Is atlantoaxial instability the cause of Chiari malformation? Outcome analysis of 65 patients treated by atlantoaxial fixation

Suture Repair in Endoscopic Surgery for Craniovertebral Junction

Objective

Endoscopic approaches to the craniovertebral junction (CVJ) have been established as viable and effective surgical treatments in the past decade. One of the major complications is leakage of the cerebrospinal fluid (CSF). This study aimed to investigate the efficacy and feasibility of suture closure at the nasopharyngeal mucosa upon durotomy.

Methods

A series of consecutive patients who underwent different endoscopic approaches to the CVJ were retrospectively reviewed. The pathologies, surgical corridors, neurological and functional outcomes, radiological evaluations, and complications were analyzed. Different strategies of repair for the intraoperative CSF leakage were described and compared.

Results

A total of 22 patients covering 13 years were analyzed. There were 12, 2, and 8 patients who underwent transnasal, transoral, and combined approaches, respectively. There were 8 patients (36.4%) who experienced intraoperative CSF leakage, and were grouped into 2: 4 in the nonsuture (NS) group and 4 in the suture-repaired (SR) group. The NS group had 3 (75%) persistent CSF leakages postoperation that caused 1 mortality, whereas patients of the SR group had only 1 minor CSF rhinorrhea that healed spontaneously within days.

Conclusion

In this series of 22 patients who required anterior endoscopic resection of pathologies at the CVJ, there was 1 (4.5%) serious complication related to CSF leakage. For patients who had no durotomy, the mucosal incision at the nasopharynx usually healed rapidly and there were few procedure-related complications. For patients with intraoperative CSF leakage, suture closure was technically challenging but could significantly lower the risks of postoperative complications.

A Review of a New Clinical Entity of 'Central Atlantoaxial Instability': Expanding Horizons of Craniovertebral Junction Surgery

The author discusses the novel form of central or axial atlantoaxial instability and analyses its clinical significance. High degree of clinical and radiological understanding of the region is mandatory to diagnose and then treat such atlantoaxial instability. Evaluation of alignment of facets of atlas and axis and observations on direct manipulation of facets of atlas and axis forms the basis of diagnosis. The treatment of clinical entities like basilar invagination, Chiari formation, syringomyelia and myelopathy related to cervical spinal degeneration, spinal deformities, ossified posterior longitudinal ligament, and Hirayama disease can be influenced by the understanding of central or axial atlantoaxial instability.

Change of Anatomical Location of the Internal Carotid Artery Relative to the Atlas with Congenital Occipitalization and the Relevant Clinical Implications

INTRODUCTION

The occipitalization of the atlas (OA) is always associated with multiplanar dislocation and olisthy of the C1 over C2 facets, which may change the anatomical relationship between the internal carotid artery (ICA) and the atlas. The purpose of this current study is to identify the location of the ICA relative to the anterior aspect of the atlas in patients with OA and define the clinical implications for screw placement.

METHODS

We retrospectively reviewed the computed tomography angiography data of 86 patients with OA and 86 control subjects. Several parameters were also measured to quantitatively evaluate the mutual relationship.

RESULTS

In the OA group, 25.6% of ICAs were located in area 3 and 74.4% in area 2, whereas the percentages were 57.4% and 42.6%, respectively, in the control group. There were 73 (42.4%) ICAs in which the shortest distance between the dorsal surface of the ICA and the ventral cortex of the atlas was less than 4 mm in the OA group and only 50 (29.1%) in the control group. The ideal angulation of C1 screw trajectory was about 5 degrees more medial in the OA group than that in the control group (P < 0.01).

CONCLUSIONS

The risk of ICA injury is much higher in OA patients than in non-OA patients during the C1 screw placement. A mean medial angulation about 20 degrees will permit a long and safe screw purchase, but should be individualized. We recommend careful preoperative computed tomography angiography evaluation in all patients before surgery.

