An anatomic and morphometric study of C2 nerve root ganglion and its corresponding foramen

A Morphometric Study of the Pars Plana of the Ciliary Body in Human Cadaver Eyes

This study aimed to determine the pars plana length in postmortem human eyes using advanced morphometric techniques and correlate demographics to ocular metrics such as age, sex, ethnicity, and axial length. Between February and July 2005, we conducted a cross-sectional observational study on 46 human cadaver eyes deemed unsuitable for transplant by the SBO Eye Bank. The morphometric analysis was performed on projected images using a surgical microscope and a video-microscopy system with a 20.5:1 correction factor. The pars plana length was measured three times per quadrant, with the final value being the mean of these measurements. Of the 46 eyes collected, 9 were unsuitable for the study due to technical constraints in conducting intraocular measurements. Overall, the average axial length was 25.20 mm. The average pars plana length was 3.8 mm in all quadrants, with no measurements below 2.8 mm or above 4.9 mm. There were no statistically significant variations across quadrants or with age, sex, axial length, or laterality. Accurately defining the pars plana dimensions is crucial for safely accessing the posterior segment of the eye and minimizing complications during intraocular procedures, such as intravitreal injections and vitreoretinal surgeries.

Abnormal spinal cord motion at the craniocervical junction in hypermobile Ehlers-Danlos patients

OBJECTIVE

The craniocervical junction (CCJ) is anatomically complex and comprises multiple joints that allow for wide head and neck movements. The thecal sac must adjust to such movements. Accordingly, the thecal sac is not rigidly attached to the bony spinal canal but instead tethered by fibrous suspension ligaments, including myodural bridges (MDBs). The authors hypothesized that pathological spinal cord motion is due to the laxity of such suspension bands in patients with connective tissue disorders, e.g., hypermobile Ehlers-Danlos syndrome (EDS).

METHODS

The ultrastructure of MDBs that were intraoperatively harvested from patients with Chiari malformation was investigated with transmission electron microscopy, and 8 patients with EDS were compared with 8 patients without EDS. MRI was used to exclude patients with EDS and craniocervical instability (CCI). Real-time ultrasound was used to compare the spinal cord at C1-2 of 20 patients with EDS with those of 18 healthy control participants.

RESULTS

The ultrastructural damage of the collagen fibrils of the MDBs was distinct in patients with EDS, indicating a pathological mechanical laxity. In patients with EDS, ultrasound revealed increased cardiac pulsatory motion and irregular displacement of the spinal cord during head movements.

CONCLUSIONS

Laxity of spinal cord suspension ligaments and the associated spinal cord motion disorder are possible pathogenic factors for chronic neck pain and headache in patients with EDS but without radiologically proven CCI.

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.

Posterior atlantoaxial fusion: a comprehensive review of surgical techniques and relevant vascular anomalies

Posterior atlantoaxial fusion is an important surgical technique frequently used to treat various pathologies involving the cervical 1-2 joint. Since the beginning of the 20th century, various fusion techniques have been developed with improved safety profile, higher fusion rates, and superior clinical outcome. Despite the advancement of technology and surgical techniques, posterior C1-2 fusion is still a technically challenging procedure given the complex bony and neurovascular anatomy in the craniovertebral junction (CVJ). In addition, vascular anomalies in this region are not uncommon and can lead to devastating neurovascular complications if unrecognized. Thus, it is important for spine surgeons to be familiar with various posterior atlantoaxial fusion techniques along with a thorough knowledge of various vascular anomalies in the CVJ. Intimate knowledge of the various surgical techniques in combination with an appreciation for anatomical variances, allows the surgeon develop a customized surgical plan tailored to each patient's particular pathology and individual anatomy. In this article, we aim to provide a comprehensive review of existing posterior C1-2 fusion techniques along with a review of common vascular anomalies in the CVJ.

Human Dorsal Root Ganglia

Sensory neurons with cell bodies situated in dorsal root ganglia convey information from external or internal sites of the body such as actual or potential harm, temperature or muscle length to the central nervous system. In recent years, large investigative efforts have worked toward an understanding of different types of DRG neurons at transcriptional, translational, and functional levels. These studies most commonly rely on data obtained from laboratory animals. Human DRG, however, have received far less investigative focus over the last 30 years. Nevertheless, knowledge about human sensory neurons is critical for a translational research approach and future therapeutic development. This review aims to summarize both historical and emerging information about the size and location of human DRG, and highlight advances in the understanding of the neurochemical characteristics of human DRG neurons, in particular nociceptive neurons.

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.

Detethering of the C2 Nerve Root and Avoidance of Transection and Injury During C1 Screw Placement: A Cadaveric Feasibility Study

INTRODUCTION

Regional neurovascular structures must be avoided during invasive spine hardware placement. During C1 lateral mass screw placement, the C2 nerve root is put in harm's way. Therefore the current anatomic study was performed to identify techniques that might avoid such neural injury.

MATERIALS AND METHODS

On 10 cadaveric sides, dissection was carried down to the craniocervical junction. The C2 nerve root was identified, and its distal branches were traced out into the surrounding posterior cervical musculature. Once dissected, the nerve was displaced inferiorly away from the lateral mass of C1.

