithium, and topiramate. Ten patients (47.6%) reported no meaningful effect, four patients (19%) reported a meaningful reduction of < 50%, and seven patients (33.3%) reported a reduction in headache burden of at least 50% in the 3 months following treatment. Two patients reported occurrence or increase in frequency of contralateral cluster attacks. No other adverse events were reported or detected at follow-up. Upper cervical PRF treatment appears to be a safe procedure that could prove effective in the treatment of patients with refractory CCH and warrants a prospective study.

Selective Cervical Denervation for Cervical Dystonia: Modification of the Bertrand Procedure

BACKGROUND

Cervical dystonia, commonly referred to as spasmodic torticollis, is a neurological disorder characterized by aberrant, involuntary contraction of the muscles of the neck and shoulders. One surgical option that can be considered is selective cervical denervation.

OBJECTIVE

To report our modification of the Bertrand procedure for selective cervical denervation.

METHODS

Our modification of the Bertrand procedure for selective cervical denervation is reported with intraoperative photographs and schematic depictions of the operative steps.

RESULTS

We report our modification of the Bertrand procedure for selective cervical denervation, which consists of a combination of C2-6 denervation, myectomy of the splenius capitis and/or semispinalis capitis, myotomy of the levator scapulae when indicated, and myotomy and selection denervation of the sternocleidomastoid. The combination of techniques utilized depends on the subtype and severity of cervical dystonia.

CONCLUSION

Our modification of the original Bertrand procedure for selective cervical denervation represents an alternative surgical strategy for the treatment of cervical dystonia, with the potential advantages and disadvantages discussed.

Benign Enhancing Foramen Magnum Lesions: Clinical Report of a Newly Recognized Entity

Intradural extramedullary foramen magnum enhancing lesions may be due to meningioma, nerve sheath tumor, aneurysm, or meningeal disease. In this clinical report of 14 patients, we describe a novel imaging finding within the foramen magnum that simulates disease. The lesion is hyperintense on 3D-FLAIR and enhances on 3D gradient-echo sequences but is not seen on 2D-TSE T2WI. It occurs at a characteristic location related to the posterior aspect of the intradural vertebral artery just distal to the dural penetration. Stability of this lesion was demonstrated in those patients who underwent follow-up imaging. Recognition of this apparently benign lesion may prevent unnecessary patient anxiety and repeat imaging.

Microsurgical Anatomy of the Hypoglossal and C1 Nerves: Description of a Previously Undescribed Branch to the Atlanto-Occipital Joint

OBJECTIVE

Distal branches of the C1 nerve that travel with the hypoglossal nerve have been well investigated but relationships of C1 and the hypoglossal nerve near the skull base have not been described in detail. Therefore, the aim of this study was to investigate these small branches of the hypoglossal and first cervical nerves by anatomic dissection.

METHODS

Twelve sides from 6 cadaveric specimens were used in this study. To elucidate the relationship among the hypoglossal, vagus, and first and cervical nerve, the mandible was removed and these nerves were dissected under the surgical microscope.

RESULTS

A small branch was found to always arise from the dorsal aspect of the hypoglossal nerve at the level of the transverse process of the atlas and joined small branches from the first and second cervical nerves. The hypoglossal and C1 nerves formed a nerve plexus, which gave rise to branches to the rectus capitis anterior and rectus capitis lateralis muscles and the atlanto-occipital joint.

CONCLUSIONS

Improved knowledge of such articular branches might aid in the diagnosis and treatment of patients with pain derived from the atlanto-occipital joint. We believe this to be the first description of a branch of the hypoglossal nerve being involved in the innervation of this joint.

The computed tomography angiography study of the spatial relationship between C1 transpedicular screw trajectory and V3 segment of vertebral artery

BACKGROUND CONTEXT

To our knowledge, there is no study that has systematically analyzed the relationship between C1 transpedicular screw trajectory and V3 segment of vertebral artery (VA V3 segment).

PURPOSE

To study the relationship between C1 transpedicular screw trajectory and VA V3 segment.

STUDY DESIGN

A morphologic computed tomography angiography (CTA) analysis of the spatial relationship between C1 transpedicular screw trajectory and VA V3 segment.

METHODS

Measurements were made on a workstation by using CTA data of 62 patients. Firstly, parameters related to the relationship between C1 vertebral artery groove (VAG) and vertebral artery (VA) were measured: (A) the shortest distance between the posterosuperior aspect of C1 posterior arch and VA; (B) distance between the outer aspect of VAG and VA; (C) distance between midpoint of VAG and VA; and (D) distance between the inner aspect of the VAG and VA. Then, the central axis of trajectory perpendicular to the coronal plane (axis P) and the central axis of trajectory with a medial inclination (axis M) were designed for the basis of measurements. Parameters related to the relationship between axis P/M and VA V3 segment were measured respectively: (E, E'), distance between insertion point and anterior aspect of VA along axis P/M; (F, F'), the shortest distance between axis P/M and the outer cortex of C1 transverse foramen; and (G, G'), the narrowest width of C1 internal medullary canal along axis P/M.

RESULT

A, B, C, and D were 1.7±1.0 mm, 1.6±0.9 mm, 1.5±0.7 mm, 2.3±1.1 mm, respectively. E, E' were 5.5±1.7 mm and 4.1±2.3 mm. F, F' were 1.9±0.7 mm and 2.9±0.7 mm. G, G' were 3.7±1.4 mm and 4.8±1.2 mm. There was a little interspace between atlas VAG and VA, which was mainly filled with venous plexus.