Can the Etiopathogenesis of Chiari Malformation Be Craniocervical Junction Stabilization Difference? Morphometric Analysis of Craniocervical Junction Ligaments

OBJECTIVE

The craniocervical junction permits a certain amount of mobility for the cervical spine. The biomechanical properties of occipital bone-atlas joint mainly depend on the bony structure, and atlas-axis joint biomechanical properties mainly depend on ligamentous structure. The underlying etiologic factor of Chiari malformation (CM) is debatable. Nowadays, some researchers argue that stabilization difference is one of the suspicious factors for etiopathogenesis. We aim to analyze the ligamentous morphometric differences of CM.

METHODS

Magnetic resonance images of 93 adult healthy subjects (n = 93) without any craniocervical junction development abnormalities and 25 (n = 25) adult patients with craniocervical junction development abnormalities (Arnold CM) were evaluated. Length, width, and length-width ratios of ligaments were evaluated.

RESULTS

Length of transverse ligament (mean: 23 ± 3.6 [range: 12.1-31.4]) in the normal population was significantly longer than transverse ligament length in CM patients (mean: 21.3 ± 2.5 [range: 17.2-24.9]). Length of alar ligament (mean: 10.7 ± 2 [range: 5.1-15.4]) in the normal population was significantly longer than alar ligament length in CM patients (mean: 8.8 ± 3.8 [range: 1.1-16.6]) (P = 0.007).

CONCLUSIONS

Craniocervical ligaments play an important role in maintaining stability and motion capacity of this region. This study promoted better understanding of craniocervical junction anomalies and provided data that facilitate performing more precise surgical treatment.

[Anterior stabilization of the CI-CIII vertebrae after transoral removal of an aggressive aneurysmal bone cyst of the CII vertebra (a case report and literature review)]

Treatment of patients with atlantoaxial instability caused by various diseases of the skull base and craniovertebral junction combined with ventral compression of the brainstem is a complex issue that is ambiguously resolved in different ways. We present a case of stepped treatment, the most important component of which was successful transoral removal of an aggressive aneurysmal bone cyst of the CII vertebra with anterior CI-CIII segment stabilization using an individual system, which was performed through the same approach.

CLINICAL CASE

A 31-year-old male patient presented with destruction of the CII body and odontoid process affected by an aggressive aneurysmal bone cyst causing disintegration of the CII posterior wall and odontoid process, which clinically manifested by constricted motion and pain in the cervical spine.

RESULTS

Three-step surgical treatment was performed. First, we performed a puncture biopsy of the CII body through the submandibular approach as well as posterior occipitospondylodesis with metal instrumentation from the occipital bone level to the CIV vertebra. Two months later, the patient underwent transoral removal of the CII body and odontoid process lesion and anterior CI-CIII segment stabilization using an individual cover metal system through the same approach. Two weeks after the second intervention, the occipitospondylodesis was transformed to a posterior CI-CIII stabilization system. Control CT 8 months after surgery showed the correct position of both stabilization systems.

CONCLUSION

The use of individual instrumentation for anterior stabilization of the CI-CIII vertebrae in various diseases of the craniovertebral junction area is an effective and promising technique.

Basilar invagination associated with chiari malformation type I: A literature review

Basilar invagination (BI) and Chiari malformation type I (CM-I) are very important anomalies that introduce instability and compression in the occipitocervical transition region and have complex clinical characteristics. These anomalies vary according to the affected structures. The present study revises current knowledge regarding the anatomy, anatomo-physiology, clinical manifestations, and radiological findings of these entities and the associated surgical treatment approaches. A bibliographic survey was performed through a search in the Medline, PubMed, SciELO, Science and LILACS databases. When associated, these craniovertebral malformations result in neurological deficits due to neural parenchyma compression; however, the presence of microtraumas due to repetitive lesions caused by the bulb and cervical marrow instability has been highlighted as a determinant dysfunction. Surgical treatment is controversial and has many technical variations. Surgery is also challenging due to the complex anatomical characteristics and biomechanics of this region. Nevertheless, advances have been achieved in our understanding of related mechanisms, and compression and atlantoaxial instability are considered key elements when selecting the surgical approach.

