Chiari type 1 deformity

Chiari type 1 deformity

Chiari type 1 deformity is a hindbrain disorder associated with elongation of the cerebellar tonsils, which descend below the foramen magnum into the spinal canal.

Defined as cerebellar tonsillar herniation ≥ 5 mm below the foramen magnum 1).

The hindbrain is not malformed but deformed. Accordingly, “Chiari type 1 deformity,” not “Chiari type 1 malformation” is the correct term to characterize primary tonsillar herniation.

Epidemiology

Chiari type 1 deformity is commonly seen in pediatric neurology, neuroradiology, and neurosurgery and may have various clinical presentations depending on patient age. In addition, Chiari type 1 deformity is increasingly found by neuroimaging studies as an incidental finding in asymptomatic children 2).

In the past, it was estimated that the condition occurs in about one in every 1,000 births. However, the increased use of diagnostic imaging has shown that CM may be much more common. Complicating this estimation is the fact that some children who are born with the condition may not show symptoms until adolescence or adulthood, if at all. CMs are more prevalent in certain groups, including people of Celtic descent.

A statistically significant (P = .03) female predominance of the malformation was observed, with a female: male ratio of approximately 3:2.

Associated skeletal anomalies were seen in 24% of patients.

Syringomyelia was detected in 40% of patients, most commonly between the C-4 and C-6 levels. Of the 25 patients who presented with spinal symptoms, 23 (92%) proved to have a syrinx at MR imaging. When the syrinx extended into the medulla (n = 3), however, brainstem symptoms predominated. Patients with objective brain stem or cerebellar syndrome had the largest mean tonsillar herniations. Patients with tonsillar herniations greater than 12 mm were invariably symptomatic, but approximately 30% of patients with tonsils herniating 5-10 mm below the foramen magnum were asymptomatic at MR imaging. “Incidental” Chiari I malformations are thus much more common than previously recognized, and careful clinical assessment remains the cornerstone for proper diagnosis and management 3).

Classification

Etiology

Syndromic craniosynostosis

Chiari malformation Type I (CM-I) related to syndromic craniosynostosis in pediatric patients has been well-studied. The surgical management consists of cranial vault remodeling with or without posterior fossa decompression. There were also cases, in whom CM-I was diagnosed prior to the craniosynostosis in early childhood.

A 16-year-old boy who admitted with symptoms related to CM-I. With careful examination and further genetic investigations, a diagnosis of Crouzon syndrome was made, of which the patient and his family was unaware before. The patient underwent surgery for posterior fossa decompression and followed-up for Crouzon’s syndrome.

This is the only case report indicating a late adolescent diagnosis of Crouzon syndrome through clinical symptoms of an associated CM-I 4).

Familial clustering

A population-based genealogical resource with linked medical data was used to define the observed familial clustering of Chiari malformation Type I (CM-I). METHODS All patients with CM-I were identified from the 2 largest health care providers in Utah; those patients with linked genealogical data were used to test hypotheses regarding familial clustering. Relative risks (RRs) in first-, second-, and third-degree relatives were estimated using internal cohort-specific CM-I rates; the Genealogical Index of Familiality (GIF) test was used to test for an excess of relationships between all patients with CM-I compared with the expected distribution of relationships for matched control sets randomly selected from the resource. Pedigrees with significantly more patients with CM-I than expected (p < 0.05) based on internal rates were identified. RESULTS A total of 2871 patients with CM-I with at least 3 generations of genealogical data were identified. Significantly increased RRs were observed for first- and third-degree relatives (RR 4.54, p < 0.001, and RR 1.36, p < 0.001, respectively); the RR for second-degree relatives was elevated, but not significantly (RR 1.20, p = 0.13). Significant excess pairwise relatedness was observed among the patients with CM-I (p < 0.001), and borderline significant excess pairwise relatedness was observed when all relationships closer than first cousins were ignored (p = 0.051). Multiple extended high-risk CM-I pedigrees with closely and distantly related members were identified. CONCLUSIONS This population-based description of the familial clustering of 2871 patients with CM-I provided strong evidence for a genetic contribution to a predisposition to CM-I 5).

Pathophysiology

The pathophysiology of CMI is poorly understood and it remains unknown how ICP alterations relate to symptoms and radiological findings.

There is some evidence of impaired intracranial compliance as an important pathophysiological mechanism 6).

