Surgical Treatment of Chiari I Malformation

Chiari Malformation Type 1 in Adults

The term Chiari malformation refers to a heterogeneous group of anatomical abnormalities at the craniovertebral junction. Chiari malformation type 1 (CM1) refers to the abnormal protrusion of cerebellar tonsils through the foramen magnum and is by far the commonest type. Its prevalence is estimated approximately 1%; it is more common in women and is associated with syringomyelia in 25-70% of cases. The prevalent pathophysiological theory proposes a morphological mismatch between a small posterior cranial fossa and a normally developed hindbrain that results in ectopia of the tonsils.In most people, CM1 is asymptomatic and diagnosed incidentally. In symptomatic cases, headache is the cardinal symptom. The typical headache is induced by Valsalva-like maneuvers. Many of the other symptoms are nonspecific, and in the absence of syringomyelia, the natural history is benign. Syringomyelia manifests with spinal cord dysfunction of varying severity. The approach to patients with CM1 should be multidisciplinary, and the first step in the management is phenotyping the symptoms, because they may be due to other pathologies, like a primary headache syndrome. Magnetic resonance imaging, which shows cerebellar tonsillar decent 5 mm or more below the foramen magnum, is the gold standard investigative modality. The diagnostic workup may include dynamic imaging of the craniocervical junction and intracranial pressure monitoring.The management of CM1 is variable and sometimes controversial. Surgery is usually reserved for patients with disabling headaches or neurological deficits from the syrinx. Surgical decompression of the craniocervical junction is the most widely used procedure. Several surgical techniques have been proposed, but there is no consensus on the best treatment strategy, mainly due to lack of high-quality evidence. The management of the condition during pregnancy, restriction to lifestyle related to athletic activities, and the coexistence of hypermobility require special considerations.

Evaluation of Adult and Pediatric Chiari Type 1 Malformation Patients: Do Consensus Documents Fit Everyday Practice?

The management of Chiari 1 malformation (CM1) and Syringomyelia (Syr) has shown many changes in surgical indications and techniques over time. The dedicated neurosurgical and neurological community recently planned to analyze the state of the art and find conduct uniformity. This led to international consensus documents on diagnostic criteria and therapeutic strategies. We aimed to evaluate, in a large, monocentric surgical series of adult and children CM1 patients, if the daily clinical practice reflects the consensus documents. Our series comprises 190 pediatric and 220 adult Chiari patients submitted to surgery from 2000 to 2021. The main indications for the treatment were the presence of Syr and symptoms related to CM1. While there is great correspondence with the statements derived from the consensus documents about what to do for Syr and symptomatic CM1, the accordance is less evident in CM1 associated with craniosynostosis or hydrocephalus, especially when considering the early part of the series. However, we think that performing such studies could increase the homogeneity of surgical series, find a common way to evaluate long-term outcomes, and reinforce the comparability of different strategies adopted in different referral centers.

Occipitocervical fusion as treatment of instability in Chiari malformation

Introduction. Occipitocervical (OC) fusion is a method for fixation of the OC junction when there is instability of that segment. Arnold Chiari malformation is a congenital disorder where cerebellar tonsils descend through the foramen magnum, which can lead to cervicomedular compression and formation of syrinx. While treating this condition, for the purpose of decompression, the foramen magnum is expanded which can potentially harm the stability of the OC junction. Case outline. We are presenting the case of a 16 year old female who was surgically treated (suboccipital craniectomy and decompression) because of Arnold Chiari malformation type I. One-year post-op multislice computed tomography verified a slight enlargement of basion-axial and basion-dens intervals, with signs of spinal cord compression. Surgery was performed - occipitocervical fusion, canal decompression on C1 and C2 levels with a plate on occipital bone and screws placed in the third, fourth, and fifth cervical vertebra. Conclusion. Occipitocervical fusion is a complex surgical procedure (vital neurovascular structures), but it is a reliable method for treatment of instability of the OC junction.