Revision for Failed Craniovertebral Junction Stabilization: A Report of 30 Treated Cases

OBJECTIVE

To analyze the probable causes of failed craniovertebral junction stabilization procedures, and to evaluate the advantages of the Goel technique in revision surgery and the positive factors that lead to reduction of the instability and achieve ultimate arthrodesis.

METHODS

During the period from January 2010 to June 2018, we treated 30 cases where previous attempt at craniovertebral stabilization with various fixation techniques had failed and the patients presented with progressively worsening neurologic deficits. All patients were re-operated by lateral mass fixation techniques described by the senior author. The technique involved opening of the atlantoaxial joint, denuding the articular cartilage, introduction of bone graft within the articular cavity, and plate and screw fixation. No bone decompression was done.

RESULTS

Fixation of multiple subaxial spinal segments (n = 9), inclusion of occipital bone in the fixation construct (n = 21), and dependence on metal stabilization rather than bone fusion (n = 19) appear to be important causes of implant failure. All patients improved in clinical symptoms after revision surgery. Postoperative images of all patients demonstrated significant reduction of the atlantoaxial dislocation and craniovertebral junction realignment. During the average follow-up period of 32 months, all reoperated patients continued to show clinical recovery. No further surgery was necessary.

CONCLUSIONS

Although relatively difficult, when indicated, reoperation and direct stabilization of the atlantoaxial joint can result in significant and enduring clinical recovery.

Foramen magnum decompression without bone removal: C1-C2 posterior fixation for Chiari with congenital atlantoaxial dislocation/basilar invagination

Background:

Atlantoaxial dislocation (AAD) and basilar invagination (BI) may coexist with Chiari malformations (CM) and a small posterior fossa volume. These are typically treated with craniovertebral junction fusion and foramen magnum decompression (FMD). Here, we evaluated whether C1–C2 posterior reduction and fixation (which possibly opens up the ventral foramen magnum) would effectively treat AAD and CM without additionally performing FMD.

Methods:

This is a retrospective analysis of 38 patients with BI, AAD, and CM who underwent C1–C2 posterior reduction and fusion without FMD. Baseline and follow-up clinical, demographic, and radiological data were evaluated.

Results:

The vast majority of patients (91.9%) improved both clinically and radiographically following C1–C2 fixation alone; none later required direct FMD. Notably, AAD was irreducible in 25 (65.8%) patients. Preoperatively, syringomyelia was present in 28 (73.7%) patients and showed resolution. In 3 (8.1%) patients, resolution of syrinxes did not translate into clinical improvement. Of interest, 5 patients who sustained inadvertent dural lacerations exhibited transient postoperative neurological worsening.

Conclusions:

Posterior C1–C2 distraction and fusion alone effectively treated AAD, BI, accompanied by CM. The procedure sufficiently distracted the dens, reversed dural tenting, and restored the posterior fossa volume while relieving ventral brainstem compression making FMD unnecessary. Surgeons should, however, be aware that inadvertent dural lacerations might contribute to unwanted neurological deterioration.

Atlantoaxial Instability: Evolving Understanding

The atlantoaxial joint is the most mobile joint in the body. The physical architecture of the joint is characterized by a uniformly round and approximately flat surface, which allows a wide range of unobstructed movements. The standing human posture and lifelong heartbeat like uninterrupted activity of the atlantoaxial joint, and its ability to facilitate saying both 'yes' and 'no' necessarily requires smooth and 'fluid' movements that are supported by strong yet supple ligaments. The magnificent architectural structure that is 'magically' designed and carved by nature to provide both stability and mobility and to allow a smooth and safe transit passage for the most critical neural and vascular structures can only be admired in awe and appreciated.

