Pros and Cons of C2 Nerve Sectioning/Preservation in Posterior Fusion for Congenital Atlantoaxial Dislocation

Safety and efficacy of the new modified technique for c2 nerve root resection in 3d fluoroscopy navigated instrumentation in the cranio-cervical junction

PURPOSE

Instrumentation of the C1 vertebra requires either mobilization or transection of the C2 nerve root. This study investigates clinical and radiological outcomes and incidences of C2 neuropathic pain after posterior instrumented fusion in the cranio-cervical junction with or without division of the C2 nerve roots.

METHODS

This retrospective study compared two cohorts of patients who underwent instrumented fusion in the cranio-cervical junction. Fifty patients (22 males and 28 females) were operated with complete resection of C2 nerve root ganglion (Ex group), and fifty-one patients (30 men, 21 women) with C2 nerve roots preservation (No group).

RESULTS

The incidence of postoperative C2 neuropathy was eight times lower in the Ex group compared to the No group that was statistical significant, p = 0.039. Surgical time was significantly shorter in the No group (p = 0.001). The fusion rates were very high for both groups, without difference between groups (p = 1.0). Autografting from the iliac crest (p = 0.001) as well as postoperative immobilisation with a hard collar (p < 0.001) were required in fewer patients in the Ex group. Also, patients in the Ex group were mobilised faster after surgery (p = 0.49). Overall, complication rates were similar between groups, but the Ex group demonstrated fewer major medical complications (16% vs 31%). Male sex and iliac bone harvesting demonstrated significantly higher OR for development of postoperative complications (p = 0.023 and p = 0.034 respectively) and postoperative mobilization demonstrated significant higher OR for development of postoperative major complications (p = 0.042).

CONCLUSIONS

Resection of the C2 nerve root ganglion during posterior instrumented fusion of the cranio-cervical junction is safe and rarely leads to C2 neuropathy. The technique tends to mitigate the odds of developing postoperative complications.

Stopping at C2 Versus C3/4 in Elective Posterior Cervical Decompression and Fusion: A 5-Year Follow-up Study

STUDY DESIGN

This is a retrospective cohort study.

OBJECTIVE

In patients undergoing elective posterior cervical laminectomy and fusion (PCLF) with a minimum of 5-year follow-up, we sought to compare reoperation rates between patients with an upper instrumented vertebra (UIV) of C2 versus C3/4.

SUMMARY OF BACKGROUND DATA

The long-term outcomes of choosing between C2 versus C3/4 as the UIV in PCLF remain unclear.

METHODS

A single-institution, retrospective cohort study from a prospective registry was conducted of patients undergoing elective, degenerative PCLF from December 2010 to June 2018. The primary exposure was UIV of C2 versus C3/4. The primary outcome was reoperation. Multivariable logistic regression controlled for age, smoking, diabetes, and fusion to the thoracic spine.

RESULTS

Of the 68 patients who underwent PCLF with 5-year follow-up, 27(39.7%) had a UIV of C2, and 41(60.3%) had a UIV of either C3/4. Groups had similar duration of symptoms (P=0.743), comorbidities (P>0.999), and rates of instrumentation to the thoracic spine (70.4% vs. 53.7%, P=0.210). The C2 group had significantly longer operative time (231.8±65.9 vs. 181.6±44.1 mins, P<0.001) and more fused segments (5.9±1.8 vs. 4.2±0.9, P<0.001). Reoperation rate was lower in the C2 group compared with C3/4 (7.4% vs. 19.5%), though this did not reach statistical significance (P=0.294). Multivariable logistic regression showed increased odds of reoperation for the C3/4 group compared with the C2 group (OR=3.29, 95%CI=0.59-18.11, P=0.170), though statistical significance was not reached. Similarly, the C2 group had a lower rate of instrumentation failure (7.4% vs. 12.2%, P=0.694) and adjacent segment disease/disk herniation (0% vs. 7.3%, P=0.271), though neither trend attained statistical significance.

CONCLUSIONS

Patients with a UIV of C2 had less than half the number of reoperations and less adjacent segment disease, though neither trend was statistically significant. Despite a lack of statistical significance, whether a clinically meaningful difference exists between UIV of C2 versus C3/4 should be validated in larger samples with long-term follow-up.

LEVEL OF EVIDENCE

Level-3.