Dorsal Atlantoaxial Ligament Hypertrophy as a Cause for Clinical Signs in Dogs with Dens Abnormalities

The objective of this study is to suggest clinical and subclinical atlantoaxial (AA) instability as a cause for dorsal AA ligament hypertrophy responsible for clinical signs in dogs with dens abnormalities. Clinical information from five dogs with malformed dens and dorsal spinal cord compression at the AA junction was collected. All dogs had neck pain, associated with tetraparesis in three cases. Radiological examination revealed hypoplastic dens in two dogs and a defect in its ossification in the other three. Stress views were able to demonstrate obvious AA instability only in two cases, but it was suspected in the other owing to response to surgical fixation of the joint and the presence of a dorsal compressive band, which was considered an enlarged dorsal AA ligament. Surgical and histopathological examination of compressive tissue confirmed hypertrophy of the ligament. Long-term prognosis in the four operated cases, either by dorsal decompression and ventral fixation or by ventral fixation alone, was excellent. A malformed dens can cause subclinical instability, unnoted in dynamic studies. As instability may lead to hypertrophy of joint ligaments, soft tissue changes (specifically dorsal AA ligament hypertrophy) points out this instability and the need for joint fixation if surgical management is required.

Long-term outcomes of surgical management in subtypes of Chiari malformation

Objective: Chiari malformations (CMs) are a heterogeneous group of disorders defined by anatomic anomalies of the cerebellum, brainstem, and craniovertebral junction (CVJ). The aims of this study are to establish the demographic and clinical features, incidence, surgical procedures, and outcomes in large series of old and new subtypes of CMs.Material and Methods: All patients were evaluated and operated on for CM-0, 1, and 1.5 between 1985 and 2016. The patients were grouped into various subtypes. Demographic data, additional diseases, clinical features, surgical procedures, complications and outcomes were recorded.Results: 191 patients who underwent various surgical procedures were evaluated. Their mean age was 37.21 ± 9.89. We detected 15 cases of CM-0 (7.8%), 121 cases of CM-1 (63.4%), 55 cases of CM-1.5 (28.8%). In total there were 191 cases, and 220 surgical procedures were performed. 29 (13.2%) of all surgical procedure was reoperations and secondary operations. SM Cyst is found to be decreased in 72 (76.5%) patients, unchanged in 14 (14.8%) and increased in 8(8.5%) of 94 patients radiologically. Clinical outcomes are better for 131 (65.8%), same for 31 (16.2%) and worse for 9 (15%).Conclusion: This study with 172 patients is a large series that includes CM-0, 1, and 1.5 subtypes. CM-1.5 also differs for symptom presentation and durations from CM-1. There are more neurological abnormalities in patients with SM. CVD alone are an effective, useful and safe surgical procedure for CM-0, CM-1 and CM-1.5. Surgical procedure, SM existence, and symptom duration have powerful effects on outcomes.

Intradural Pathology Causing Cerebrospinal Fluid Obstruction in Syringomyelia and Effectiveness of Foramen Magnum and Foramen of Magendie Dredging Treatment

OBJECTIVE

This article discusses the procedure of foramina magnum and Magendie dredging, summarizing the pathologic changes in the intradural region of the craniocervical junction in patients with syringomyelia and the pathophysiologic mechanism of cerebrospinal fluid (CSF) circulation obstruction.

METHODS

Clinical data from 50 adult patients with syringomyelia treated at Xuanwu Hospital from July 2018 to January 2019 were collected and retrospectively analyzed. All operations were performed with foramina magnum and Magendie dredging, and all intradural factors that may have induced the obstruction of CSF circulation were recorded.

RESULTS

Intradural pathology was found in all patients. The pathologic changes that may have caused obstruction of the CSF circulation include tonsil occupying the foramen magnum and overlying foramen of Magendie in 88% (44/50), intertonsillar arachnoid adhesions in 36% (18/50), tonsil to medulla arachnoid adhesions in 18% (9/50), medialized tonsils in 70% (35/50), vermian branch of posterior inferior cerebellar artery in 22% (11/50), arachnoid veil in 16% (8/50), cisterna magna cyst in 4% (2/50), and tonsil to dura mater arachnoid adhesions in 8% (4/50). Mean duration of follow-up was 13.3 months. The long-term effective rate was 96.0%. Postoperative magnetic resonance imaging revealed that the size of the syringomyelia was reduced or completely resolved in 88% of patients. The mean preoperative Japanese Orthopaedic Association score was 12.9 ± 3.1, which improved to 14.7 ± 3.2 (P < 0.05) at last clinical follow-up.

CONCLUSIONS

Intradural pathology that causes CSF circulation obstruction exists in many forms. Relieving the obstruction of the foramen magnum and foramen of Magendie is key to surgical treatment.