Role of Subaxial Spinal and Atlantoaxial Instability in Multisegmental Cervical Spondylotic Myelopathy

AIM

In this paper the role of atlantoaxial and multilevel subaxial spinal instability as the primary nodal point of the pathogenesis of degenerative cervical spinal disease-related myelopathy, and the focus of surgical treatment for it, is evaluated.

MATERIALS AND METHODS

The series analyses the treatment of 73 patients with single or multilevel degenerative cervical spinal disease by fixation of the involved spinal segment(s) alone, aimed at arthrodesis. No bone decompression or disc/osteophyte resection was done. In 23 patients, the atlantoaxial joint was included in the spinal fixation, as atlantoaxial instability was identified by facetal malalignment on imaging or by observations on direct bone manipulation during surgery. There were 70 males and 3 females. The ages of the patients ranged from 35 to 76 years (average 57 years). The transarticular screw method was deployed for subaxial spinal fixation and a lateral mass plate/rod and screw technique was used for atlantoaxial fixation.

RESULTS

During the follow-up period, which ranged from 3 to 42 months (average 27 months), all patients improved in terms of their clinical symptoms. There were no surgery- or implant-related complications.

CONCLUSION

Atlantoaxial joint instability is frequently associated with subaxial multilevel spinal instability in degenerative spinal disease. Fixation of the spinal segments provides a safe, effective and rational treatment for single or multilevel spinal degeneration.

Chiari Malformations

BACKGROUND

Chiari malformations (CM) represent a group of anomalies characterized by descent of the cerebellar tonsils or vermis into the cervical spinal canal. These malformations can be associated with abnormalities such as hydrocephalus, spina bifida, hydromyelia, syringomyelia, curvature of the spine (kyphosis and scoliosis) and tethered cord syndrome. Hereditary syndromes and other disorders that affect growth and bone formation-such as craniosynostosis, Ehlers-Danlos syndromes and Klippel-Feil syndrome-can also be associated with CM.

METHODS

The literature concerning treatment is large, and an extensive range of therapeutic protocols have been described. The literature is inclined in favour of surgery; however, there is controversy over when to perform surgery and which procedure is most appropriate. Lately, the indications for stabilization have been under discussion.

RESULTS AND CONCLUSION

In this paper we review the literature and discuss the historical background, anatomical forms, pathophysiology, clinical presentation, relationships with other diseases and diagnostic procedures for these abnormalities.

Cervical Fusion as a Protective Response to Craniovertebral Junction Instability: A Novel Concept

The author reviews the various types of cervical fusion that are associated with instability of the craniovertebral junction. Assimilation of the atlas, C2-3 fusion, the Klippel-Feil abnormality, and pancervical fusion are amongst the more common types of bone abnormalities. It is conceptualised that these types of cervical fusion are not related to any kind of embryological dysgenesis or fault, but instead emerge due to longstanding muscle spasms of the neck in response to atlantoaxial instability. Such bone fusions could be secondary protective responses to longstanding atlantoaxial instability.

Central or Axial Atlantoaxial Dislocation as a Cause of Cervical Myelopathy: A Report of Outcome of 5 Cases Treated by Atlantoaxial Stabilization

OBJECTIVE

The implications of diagnosis and treatment of central or axial atlantoaxial dislocation (CAAD) as a cause of symptoms of cervical myelopathy are evaluated.

METHODS

This is a report of a series of 5 patients who presented with the primary symptoms of spasticity and motor weakness and paresthesias in all the limbs. There was no evidence of any significant compression of the dural tube or neural structures at the craniovertebral junction. There was no craniovertebral junction instability when assessed by classically described radiologic parameters. CAAD was diagnosed based on our recently discussed parameter of facetal alignment, corroborative clinical and radiologic evidence, and direct observation of atlantoaxial instability by manual manipulation of the bones of the region. All patients underwent atlantoaxial fixation.