Technique of C2 Nerve Root Preservation in the Presence of Anomalous Vertebral Artery in Atlantoaxial Operations

While accessing the C1-C2 joint during posterior atlantoaxial fixation, the C2 nerve root along with its perineural venous plexus remains an obstacle for a panoramic visualization of the entry point of the C1 lateral mass and joint preparation. Therefore, many surgeons frequently advocate its intentional sectioning during this approach, with no related major complications.1,2 However, this sectioning has at times been associated with symptoms such as hypoesthesia, numbness, dysesthesia, and neuropathic ulcers.3 Thus C2 nerve root preservation during posterior approach for atlantoaxial dislocation (AAD) could potentially avoid such consequences.4 Its preservation has been described for AAD cases with relatively normal C1-C2 joint anatomy with no osseovascular abnormalities.2 In contrast, attempt at C2 nerve root preservation in patients with congenital AAD harboring bony and vascular anomalies poses a greater challenge owing to a restricted operative space and the potential for perineural venous bleeding during dissection. This is more so for young neurosurgeons in the initial part of their learning curve. Video 1 details the technique of C2 nerve root dissection and preservation in a case of congenital AAD with an anomalous vertebral artery (VA). Computed tomography (CT) of this 30-year-old male patient with spastic quadriparesis showed AAD/basilar invagination with an assimilated C1-arch and right anomalous VA on CT angiography. He underwent C1-C2 joint manipulation and short-segment fixation. At 1-year follow-up, the patient's limb weakness had improved and CT showed good bony fusion. The salient operative steps involve gentle teasing and dissection of perineural soft tissues above and below the nerve root; the key to minimize venous bleeding is to dissect, coagulate, and divide them sequentially. A thorough release of the perineural soft tissues allows adequate nerve root mobilization, which in turn provides clear visualization of the C1-C2 joint space, preventing an undue nerve stretching during the C1-lateral mass screw insertion. The anomalous VA usually lies anterior to the C2 nerve root, and careful imaging evaluation allows its anticipation.3 We do not prefer the easy alternative of C2 nerve root sacrifice because of its inherent complications we noticed in our earlier clinical practice.3.

Combined C1–2 transarticular screw fixation and C1 laminoplasty with interlaminar bone transplant for retro-odontoid pseudotumor: illustrative case

BACKGROUND

The surgical treatment for retro-odontoid pseudotumor (ROP) remains controversial. Posterior C1 laminectomy without fixation occasionally leads to postoperative enlargement of ROP. Because its pathogenesis is associated with atlantoaxial instability, atlantoaxial fixation with C1 laminectomy is commonly performed. Atlantoaxial fixation usually includes transarticular fixation and screw-rod fixation. However, these methods have some issues. That is, in transarticular fixation with C1 laminectomy, the bone grafting area is challenging to obtain. In screw-rod fixation with C1 laminectomy, extensive bleeding occurs at times if the lateral atlantoaxial joint is exposed to the transplant bone grafts.

OBSERVATIONS

Herein, the authors report a case of ROP treated with combined C1–2 transarticular screw fixation and C1 laminoplasty with interlaminar bone transplant, which can help achieve adequate spinal cord decompression and can simultaneously secure the bone grafting area between the laminae. In addition, the volume of intraoperative blood loss decreased. Postoperative magnetic resonance imaging showed sufficient decompression of the spinal cord at the C1 level, and computed tomography performed after 6 months revealed bone union between the C1 and C2 laminae.

LESSONS

Combined C1–2 transarticular screw fixation and C1 laminoplasty with interlaminar bone transplant is a useful method for ROP.

C1-C2 arthroplasty for craniovertebral junction instability: A preliminary proof of concept in human cadavers

Background:

The atlantoaxial complex contributes to significant neck movements, especially the axial rotation. Its instability is currently treated with various C1-C2 fusion techniques. This however, considerably hampers the neck movements and affects the quality of life; a C1-C2 motion preserving arthroplasty could potentially overcome this drawback.

Objectives:

We evaluate the range of motion (ROM) of lateral C1-C2 artificial joints in cadaveric models.

Materials and Methods:

This is an in vitro cadaveric biomechanical study. After C1-C2 arthroplasty through a posterior approach, the C1-C2 ROM was tested in 4 fresh-frozen human cadaveric specimens, before and after destabilization.