RESULTS

On all sides, the C2 nerve root could be easily detethered from surrounding tissues. On all sides, this allowed lateral mass screw placement without compression of the nerve.

CONCLUSION

On the basis of our cadaveric study, the C2 nerve root can be detethered enough at the level of the posterior lateral mass of C1 to avoid its injury during screw placement into this area.

C2 spondylotic radiculopathy: the nerve root impingement mechanism investigated by para-sagittal CT/MRI, dynamic rotational CT, intraoperative microscopic findings, and treated by microscopic posterior foraminotomy

PURPOSE

C2 radiculopathy is known to cause occipito-cervical pain, but their pathology is unclear because of its rarity and unique anatomy. In this paper, we investigated the mechanism of C2 radiculopathy that underwent microscopic cervical foraminotomies (MCF).

METHODS

Three cases with C2 radiculopathy treated by MCF were investigated retrospectively. The mean follow-up period was 24 months. Pre-operative symptoms, imaging studies including para-sagittal CT and MRI, rotational dynamic CT, and intraoperative findings were investigated.

RESULTS

There were 1 male and 2 females. The age of patients were ranged from 50 to 79 years. All cases had intractable occipito-cervical pain elicited by the cervical rotation. C2 nerve root block was temporally effective. There was unilateral spondylosis in symptomatic side without obvious atlatoaxial instability. Para-sagittal MRI and CT showed severe foraminal stenosis at C1-C2 due to the bony spur derived from the lateral atlanto-axial joints. In one case, dynamic rotational CT showed that the symptomatic foramen became narrower on rotational position. MCF was performed in all cases, and the C2 nerve root was impinged between the inferior edge of the C1 posterior arch and bony spur from the C1-C2 joint. After surgery, occipito-cervical pain disappeared.

CONCLUSION

This study demonstrated that mechanical impingement of the C2 nerve root is one of the causes of occipito-cervical pain and it was successfully treated by microscopic resection of the inferior edge of the C1 posterior arch. Para-sagittal CT and MRI, rotational dynamic CT, and nerve root block were effective for diagnosis.

C2 nerve dysfunction associated with C1 lateral mass screw fixation

The C1 lateral mass screw technique is widely used for atlantoaxial fixation. However, C2 nerve dysfunction may occur as a complication of this procedure, compromising the quality of life of affected patients. This is a review of the topic of C2 nerve dysfunction associated with C1 lateral mass screw fixation and related research developments. The C2 nerve root is located in the space bordered superiorly by the posterior arch of C1 , inferiorly by the C2 lamina, anteriorly by the lateral atlantoaxial joint capsule, and posteriorly by the anterior edge of the ligamentum flavum. Some surgeons suggest cutting the C2 nerve root during C1 lateral mass screw placement, whereas others prefer to preserve it. The incidence, clinical manifestations, causes, management, and prevention of C2 nerve dysfunction associated with C(1) lateral mass screw fixation are reviewed. Sacrifice of the C2 nerve root carries a high risk of postoperative numbness, whereas postoperative nerve dysfunction can occur when it has been preserved. Many surgeons have been working hard on minimizing the risk of postoperative C2 nerve dysfunction associated with C1 lateral mass screw fixation.

C2 nerve root on magnetic resonance imaging of occipital neuralgia

STUDY DESIGN

Review and grade the morphology of the C1-C2 neural foramina, from the MR images of patients who underwent C1-C2 spinal surgery, and determine the relationship with ON.

OBJECTIVE

To evaluate the feasibility of MRI for C1-C2 neural foramen evaluation with a new grading system and to correlate the C1-C2 neural foramen grade with ON.

SUMMARY OF BACKGROUND DATA

There have been no MRI studies of patients with and without ON in relation to C2 nerve root ganglion findings.

METHODS

Among the registry of 124 patients who underwent C1-C2 spinal surgery between July 2004 and May 2012 in Seoul National University Bundang Hospital, we enrolled 101 patients who had information about ON and a relevant preoperative cervical spine MR image. A total of 202 neural foramina were evaluated with our new C1-C2 neural foramen grading system (grade, 0-3) using consensus reading by 2 experienced radiologists who were blinded to the clinical information. The relationship between the C1-C2 grading system and ON was assessed using a χ test and Fisher exact test. Inter- and intraobserver reliability agreement was assessed using the κ statistic.

RESULTS

All C1-C2 neural foramina were delineated on T2 parasagittal images. Among 202 C1-C2 neural foramina, grade zero was found in 49 foramina (24.3%), grade 1 in 95 (47.0%), grade 2 in 30 (14.9%), and grade 3 in 28 (13.9%). Grade 1 stenosis was most frequently noted. The grade 2 group had the most frequent prevalence of ON (43.3%), followed by grade 3 (35.7%), grade zero (30.6%), and grade 1 (29.5%). However, the relationship between the grade and ON was not statistically significant. Inter- and intraobserver agreements were substantially high.

CONCLUSION

C1-C2 neural foramina can be depicted on MR image. However, the relationship between the new grading system for C1-C2 neural foramina and ON was not statistically significant.