RESULTS

There was remarkable improvement in the clinical symptoms in the immediate postoperative period and during the follow-up period of 12-24 months (average, 16 months). All patients have continued to have progressive clinical recovery. Clinical assessments were done using Goel clinical evaluation scale, Japanese Orthopedic Association score, and visual analog scale.

CONCLUSIONS

Identification and treatment of CAAD can have a significant management impact on patients where the cause of spastic quadriparesis is otherwise undiagnosed.

Delayed neurological deterioration following atlantoaxial facet joint distraction and fixation in a patient with Chiari malformation type I

Chiari malformation type I (CM-I) is typically treated with foramen magnum decompression. However, a recent study proposed a new technique for patients with CM-I, wherein only short atlantoaxial joint fusion and distraction is applied. Posterior fusion with or without atlantoaxial distraction is a potential option for patients with CM-I associated with basilar invagination or complex anomalous bony craniovertebral junction pathology, since this procedure allows clinicians to avoid using the technically demanding transoral approach in which some or all of the odontoid tip is invisible. Distraction of the atlantoaxial joint reduces ventral cervicomedullary compression, leading to neurological improvement. Here, the authors report the case of a 50-year-old woman with CM-I plus basilar invagination whose condition immediately improved but then gradually deteriorated following atlantoaxial joint distraction and fusion. Therefore, the authors performed endonasal/transoral odontoidectomy, which resulted in prolonged neurological recovery. Short atlantoaxial fusion with distraction is a smart and ideal surgical planning concept that can result in significant neurological improvement. However, this case suggests that anterior odontoidectomy is still an essential element of the intervention strategy for patients with CM-I with complex craniovertebral junction pathology.

C1-2 and C2-3 Instability in the Presence of Hypoplastic Posterior Elements of C2 Vertebra: Report of 2 Cases

BACKGROUND

We present 2 cases involving a previously unreported clinical situation in which basilar invagination, atlantoaxial instability, and C2-3 instability were associated with a bifid posterior arch of the axis bone.

CASE DESCRIPTIONS

Two young males presented with limb weakness, spasticity, and paresthesias. Both patients had altered voice quality, with reduced and thin volume, and difficulty sleeping supine. Radiologic imaging showed an absence of the posterior elements of the C2 vertebrae. The C3 spinous process mimicked the C2 spinous process in shape and size. C1-2 and C2-3 posterior fixations were performed.

CONCLUSIONS

C1-2 and C2-3 fixation resulted in firm fixation of the region and a remarkable clinical recovery. The most significant features were an immediate postoperative improvement in voice quality and the ability to sleep comfortably in the supine position.

Chiari I malformation: surgical technique, indications and limits

BACKGROUND

Chiari malformation type I (CM-I) is a rare disease characterised by herniation of cerebellar tonsils below the foramen magnum with associated anomalies of posterior fossa. We describe here the surgical technique, indications and limits of surgical treatment.

METHOD

The authors describe the surgical technique, including: posterior fossa decompression, opening of the foramen of Magendie and duraplasty in case of CM-I.

CONCLUSIONS

Posterior fossa decompression plus duraplasty is a safe and effective procedure for patients with CM-I malformation.

Chiari malformation: Has the dilemma ended?

Chiari malformation as a clinical entity has been described more than hundred years ago. The concepts regarding pathogenesis, clinical features and management options have not yet conclusively evolved. Considering that a variety of treatment methods are being adopted to treat Chiari malformation is suggestive of the fact that confusion still reigns supreme in the minds of treating clinicians. Over the years, the understanding of Chiari malformation has changed from a disease process to a natural protective phenomenon and the treatment from decompression to fixation.