Results:

The mean axial rotation demonstrated after the placement of C1-C2 joint implants was 15.46 degrees on the right and 16.03 degrees on the left side; the prosthesis provided stability, with 46% of the baseline C1-C2 axial rotation on either side. The ROM achieved in the other axes was less compared with that of intact specimens. To initiate rotation, a higher moment of 1.5 Nm was required in the presence of joint implants compared to 0.5 NM in unimplanted specimens.

Conclusions:

In our preliminary ROM evaluation, the C1-C2 arthroplasty appears to be stable and provides about half of the range of atlantoaxial rotation. It has the potential for joint motion preservation in the treatment of atlantoaxial instability resulting from lateral C1-C2 joint pathologies.

C2 Nerve Root Preservation During Posterior Fixation for Instability Secondary to Congenital Craniovertebral Junction Anomalies: Feasibility Factors and Related Outcomes

OBJECTIVE

Patients with instability because of congenital craniovertebral anomalies often have complex C1-C2 osseovascular anomalies. C2 nerve root sacrifice has been described to address such difficult anatomy during posterior C1-C2 fixation and has its own downsides. Its preservation as a recent alternative poses greater surgical challenge, and the considerations differ from other causes of craniovertebral junctional instability; the pertaining outcomes have been scarcely studied. The objective of this study was to prospectively determine the feasibility and outcomes related to C2 nerve root preservation in patients with congenital atlantoaxial dislocation (CAAD) after posterior C1-C2 fixation.

METHODS

In this observational study, 63 patients (126 nerve roots) with CAAD after posterior fixation were prospectively assessed. Underlying osseovascular anomalies affecting the feasibility of C2 nerve root preservation, and C2 nerve-related dysfunction at 12 months follow-up were analyzed.

RESULTS

The overall C2 nerve root preservation rate was 89.7%. Even in the presence of extreme joint obliquity/spondyloptosis and anomalous vertebral artery, it was feasible in about three fourths. After preservation, 28.3% patients developed new-onset C2 nerve root dysfunction: neuralgia in 2, dysesthesia in 6, and hypoesthesia/paresthesia in 9. The symptoms were not disabling in most patients.

CONCLUSIONS

In most patients with CAAD, C2 nerve root preservation is feasible despite an aberrant bony and vascular anatomy. A few patients after nerve root preservation develop related symptoms that are conservatively manageable, with no significant adverse consequences. Given the controversy in the literature on C2 nerve sacrifice-related outcomes, we favor an attempt at C2 nerve root preservation.

The enigma of acute worsening after a latent interval in post-operative patients of craniovertebral junction instability

OBJECTIVE

For reasons that are poorly understood and still undocumented, few patients of craniovertebral junction (CVJ) anomalies with instability/atlantoaxial dislocation (AAD) in our practice have been seen to suffer unprecedented acute neurological deterioration with respiratory compromise about 48-72 h post-surgery. This has been specifically observed after an uneventful, stable clinical condition in the immediate postoperative period. This study attempts to elucidate the factors and outcomes related to such latent worsening.

PATIENTS AND METHODS

The 4-year surgical data of 268-patients with CVJ instability (AAD/basilar-invagination) who underwent C1-C2 fixation were retrospectively studied. The relevant factors of 17 patients who showed such deterioration were compared with that of the remaining in a multivariate model.

RESULTS

Seventeen patients had acute neurological worsening with respiratory arrest after a latent period. Ten improved at follow-up. Contrary to the general expectation, poor preoperative neurological score or severe dislocation that needed considerable manipulation did not influence such worsening. Dural injury in patients with associated Chiari malformation and vertebral arterial (VA) injury emerged as independent factors (p < 0.01) associated with this pattern of delayed neurological decline.

CONCLUSIONS

We report our management and outcomes of a unique subset of AAD with neurological worsening in the postoperative period after 48-72 h. Such a subgroup was not previously identified in literature. Dural lacerations in AAD with Chiari, and VA injury seem to predispose to such complications and should be prevented at best. Close observation, and caution regarding early extubation (<72 h) is recommended in this subset despite an apparently uneventful immediate postoperative neurological status.

Postoperative complications of Goel-Harms C1-C2 screw-rod fixation technique for C1-C2 instability after C2 nerve sacrifice, a prospective study over two years follow up

BACKGROUND

Atlantoaxial instability is mainly caused by trauma. C2 nerve is usually needed to be sacrificed for adequate exposure of the lateral mass and screw insertion.