LEVEL OF EVIDENCE

4.

Computerized tomographic morphometric analysis of the cervical spine

Background:

Detailed knowledge of cervical canal and transverse foramens’ morphometry is critical for understanding the pathology of certain diseases and for proper preoperative planning. Lateral x-rays do not provide the necessary accuracy. A retrospective morphometric study of the cervical canal was performed at the authors’ institution to measure mean dimensions of sagittal canal diameter (SCD), right and left transverse foramens’ sagittal (SFD) and transverse (TFD) diameters and minimum distance between spinal canal and transverse foramens (dSC-TF) for each level of the cervical spine from C1-C7, using computerized tomographic scans, in 100 patients from the archives of the Emergency Room.

Results:

Significant differences for SCD were detected between C1 and the other levels of the cervical spine for both male and female patients. For the transverse foramen, significant differences in sagittal diameters were detected at C3, C4, C5 levels. For transverse diameters, significant differences at C3 and C4 levels. A significant difference of the distance between the transverse spinal foramen and the cervical canal was measured between left and right side at the level of C3. This difference was equally observed to male and female subjects.

Conclusion:

CT scan can replace older conventional radiography techniques by providing more accurate measurements on anatomical elements of the cervical spine that could facilitate diagnosis and preoperative planning, thus avoiding possible trauma to the vertebral arteries during tissue dissection and instrument application.

C2-fractures: part II. A morphometrical analysis of computerized atlantoaxial motion, anatomical alignment and related clinical outcomes

Knowledge on the outcome of C2-fractures is founded on heterogenous samples with cross-sectional outcome assessment focusing on union rates, complications and technical concerns related to surgical treatment. Reproducible clinical and functional outcome assessments are scant. Validated generic and disease specific outcome measures were rarely applied. Therefore, the aim of the current study is to investigate the radiographic, functional and clinical outcome of a patient sample with C2-fractures. Out of a consecutive series of 121 patients with C2 fractures, 44 met strict inclusion criteria and 35 patients with C2-fractures treated either nonsurgically or surgically with motion-preserving techniques were surveyed. Outcome analysis included validated measures (SF-36, NPDI, CSOQ), and a functional CT-scanning protocol for the evaluation of C1-2 rotation and alignment. Mean follow-up was 64 months and mean age of patients was 52 years. Classification of C2-fractures at injury was performed using a detailed morphological description: 24 patients had odontoid fractures type II or III, 18 patients had fracture patterns involving the vertebral body and 11 included a dislocated or a burst lateral mass fracture. Thirty-one percent of patients were treated with a halo, 34% with a Philadelphia collar and 34% had anterior odontoid screw fixation. At follow-up mean atlantoaxial rotation in left and right head position was 20.2 degrees and 20.6 degrees, respectively. According to the classification system of posttreatment C2-alignment established by our group in part I of the C2-fracture study project, mean malunion score was 2.8 points. In 49% of patients the fractures healed in anatomical shape or with mild malalignment. In 51% fractures healed with moderate or severe malalignment. Self-rated outcome was excellent or good in 65% of patients and moderate or poor in 35%. The raw data of varying nuances allow for comparison in future benchmark studies and metaanalysis. Detailed investigation of C2-fracture morphology, posttreatment C2-alignment and atlantoaxial rotation allowed a unique outcome analysis that focused on the identification of risk factors for poor outcome and the interdependencies of outcome variables that should be addressed in studies on C2-fractures. We recognized that reduced rotation of C1-2 per se was not a concern for the patients. However, patients with worse clinical outcomes had reduced total neck rotation and rotation C1-2. In turn, C2-fractures, especially fractures affecting the lateral mass that healed with atlantoaxial deformity and malunion, had higher incidence of atlantoaxial degeneration and osteoarthritis. Patients with increased severity of C2-malunion and new onset atlantoaxial arthritis had worse clinical outcomes and significantly reduced rotation C1-2. The current study offers detailed insight into the radiographical, functional and clinical outcome of C2-fractures. It significantly adds to the understanding of C2-fractures.

Troublesome occipital neuralgia developed by c1-c2 harms construct

Recently, Harms and Melcher modified Goel's approach, the C1 lateral mass and C2 pedicle screw fixation, and the new technique is currently in favor among neurosurgeons. Comparing to the advantages of Harms construct, the disadvantages were not extensively investigated. We experienced a patient with severe occipital pain developed after the C1 lateral mass screw placement for the traumatic atlantoaxial instability. We reviewed literatures about Harms construct with focus on the occipital neuralgia as a postoperative complication and suggest here technical tips to avoid the troublesome pain.

Diagnosis and management of cervicogenic headache

Upper cervical pain and/or headaches originating from the C0 to C3 segments are pain-states that are commonly encountered in the clinic. The upper cervical spine anatomically and biomechanically differs from the lower cervical spine. Patients with upper cervical disorders fall into two clinical groups: (1) local cervical syndrome; and (2) cervicocephalic syndrome. Symptoms associated with various forms of both disorders often overlap, making diagnosis a great challenge. The recognition and categorization of specific provocation and limitation patterns lend to effective and accurate diagnosis of local cervical and cervicocephalic conditions.