Pediatric Craniovertebral Junction Surgery

The craniovertebral junction (CVJ) has attracted more attention in pediatric medicine in recent years due to the progress in surgical technologies allowing a direct approach to the CVJ in children. The CVJ is the site of numerous pathologies, most originating in bone anomalies resulting from abnormal CVJ development. Before discussing the surgical approaches to CVJ, three points should be borne in mind: first, that developmental anatomy demonstrates age-dependent mechanisms and the pathophysiology of pediatric CVJ anomalies; second, that CT-based dynamic simulations have improved our knowledge of functional anatomy, enabling us to locate CVJ lesions with greater certainty; and third, understanding the complex structure of the pediatric CVJ also clarifies the surgical anatomy. This review begins with a description of the embryonic developmental process of the CVJ, comprising ossification and resegmentation of the somite. From the clinical perspective, pediatric CVJ lesions can be divided into three categories: developmental bony anomalies with or without instability, stenotic CVJ lesions, and others. After discussing surgery and management based on this classification, the author describes surgical outcomes on his hands, and finally proceeds to address controversial issues specific for pediatric CVJ surgery. The lessons, which the author has gleaned from his experience in pediatric CVJ surgery, are also presented briefly in this review. Recent technological progress has facilitated pediatric surgery of the CVJ. However, it is important to recognize that we are still far from reliably and consistently obtaining satisfactory results. Further progress in this area awaits contributions of the coming generations of pediatric surgeons.

Multilevel Spinal Segmental Fixation for Kyphotic Cervical Spinal Deformity in Pediatric Age Group-Report of Management in 2 Cases

OBJECTIVE

We discuss the role of instability of multiple spinal segments including the atlantoaxial joint in the pathogenesis of cervical kyphotic deformity.

MATERIAL AND METHODS

Two male patients (5 and 17 years old) had severe cervical kyphosis and presented with symptoms related to myelopathy. The patients underwent multisegmental spinal distraction and fixation that included atlantoaxial joint. No bone decompression was done.

RESULTS

At a follow-up of >30 months, both patients had significant neurologic recovery. Investigations at follow-up showed successful arthrodesis of treated spinal segments. Although incomplete, there was recovery in kyphosis.

CONCLUSIONS

Multisegmental spinal distraction and fixation can lead to reduction in kyphosis and relief from symptoms related to myelopathy. Role of spinal instability in general and atlantoaxial joint instability in particular in pathogenesis of cervical kyphosis need to be assessed on the basis of studies with a larger number of patients.

Role of Atlantoaxial and Subaxial Spinal Instability in Pathogenesis of Spinal "Degeneration"-Related Cervical Kyphosis

BACKGROUNDS

The role of subaxial and atlantoaxial instability in the pathogenesis of "degeneration"-related cervical kyphosis is evaluated.

MATERIAL AND METHODS

During the period 2013-2016, the authors treated 21 patients having cervical kyphosis that was related to degenerative spinal disease. The patients presented with symptoms related to cervical myelopathy. Kyphosis was diagnosed on the basis of described radiologic parameters. The patients were divided into 3 groups. Group A (10 patients) had manifest radiologic evidence of atlantoaxial dislocation, type 1 facetal instability, abnormal increase in atlantodental interval, and evidence of cord compression by the odontoid process. Group B (5 patients) had axial or central atlantoaxial facetal instability (type 2 or 3 atlantoaxial facetal instability) and subaxial spinal instability. Group C (6 patients) had subaxial spinal instability. The patients were treated by only stabilization. Group A patients underwent atlantoaxial fixation, group B patients underwent atlantoaxial and subaxial fixation, and group C patients underwent only subaxial spinal fixation. The operation was aimed at arthrodesis of the spinal segments. No bone or soft tissue decompression was done.

RESULTS

During the minimum follow-up period of 6 months, all patients improved in their neurologic symptoms and demonstrated evidence of spinal arthrodesis. There were no major surgical complications.

CONCLUSIONS

Spinal instability plays a major role in the generation of cervical spinal kyphosis. Atlantoaxial instability may form the primary and nodal site of development of the process of spinal degeneration in general and kyphosis in particular.