OBJECTIVES

This study aimed to investigate the clinical outcome of postoperative complications of C1 and C2 screw-rod fixation using the Goel-Harms technique for C1-C2 instability after sacrificing the C2 nerve root.

METHODS

Amongst forty patients with C1-C2 pathology, twenty-seven cases were enrolled into the study, then variables, including age, sex, primary pathology, operation duration, postoperative pain, paresthesia, anesthesia, and other specific conditions, were documented. Data analyzed by an expert biostatistician. p-value < 0.05 was considered significant.

RESULTS

Regardless of gender, the most postoperative adverse effect was occipital anesthesia (81.5%). Most of the patients (63%) had both occipital pain and anesthesia one-month post-surgery. At 3- and 6-months post-surgery, occipital pain and anesthesia were seen in 40.7% and 14.8%, respectively.

CONCLUSION

The most common postoperative adverse effect of C2 nerve root scarification after C1-C2 fixation is occipital anesthesia followed by occipital paresthesia and pain, which are reduced in severity over time.

A Prospective, Single-Blinded, Bicentric Study, and Literature Review to Assess the Need of C2-Ganglion Preservation - SAVIOUR's Criteria

Objective

Joint manipulation for craniovertebral junction instability is often hindered by the C2-ganglion (C2G). Our study aims to compare the surgical outcome among patients with or without C2G preservation and discuss the technical nuances.

Methods

We did a prospective, bicentric study and included all the operated patients with craniovertebral junction anomaly. The outcome was assessed by the Pain Numeric Rating Scale, Patient Satisfactions Score, and Stony Brook Scar Evaluation Scale. The fusion was assessed using Lenke fusion grade.

Results

One hundred seventy-one patients (88 in group A and 83 in group B) were included. The most common symptom was spastic quadriparesis (n = 165, 96.5%) with median Nurick grade 3.3. Thirteen patients had suboccipital numbness and 12 patients had paraesthesia. Mean blood loss in group A was 490 ± 96.2 mL and group B was 525 ± 45.7 mL; median operative time was 217.9 and 162.2 minutes in the groups A and B, respectively (p < 0.05). At the follow-up (median, 46.8 months), Lenke fusion grade A was achieved in 92.4% and grade B in 7.6%. A trend suggesting better functional outcomes (numbness, parestheisa, scar outcome, and postoperative ulcer formation) in group A was seen with all 6 patients, who underwent O-C2 fixation, developed pressure sore.

Conclusion

Our results support ganglion preservation, especially in the subset of patients where occipital plating is required. Although the study fails to show any statistical significance, we suggest that one should always start with an ‘intent’ of preservation as the functional outcome is better.

An Unusual Cause of Vertebrobasilar Insufficiency in a Case of Atlantoaxial Dislocation with Anomalous Vertebral Artery

BACKGROUND

Posterior circulation stroke resulting from atlantoaxial dislocation (AAD), although uncommon, is a well-described entity. The normally coursed V3 segment of the vertebral artery (VA) is likely to be stretched because of C1-C2 dislocation and further compromised by the C1-C2 translational mobility. The persistent first intersegmental artery (PFIA), an anomalous variant does not course through the C1 transverse foramen, but rather crosses the posterior C1-C2 joints and is unlikely to be affected by the C1-C2 dislocation. Therefore, a patient with AAD and anomalous VA presenting with stroke should be evaluated for other etiologies of VA compromise.

CASE DESCRIPTION

We report a patient of AAD with PFIA who presented with posterior circulation stroke. Careful radiological evaluation revealed a loose body (LB) adjacent to the medial aspect of the left C1-C2 facet compressing the anomalous VA. Intraoperatively, there was a large LB on the posteromedial border of the joint, compressing the VA. The anomalous VA was mobilized, and the offending element removed followed by fixation of the C1-C2.

CONCLUSIONS

One should be aware of such an etiology of arterial compromise in cases of AAD with coexistent anomalous VA. An underlying LB or large osteophytes resulting from instability may be the offending cause, and needs to be dealt with, as fusion alone may not benefit the patient.