Magnetic resonance imaging measurement of transcranial CSF flow and blood flow may lead to a better understanding of the pathophysiology of Chiari malformations and may prove to be an important diagnostic tool for guiding for the treatment of patients with Chiari I malformation 7).

The pathogenesis of a Chiari I malformation of the cerebellar tonsils is grouped into 4 general mechanisms. 8).

It appears that the pathogenesis of Chiari malformation with or without associated basilar invagination and/or syringomyelia is primarily related to atlantoaxial instability. The data suggest that the surgical treatment in these cases should be directed toward atlantoaxial stabilization and segmental arthrodesis. Except in cases in which there is assimilation of the atlas, inclusion of the occipital bone is neither indicated nor provides optimum stability. Foramen magnum decompression is not necessary and may be counter-effective in the long run 9). It occurs in children and adults. Clinical symptoms mainly develop from alterations in CSF flow at the foramen magnum and the common subsequent development of syringomyelia.


Patients with Chiari malformation type 1 (CMI) often present with elevated pulsatile and static intracranial pressure (ICP).

Several lines of evidence suggest common pathophysiological mechanisms in Chiari malformation Type I (CMI) and idiopathic intracranial hypertension (IIH). It has been hypothesized that tonsillar ectopy, a typical finding in CMI, is the result of elevated intracranial pressure (ICP) combined with a developmentally small posterior cranial fossa (PCF).

The study of Frič and Eide showed comparable and elevated pulsatile intracranial pressure, indicative of impaired intracranial compliance, in both CMI and IIH cohorts, while static ICP was higher in the IIH cohort. The data did not support the hypothesis that reduced PCFV combined with increased ICP causes tonsillar ectopy in CMI. Even though impaired intracranial compliance seems to be a common pathophysiological mechanism behind both conditions, the mechanisms explaining the different clinical and radiological presentations of CMI and IIH remain undefined 10).

Natural history

Clinical Features

Diagnosis

Along with tonsillar herniation, imaging studies have documented additional abnormalities, including smaller and overcrowded posterior cranial fossa 11) 12) 13) 14) 15).

MRI Findings After Surgery for Chiari Malformation Type I is important when evaluating postoperative changes 16).


Sagittal MRI overestimates the degree of tonsillar ectopia. Misdiagnosis may occur if sagittal imaging alone is used. The cerebellar tonsils are paramedian structures, and this should be kept in mind when interpreting midline sagittal MRI.

Treatment

Outcome

Efforts to guide preoperative counseling and improve outcomes research are impeded by reliance on small, single-center studies.

Approximately 1 in 8 pediatric CM-I patients experienced a surgical complication, whereas medical complications were rare. Although complex chronic conditions (CCC) were common in pediatric CM-I patients, only hydrocephalus was independently associated with increased risk of surgical events. These results may inform patient counseling and guide future research efforts 17).

CM-I in children is not a radiologically static entity but rather is a dynamic one. Radiological changes were seen throughout the 7 years of follow-up. A reduction in tonsillar herniation was substantially more common than an increase. Radiological changes did not correlate with neurological examination finding changes, symptom development, or the need for future surgery. Follow-up imaging of asymptomatic children with CM-I did not alter treatment for any patient. It would be reasonable to follow these children with clinical examinations but without regular surveillance MRI 18).

Outcome assessment for the management of Chiari malformation type 1 is difficult because of the lack of a reliable and specific surgical outcome assessment scale. Such a scale could reliably correlate postoperative outcomes with preoperative symptoms.

Outcome is poor in approximately 3 in 10 patients 19).

The degree of tonsillar herniation has not been a reliable predictor of either symptom severity 20) or surgical outcome 21).

Arnautovic et al. identified 145 operative series of patients with CM-I, primarily from the United States and Europe, and divided patient ages into 1 of 3 categories: adult (> 18 years of age; 27% of the cases), pediatric (≤ 18 years of age; 30%), or unknown (43%). Most series (76%) were published in the previous 21 years. The median number of patients in the series was 31. The mean duration of the studies was 10 years, and the mean follow-up time was 43 months. The peak ages of presentation in the pediatric studies were 8 years, followed by 9 years, and in the adult series, 41 years, followed by 46 years. The incidence of syringomyelia was 65%. Most of the studies (99%) reported the use of posterior fossa/foramen magnum decompression. In 92%, the dura was opened, and in 65% of these cases, the arachnoid was opened and dissected; tonsillar resection was performed in 27% of these patients. Postoperatively, syringomyelia improved or resolved in 78% of the patients. Most series (80%) reported postoperative neurological outcomes as follows: 75% improved, 17% showed no change, and 9% experienced worsening. Postoperative headaches improved or resolved in 81% of the patients, with a statistical difference in favor of the pediatric series. Postoperative complications were reported for 41% of the series, most commonly with CSF leak, pseudomeningocele, aseptic meningitis, wound infection, meningitis, and neurological deficit, with a mean complication rate of 4.5%. Complications were reported for 37% of pediatric, 20% of adult, and 43% of combined series. Mortality was reported for 11% of the series. No difference in mortality rates was seen between the pediatric and adult series 22).