Spinal cord infarction with resultant paraplegia after Chiari I decompression: case report

Paraplegia after posterior fossa surgery is a rare and devastating complication. The authors reviewed a case of paraplegia following Chiari decompression and surveyed the literature to identify strategies to reduce the occurrence of such events.An obese 44-year-old woman had progressive left arm pain, weakness, and numbness and tussive headaches. MRI studies revealed a Chiari I malformation and a cervicothoracic syrinx. Immediately postoperatively after Chiari decompression the patient was paraplegic, with a T6 sensory level bilaterally. MRI studies revealed equivocal findings of epidural hematoma at the site of the Chiari decompression and in the upper thoracic region. Surgical exploration of the Chiari decompression site and upper thoracic laminectomies identified possible venous engorgement, but no hematoma. Subsequent imaging suggested a thoracic spinal cord infarction. Possible explanations for the spinal cord deficit included spinal cord ischemia related to venous engorgement from prolonged prone positioning in an obese patient in the chin-tucked position. At 6.5 years after surgery the patient had unchanged fixed motor and sensory deficits.Spinal cord infarction is rare after Chiari decompression, but the risk for this complication may be increased for obese patients positioned prone for extended periods of time. Standard precautions may be insufficient and intraoperative electrophysiological monitoring may need to be considered in these patients.

Development of Common Data Elements for Use in Chiari Malformation Type I Clinical Research: An NIH/NINDS Project

The management of Chiari I malformation (CMI) is controversial because treatment methods vary and treatment decisions rest on incomplete understanding of its complex symptom patterns, etiologies, and natural history. Validity of studies that attempt to compare treatment of CMI has been limited because of variable terminology and methods used to describe study subjects. The goal of this project was to standardize terminology and methods by developing a comprehensive set of Common Data Elements (CDEs), data definitions, case report forms (CRFs), and outcome measure recommendations for use in CMI clinical research, as part of the CDE project at the National Institute of Neurological Disorders and Stroke (NINDS) of the US National Institutes of Health. A working group, comprising over 30 experts, developed and identified CDEs, template CRFs, data dictionaries, and guidelines to aid investigators starting and conducting CMI clinical research studies. The recommendations were compiled, internally reviewed, and posted online for external public comment. In October 2016, version 1.0 of the CMI CDE recommendations became available on the NINDS CDE website. The recommendations span these domains: Core Demographics/Epidemiology; Presentation/Symptoms; Co-Morbidities/Genetics; Imaging; Treatment; and Outcome. Widespread use of CDEs could facilitate CMI clinical research trial design, data sharing, retrospective analyses, and consistent data sharing between CMI investigators around the world. Updating of CDEs will be necessary to keep them relevant and applicable to evolving research goals for understanding CMI and its treatment.

The Chiari I malformation

As with many pathologies, the course of our understanding of the Chiari I malformation (CIM) has developed extensively over time. The early descriptions of the Chiari malformations by Hans Chiari in 1891 opened the door for future classification and research on this topic. However, even over a long timeframe, our understanding of the pathophysiology and, more importantly, treatment, remained in its infancy. As recently as the 1970s, CIM was not discussed in popular neurology textbooks. Syringomyelia is listed as a degenerative disorder with no satisfactory treatment. Radiation therapy was considered an option in treatment, and surgery was thought to play no role. During the last 40 years, equivalent to the duration of a neurosurgical career, our understanding of the pathophysiology and natural history of CIM, coupled with modern MRI, has improved the treatment paradigm for this patient population. More importantly, it has given us evidence confirming that CIM is a disorder responsive to surgical intervention, giving patients once thought to be destined for lifelong disability a comparatively normal life after treatment. The purpose of this article is to offer a review of CIM and its important associated entities. The authors will discuss the evolution in understanding of the Chiari malformation and, importantly, distinguish between symptomatic CIM and asymptomatic tonsillar ectopia, based on imaging and presenting symptomatology. They will discuss techniques for surgical intervention, expected outcomes, and complications after surgery. Proper patient selection for surgery based on appropriate symptomatology is tantamount to achieving good surgical outcomes in this population, separating those who can be helped by surgery from those who are unlikely to improve. While our knowledge of the Chiari malformations continues to improve through the efforts of clinical and basic science researchers, surgeons, and patients, our current understanding of these entities represents a monumental improvement in patient care over a relatively short time period.