Tailored Posterior-Only Approach for C2 Vertebral Body Lesions: Our Surgical Experience in 10 Patients

BACKGROUND

C2 vertebral body (axis) lesions are often approached anteriorly and combined with posterior stabilization of the craniovertebral junction (CVJ). The anterior approach has its limitations. A posterolateral corridor is an alternative access to the C2 body lesions, and this alone may suffice in selected cases. We describe our experience with C2 body lesions, dealt primarily through a posterior approach, and propose an algorithm in the management of such cases.

METHODS

Ten patients with axis lesions were operated through a midline posterior approach followed by posterior stabilization of the CVJ in the same sitting. Their preoperative and follow-up clinico-radiologic details were reviewed.

RESULTS

The lesions included aneurysmal bone cysts (n = 2), fibrous dysplasia (n = 2), chordoma (n = 2), Ewing sarcoma (n = 1), metastases (n = 1), post-traumatic malunion (n = 1), and post-inflammatory deformity (n = 1). All patients presented with worsening neck pain. Five also had spastic quadriparesis. There were no perioperative complications. All showed clinical improvement at follow-up. Only 2 patients (chordoma: n = 1; aneurysmal bone cyst: n = 1) required an additional anterior procedure.

CONCLUSIONS

Adequate debulking or total excision of lesion, neural decompression, and stabilization of the CVJ for axis body lesions can be achieved through a single midline posterior approach in most cases. If required, an anterior approach may be later added depending on the final histopathology.

How to Transect the C2 Root for C1 Lateral Mass Screw Placement: Case Series and Review of an Underappreciated Variable in Outcome

BACKGROUND

The techniques for atlantoaxial arthrodesis have been modified over the years, and placing C1 lateral mass screws is a modern approach. C2 neuropathy is a complication of concern; however, sacrifice of the C2 nerve is an accepted and often favored adjunct. The impact of the technique for cutting the C2 nerve is not adequately addressed in the literature. The aim of this study was to evaluate the clinical outcomes from a series of roots sacrificed during C1-2 fusion with attention to the C2 transection method.

METHODS

Clinical data were collected from trauma patients who underwent C1 screw fixation for atlantoaxial fusion. Chart review was performed and outcome assessed through telephone surveys to patients who were at least 6 months postoperative. Quality of life, C2 nerve function, neck pain, and head pain were assessed.

RESULTS

Sixty-six roots were divided in 35 patients. There were no cases of occipital neuralgia at routine 3-month follow-up. Delayed telephone surveys were completed in 17 patients and exposed 4 cases of severe head/neck pain but none consistent with occipital neuralgia.

CONCLUSIONS

C2 neuralgia is rare when sharply dividing the C2 root with the aid of bipolar electrocautery at the midportion of the ganglion where it overlies the C1-2 joint. A literature review suggests the impact of the root sacrifice method is an underappreciated modifiable factor in outcome. In future reports, description of the root transection technique is imperative and trials comparing ganglionectomy versus transection proximal to the ganglion or through the ganglion should be considered.

Finding the "Sweet Spot" for C2 Root Transection in C1 Lateral Mass Exposure

BACKGROUND

Atlantoaxial fusion often requires C2 nerve transection for complete C1 lateral mass exposure. Nerve transection is made ideally at the preganglionic segment proximal to the dorsal root ganglion to minimize the risk of postoperative dysesthesias. If the nerve is transected too proximally, cerebrospinal fluid leak may be encountered by violation of the dura and arachnoid where the sensory and motor nerve rootlets exit the subarachnoid space. In this study we aimed to quantify the length of the C2 nerve preganglionic segment using cadaveric specimens and develop a method for reliable intraoperative localization for sectioning during C1-2 arthrodesis.

METHODS

Using microsurgical techniques, 16 C2 nerves from 8 frozen and injected cadaveric cervical spine specimens were dissected. Two key measurements were taken to establish a reliable method of preganglionic segment identification. The "sweet spot" for nerve transection was based on the approximate location of the midpoint of the preganglionic segment.

RESULTS

The final determination of the ideal spot for C2 nerve transection using these calculations was 3 mm lateral to the medial border of the lateral mass.

CONCLUSIONS

This anatomic study found remarkable consistency in the preganglionic segment length. The medial border of the lateral mass appeared to be a consistently reliable landmark for identification of the preganglionic segment of the C2 nerve root. By using relationships between known anatomic structures intraoperatively, safety of atlantoaxial fixation can be optimized to maximize complication avoidance and satisfactory patient outcomes.