Scales

Sports

There is currently no consensus on the safety of sports participation for patients with Chiari I malformation (CM-I).

A prospective survey was administered to 503 CM-I patients at 2 sites over a 46-month period. Data were gathered on imaging characteristics, treatment, sports participation, and any sport-related injuries. Additionally, 81 patients completed at least 1 subsequent survey following their initial entry into the registry and were included in a prospective group, with a mean prospective follow-up period of 11 months.

Of the 503 CM-I patients, 328 participated in sports for a cumulative duration of 4641 seasons; 205 of these patients participated in contact sports. There were no serious or catastrophic neurological injuries. One patient had temporary extremity paresthesias that resolved within hours, and this was not definitely considered to be related to the CM-I. In the prospective cohort, there were no permanent neurological injuries.

No permanent or catastrophic neurological injuries were observed in CM-I patients participating in athletic activities. The authors believe that the risk of such injuries is low and that, in most cases, sports participation by children with CM-I is safe 23).

Systematic reviews and meta-analysis

Case series

Case reports

Books

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References

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Poretti A, Ashmawy R, Garzon-Muvdi T, Jallo GI, Huisman TA, Raybaud C. Chiari Type 1 Deformity in Children: Pathogenetic, Clinical, Neuroimaging, and Management Aspects. Neuropediatrics. 2016 Jun 23. [Epub ahead of print] PubMed PMID: 27337547.
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Canpolat A, Akçakaya MO, Altunrende E, Ozlü HM, Duman H, Ton T, Akdemir O. Chiari Type I malformation yielded to the diagnosis of Crouzon syndrome. J Neurosci Rural Pract. 2014 Jan;5(1):81-3. doi: 10.4103/0976-3147.127885. PubMed PMID: 24741262.
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Abbott D, Brockmeyer D, Neklason DW, Teerlink C, Cannon-Albright LA. Population-based description of familial clustering of Chiari malformation Type I. J Neurosurg. 2017 Feb 3:1-6. doi: 10.3171/2016.9.JNS161274. [Epub ahead of print] PubMed PMID: 28156254.
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Frič R, Eide PK. Comparison of pulsatile and static pressures within the intracranial and lumbar compartments in patients with Chiari malformation type 1: a prospective observational study. Acta Neurochir (Wien). 2015 Sep;157(8):1411-23; discussion 1423. doi: 10.1007/s00701-015-2465-x. Epub 2015 Jun 24. PubMed PMID: 26105759.
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Alperin N, Kulkarni K, Loth F, Roitberg B, Foroohar M, Mafee MF, Lichtor T. Analysis of magnetic resonance imaging-based blood and cerebrospinal fluid flow measurements in patients with Chiari I malformation: a system approach. Neurosurg Focus. 2001 Jul 15;11(1):E6. PubMed PMID: 16724816.
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Buell TJ, Heiss JD, Oldfield EH. Pathogenesis and Cerebrospinal Fluid Hydrodynamics of the Chiari I Malformation. Neurosurg Clin N Am. 2015 Oct;26(4):495-9. doi: 10.1016/j.nec.2015.06.003. Epub 2015 Aug 4. Review. PubMed PMID: 26408057.
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Goel A. Is atlantoaxial instability the cause of Chiari malformation? Outcome analysis of 65 patients treated by atlantoaxial fixation. J Neurosurg Spine. 2015 Feb;22(2):116-27. doi: 10.3171/2014.10.SPINE14176. Epub 2014 Nov 21. PubMed PMID: 25415487.
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Frič R, Eide PK. Comparative observational study on the clinical presentation, intracranial volume measurements, and intracranial pressure scores in patients with either Chiari malformation Type I or idiopathic intracranial hypertension. J Neurosurg. 2016 Jun 24:1-11. [Epub ahead of print] PubMed PMID: 27341045.
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Nishikawa M, Sakamoto H, Hakuba A, Nakanishi N, Inoue Y. Pathogenesis of Chiari malformation: a morphometric study of the posterior cranial fossa. J Neurosurg. 1997;86(1):40-47.