Trends in surgical treatment of Chiari malformation Type I in the United States

OBJECTIVE The goal of this analysis was to define temporal and geographic trends in the surgical treatment of Chiari malformation Type I (CM-I) in a large, privately insured health care network. METHODS The authors examined de-identified insurance claims data from a large, privately insured health care network of over 58 million beneficiaries throughout the United States for the period between 2001 and 2014 for all patients undergoing surgical treatment of CM-I. Using a combination of International Classification of Diseases (ICD) diagnosis codes and Current Procedural Terminology (CPT) codes, the authors identified CM-I and associated diagnoses and procedures over a 14-year period, highlighting temporal and geographic trends in the performance of CM-I decompression (CMD) surgery as well as commonly associated procedures. RESULTS There were 2434 surgical procedures performed for CMD among the beneficiaries during the 14-year interval; 34% were performed in patients younger than 20 years of age. The rate of CMD increased 51% from the first half to the second half of the study period among younger patients (p < 0.001) and increased 28% among adult patients between 20 and 65 years of age (p < 0.001). A large sex difference was noted among adult patients; 78% of adult patients undergoing CMD were female compared with only 53% of the children. Pediatric patients undergoing CMD were more likely to be white with a higher household net worth. Regional variability was identified among rates of CMD as well. The average annual rate of surgery ranged from 0.8 surgeries per 100,000 insured person-years in the Pacific census division to 2.0 surgeries per 100,000 insured person-years in the East South Central census division. CONCLUSIONS Analysis of a large nationwide health care network showed recently increasing rates of CMD in children and adults over the past 14 years.

Treatment of "idiopathic" syrinx by atlantoaxial fixation: Report of an experience with nine cases

Objective:

The authors evaluate the significance of atlantoaxial instability in the management of idiopathic syringomyelia.

Background:

We recently observed that atlantoaxial dislocation can be present even when the atlantodental interval was within normal range. Atlantoaxial instability can be identified on the basis of facetal mal-alignment or even by direct observation of status of joint during surgery. Our observations are discussed in nine patients where we identified and treated atlantoaxial instability in cases that would otherwise be considered as having “idiopathic” syrinx.

Materials and Methods:

The authors report experience with nine cases that were diagnosed to have “idiopathic” syrinx. The main bulk of the syrinx was located in the cervico-dorsal spinal region in all cases. One patient had been treated earlier by syringo-subarachnoid shunt surgery and one patient had undergone foramen magnum decompression.

Results:

On radiological evaluation, eight patients had posterior atlantoaxial facetal (Type B) dislocation. In one patient there was no facetal mal-alignment and was labeled to have axial or central (Type C) facetal instability. All patients were treated by atlantoaxial fixation. All patients improved symptomatically in the immediate postoperative period and the improvement was progressive and sustained on follow-up. In one case, the size of syrinx reduced in the immediate postoperative imaging. In the period of follow-up (range 6–42 months - average 19 months), reduction in the size of syrinx was demonstrated on imaging in three cases.

Conclusions:

The positive clinical outcome suggests that atlantoaxial instability may be the defining phenomenon in development of previously considered “idiopathic” syringomyelia.

Craniocervical spinal instability after type 1 Arnold Chiari decompression: a case report

To present and describe an unusual case of spinal instability after craniocervical spinal decompression for a type-1 Chiari malformation. Type-1 Chiari malformation is a craniocervical disorder characterized by tonsillar displacement greater than 5 mm into the vertebral canal; posterior fossa decompression is the most common surgical treatment for this condition. Postoperative complications have been described: cerebrospinal fluid leak, pseudomeningocele, aseptic meningitis, wound infection, and neurological deficit. However, instability after decompression is unusual. A 9-year-old female presented with symptomatic torticollis after cervical decompression for a type-1 Chiari malformation. Spinal instability was diagnosed; craniocervical stabilization was performed. After a 12-month follow-up, spinal stability was achieved, with a satisfactory clinical neck alignment. We present a craniocervical instability secondary to surgical decompression; clinical and radiological symptoms, and definitive treatment were described.