Heterotopic ossification following suboccipital craniectomy decompression surgery for Chiari malformation type I: case report

Suboccipital craniectomy with duraplasty is a commonly performed procedure for children with symptomatic Chiari malformation type I (CM-I). Several dural substitutes are used for duraplasty, ranging from pericranium to synthetic materials. When available, autologous pericranium is often preferred due to its low cost, performance in obtaining a watertight closure, ease of suturing, and absence of immune reaction. Long-term follow-up data on the durability of various dural substitutes are lacking. The authors report a rare, long-term complication of duraplasty performed using an autologous pericranial graft, and they conduct a literature review of similar complications. Heterotopic ossification of an autologous pericranial graft is a rare complication of duraplasty. This dystrophic bone growth can be symptomatic due to compression of neural structures, and it requires reoperation for removal. Surgeons should consider this rare long-term complication in patients presenting with unusual symptoms after duraplasty with pericranium.

Patients with "benign" Chiari I malformations require surgical decompression at a low rate

OBJECTIVE

There are sparse published data on the natural history of "benign" Chiari I malformation (CM-I)-i.e., Chiari with minimal or no symptoms at presentation and no imaging evidence of syrinx, hydrocephalus, or spinal cord signal abnormality. The purpose of this study was to review a large cohort of children with benign CM-I and to determine whether these children become symptomatic and require surgical treatment.

METHODS

Patients were identified from institutional outpatient records using International Classification of Diseases, 9th Revision, diagnosis codes for CM-I from 1996 to 2016. After review of the medical records, patients were excluded if they 1) did not have a diagnosis of CM-I, 2) were not evaluated by a neurosurgeon, 3) had previously undergone posterior fossa decompression, or 4) had imaging evidence of syringomyelia at their first appointment. To include only patients with benign Chiari (without syrinx or classic Chiari symptoms that could prompt immediate intervention), any patient who underwent decompression within 9 months of initial evaluation was excluded. After a detailed chart review, patients were excluded if they had classical Chiari malformation symptoms at presentation. The authors then determined what changes in the clinical picture prompted surgical treatment. Patients were excluded from the multivariate logistic regression analysis if they had missing data such as race and insurance; however, these patients were included in the overall survival analysis.

RESULTS

A total of 427 patients were included for analysis with a median follow-up duration of 25.5 months (range 0.17-179.1 months) after initial evaluation. Fifteen patients had surgery at a median time of 21.0 months (range 11.3-139.3 months) after initial evaluation. The most common indications for surgery were tussive headache in 5 (33.3%), syringomyelia in 5 (33.3%), and nontussive headache in 5 (33.3%). Using the Kaplan-Meier method, rate of freedom from posterior fossa decompression was 95.8%, 94.1%, and 93.1% at 3, 5, and 10 years, respectively.

CONCLUSIONS

Among a large cohort of patients with benign CM-I, progression of imaging abnormalities or symptoms that warrant surgical treatment is infrequent. Therefore, these patients should be managed conservatively. However, clinical follow-up of such individuals is justified, as there is a low, but nonzero, rate of new symptom or syringomyelia development. Future analyses will determine whether imaging or clinical features present at initial evaluation are associated with progression and future need for treatment.

Surgical Treatment in Symptomatic Chiari Malformation Type I: A Series of 25 Adult Patients Treated with Cerebellar Tonsil Shrinkage

BACKGROUND

The variety of symptoms and radiological findings in patients with Chiari malformation type I makes both the indication for surgery and the technical modality controversial. We report our 5-year experience, describing our technique and critically evaluating the clinical results.

METHODS

Between 2012 and 2016, 25 patients (15 female and 10 male; mean age 39.2 years) underwent posterior fossa decompression for Chiari malformation type I. Their clinical complaints included headache, nuchalgia, upper limb weakness or numbness, instability, dizziness and diplopia. Syringomyelia was present in 12 patients (48%). Suboccipital craniectomy was completed in all cases with C1 laminectomy and shrinkage of the cerebellar tonsils by bipolar coagulation; duraplasty was performed with a suturable dura substitute.

RESULTS

Gratifying results were observed in our series. Symptoms and signs were resolved in 52% of patients, and 20% of patients had an improvement in their preoperative deficits. The symptoms of six patients (24%) were essentially unchanged, and one patient (4%) deteriorated despite undergoing surgery. Generally, patients with syringomyelia on magnetic resonance imaging (MRI) showed less symptomatic improvement after surgery. The syrinx disappeared in seven of 12 patients, and complications occurred in three patients (12%).

CONCLUSION

Cerebellar tonsil reduction and restoration of cerebrospinal fluid (CSF) circulation provided clinical improvement and a stable reduction in the syrinx size in the vast majority of treated patients, with a low rate of complications.