CONCLUSIONS

There is a close relationship between C1 transpedicular screw trajectory and VA V3 segment. Trajectory with medial inclination technique is suggested especially for female patients.

Morphological characteristics of the cranial root of the accessory nerve

There has been the controversy surrounding the cranial root (CR) of the accessory nerve. This study was performed to clarify the morphological characteristics of the CR in the cranial cavity. Fifty sides of 25 adult cadaver heads were used. The accessory nerve was easily distinguished from the vagus nerve by the dura mater in the jugular foramen in 80% of 50 specimens. The trunk of the accessory nerve from the spinal cord penetrated the dura mater at various distances before entering the jugular foramen. In 20% of the specimens there was no dural boundary. In these cases, the uppermost cranial rootlet of the accessory nerve could be identified by removing the dura mater around the jugular foramen where it joined to the trunk of the accessory nerve at the superior vagal ganglion. The cranial rootlet was formed by union of two to four short filaments emerging from the medulla oblongata (66%) and emerged single, without filament (34%), and usually joined the trunk of the accessory nerve directly before the jugular foramen. The mean number of rootlets of the CR was 4.9 (range 2-9) above the cervicomedullary junction. The CR of the accessory nerve was composed of two to nine rootlets, which were formed by the union of two to four short filaments and joined the spinal root of the accessory nerve. The CR is morphologically distinct from the vagus nerve, confirming its existence.

A comprehensive review with potential significance during skull base and neck operations, Part II: glossopharyngeal, vagus, accessory, and hypoglossal nerves and cervical spinal nerves 1-4

Knowledge of the possible neural interconnections found between the lower cranial and upper cervical nerves may prove useful to surgeons who operate on the skull base and upper neck regions in order to avoid inadvertent traction or transection. We review the literature regarding the anatomy, function, and clinical implications of the complex neural networks formed by interconnections between the lower cranial and upper cervical nerves. A review of germane anatomic and clinical literature was performed. The review is organized into two parts. Part I discusses the anastomoses between the trigeminal, facial, and vestibulocochlear nerves or their branches and other nerve trunks or branches in the vicinity. Part II deals with the anastomoses between the glossopharyngeal, vagus, accessory and hypoglossal nerves and their branches or between these nerves and the first four cervical spinal nerves; the contribution of the autonomic nervous system to these neural plexuses is also briefly reviewed. Part II is presented in this article. Extensive and variable neural anastomoses exist between the lower cranial nerves and between the upper cervical nerves in such a way that these nerves with their extra-axial communications can be collectively considered a plexus.

Microscopic clusters of sensory neurons in C1 spinal nerve roots and in the C1 level of the spinal accessory nerve in adult humans

This study examined C1 spinal nerve roots and their anastomotic connections with the spinal accessory nerve for histological evidence of sensory neurons in adult humans. C1 spinal nerves and roots with the adjacent segments of the spinal accessory nerve and the spinal cord were dissected en bloc from cadaveric specimens, and prepared for histological study. Results show that in 39.3% of specimens studied, no sensory component to the C1 spinal nerve could be identified. The C1 dorsal root was present 35.7% of the time, and when present it always contained neuronal cell bodies. In the remaining specimens, the sensory contribution to the C1 spinal nerve came through an anastomotic connection with the spinal accessory nerve. The investigators were able to identify clusters of neuronal cell bodies along the spinal accessory nerve at the level of C1 in 100% of the specimens examined.

Large dumbbell-shaped c1 schwannoma presenting as a foramen magnum mass

Schwannomas involving the foramen magnum commonly originate from the lower cranial nerves, but they are rarely found arising from the first cervical root. To date, very few cases have been described in the literature. The majority involve either the intradural or extradural compartment but not both. We report the second case of a dumbbell-shaped schwannoma arising from the first cervical root. Our patient presented with hemisensory deficits secondary to brainstem compression at the level of the foramen magnum. The patient underwent a far lateral approach, and a gross total resection was achieved. Preoperative suspicion of the diagnosis is helpful in anticipating displacement and avoiding damage to the surrounding neurovascular structures.

The intracranial denticulate ligament: anatomical study with neurosurgical significance

Object

Knowledge of the detailed anatomy of the craniocervical junction is important to neurosurgeons. To the authors' knowledge, no study has addressed the detailed anatomy of the intracranial (first) denticulate ligament and its intracranial course and relationships.

Methods

In 10 embalmed and 5 unembalmed adult cadavers, the authors performed posterior dissection of the craniocervical junction to expose the intracranial denticulate ligament. Rotation of the spinomedullary junction was documented before and after transection of unilateral ligaments.

Results

The first denticulate ligament was found on all but one left side and attached to the dura of the marginal sinus superior to the vertebral artery as it pierced the dura mater. The ligament always traveled between the vertebral artery and spinal accessory nerve. On 20% of sides, it also attached to the intracranial vertebral artery and, histologically, blended with its adventitia. In general, this ligament tended to be thicker laterally and was often cribriform in nature medially. The hypoglossal nerve was always superior to the ligament, which always concealed the ventral roots of the C-1 spinal nerve. The posterior spinal artery traveled posterior to this ligament on 93% of sides. On one left side, the ascending branch of the posterior spinal artery traveled anterior to the ligament and the descending branch traveled posterior to it. Following unilateral transection of the intracranial denticulate ligament, rotation of the spinomedullary junction was increased by approximately 25%.

Conclusions

Knowledge of the relationships of the first denticulate ligament may prove useful to the neurosurgeon during procedures at the craniocervical junction.