The addition of duraplasty to posterior fossa decompression in the surgical treatment of pediatric Chiari malformation Type I: a systematic review and meta-analysis of surgical and performance outcomes

OBJECTIVE Surgery is the definitive treatment of Chiari malformation Type I (CM-I). It involves posterior fossa decompression, which can be performed along with C-1 laminectomy, reconstructive duraplasty, or tonsil shrinkage. The aim of this study was to provide an updated systematic review and meta-analysis of the latest available evidence regarding posterior fossa decompression only (PFDO) versus posterior fossa decompression with duraplasty (PFDD) in the treatment of CM-I in children. METHODS A literature search was performed in compliance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines for article identification, screening, eligibility, and inclusion. Relevant articles were identified from 6 electronic databases from their inception to April 2016. These articles were screened against established criteria for inclusion into this study. RESULTS From 12 relevant studies identified, 1492 pediatric patients treated via PFDD were compared with 1963 pediatric patients treated by PFDO for CM-I. PFDD was associated with greater overall clinical improvement (p = 0.009), along with longer length of stay (p < 0.0001) and more postoperative complications (p = 0.0001) compared with PFDO. No difference was observed between PFDD and PFDO in terms of revision surgery incidence (p = 0.13), estimated blood loss (p = 0.14), syrinx improvement (p = 0.09), or scoliosis improvement (p = 0.95). CONCLUSIONS It appears that the addition of duraplasty to posterior decompression in the definitive treatment of CM-I in children may alter surgical and performance outcomes. In particular, parameters of overall clinical improvement, length of stay, and postoperative complication may differ between children undergoing PFDD and those undergoing PFDO. Current evidence in the literature is of low to very low quality that, as of yet, has not been able to completely control for inherent selection bias both in study design and surgeon preference. Future, large prospective registries and randomized controlled trials are warranted to validate the findings of this study.

Cerebrospinal Fluid and Hydrocephalus: Physiology, Diagnosis, and Treatment

BACKGROUND

Cerebrospinal fluid (CSF) is found around and inside the brain and vertebral column. CSF plays a crucial role in the protection and homeostasis of neural tissue.

METHODS

Key points on the physiology of CSF as well as the diagnostic and treatment options for hydrocephalus are discussed.

RESULTS

Understanding the fundamentals of the production, absorption, dynamics, and pathophysiology of CSF is crucial for addressing hydrocephalus. Shunts and endoscopic third ventriculostomy have changed the therapeutic landscape of hydrocephalus.

CONCLUSIONS

The treatment of hydrocephalus in adults and children represents a large part of everyday practice for the neurologist, both in benign cases and cancer-related diagnoses.

"Stealth cranioplasty:" A novel endeavor for symptomatic adult Chiari I patients with syringomyelia: Technical note, appraisal, and philosophical considerations

Aim and Objective:

In this article, we describe a novel technique of reconstruction of posterior fossa by cranioplasty with use of preshaped titanium mesh following posterior fossa decompression (PFD) for Chiari malformation type I (CMI) with syringomyelia (SM) in symptomatic adults.

Materials and Methods:

Eleven patients underwent limited PFD and expansive cranioplasty with preshaped titanium mesh, what we term as “Stealth Cranioplasty” (SCP), following arachnoid preserving duraplasty (APD) and hexagonal tenting of the duraplasty with the cranioplasty (HTDC) for the management of symptomatic adult CMI with SM. All these patients had syringes extending from 3 to >10 vertebral levels.

Results:

Seven male and four female symptomatic CMI adult patients, between age ranges of 22 and 44 years (mean 29.45 years), presented with different neurological symptoms related to CMI and SM for 6–84 months (mean 37.09 months). All the patients underwent PFD, APD followed by SCP and HTDC and were followed up for 7–54 months (mean 35.90 months). Of 11 patients, 8 patients improved according to the Chicago Chiari Outcome Scale (CCOS) with score of 13–15 while 3 patients remained unchanged with CCOS of 12, and there was no worsening. There was no complication related to Chiari surgery in any of the patients. All the patients had good reestablishment of cisterna magna. Two patients had marked reduction of syrinx while eight patients had moderate-to-mild reduction and one patient had no change of syrinx. None of the patients needed redo surgery.

Conclusion:

SCP is an effective, fruitful, and cost-effective technique for the management of symptomatic adult CMI with SM. This technique has the advantages of preventing complications and recurrences in addition to the improvement of symptoms by addressing the basic pathology.