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Milhorat TH, Chou MW, Trinidad EM, et al. Chiari I malformation redefined: clinical and radiographic findings for 364 symptomatic patients. Neurosurgery. 1999;44(5):1005-1017.
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Karagöz F, Izgi N, Kapíjcíjo!glu Sencer S. Morphometric measurements of the cranium in patients with Chiari type I malformation and comparison with the normal population. Acta Neurochir (Wien). 2002;144(2):165-171; discussion 171.
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Milhorat TH, Nishikawa M, Kula RW, Dlugacz YD. Mechanisms of cerebellar tonsil herniation in patients with Chiari malformations as guide to clinical management. Acta Neurochir (Wien). 2010;152(7):1117-1127.
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Badie B, Mendoza D, Batzdorf U. Posterior fossa volume and response to suboccipital decompression in patients with Chiari I malformation. Neurosurgery. 1995;37(2):214-218.
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Rozenfeld M, Frim DM, Katzman GL, Ginat DT. MRI Findings After Surgery for Chiari Malformation Type I. AJR Am J Roentgenol. 2015 Nov;205(5):1086-93. doi: 10.2214/AJR.15.14314. PubMed PMID: 26496557.
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Greenberg JK, Olsen MA, Yarbrough CK, Ladner TR, Shannon CN, Piccirillo JF, Anderson RC, Wellons JC 3rd, Smyth MD, Park TS, Limbrick DD Jr. Chiari malformation Type I surgery in pediatric patients. Part 2: complications and the influence of comorbid disease in California, Florida, and New York. J Neurosurg Pediatr. 2016 May;17(5):525-32. doi: 10.3171/2015.10.PEDS15369. Epub 2016 Jan 22. PubMed PMID: 26799408.
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Whitson WJ, Lane JR, Bauer DF, Durham SR. A prospective natural history study of nonoperatively managed Chiari I malformation: does follow-up MRI surveillance alter surgical decision making? J Neurosurg Pediatr. 2015 Aug;16(2):159-66. doi: 10.3171/2014.12.PEDS14301. Epub 2015 May 1. PubMed PMID: 25932776.
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Aliaga L, Hekman KE, Yassari R, Straus D, Luther G, Chen J, Sampat A, Frim D. A novel scoring system for assessing Chiari malformation type I treatment outcomes. Neurosurgery. 2012 Mar;70(3):656-64; discussion 664-5. doi: 10.1227/NEU.0b013e31823200a6. PubMed PMID: 21849925.
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Khan AA, Bhatti SN, Khan G, et al. Clinical and radiological findings in Arnold Chiari malformation. J Ayub Med Coll Abbottabad. 2010;22(2):75-78.
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NoudelR,GomisP,SotoaresG,etal.Posteriorfossavolumeincreaseaftersurgery for Chiari malformation type I: a quantitative assessment using magnetic resonance imaging and correlations with the treatment response. J Neurosurg. 2011;115(3): 647-658.
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Arnautovic A, Splavski B, Boop FA, Arnautovic KI. Pediatric and adult Chiari malformation Type I surgical series 1965-2013: a review of demographics, operative treatment, and outcomes. J Neurosurg Pediatr. 2015 Feb;15(2):161-77. doi: 10.3171/2014.10.PEDS14295. Epub 2014 Dec 5. PubMed PMID: 25479580.
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Strahle J, Geh N, Selzer BJ, Bower R, Himedan M, Strahle M, Wetjen NM, Muraszko KM, Garton HJ, Maher CO. Sports participation with Chiari I malformation. J Neurosurg Pediatr. 2016 Apr;17(4):403-9. doi: 10.3171/2015.8.PEDS15188. Epub 2015 Dec 4. PubMed PMID: 26636249.

Chiari related scoliosis

Chiari related scoliosis

Spinal deformity is an important clinical manifestation of Chiari type 1 deformity and syringomyelia.

Epidemiology

The prevalence of scoliosis in patients with Chiari Malformation and syringomyelia(CIM+SM) approaches 80% in some studies1) 2) 3) 4) 5).

Risk factors

Previous authors have suggested that risk factors for curve progression and spinal fusion include older age, the location of spinal deformity, extent of syrinx resolution, and degree of initial scoliosis 6) 7) 8) 9) 10) 11).

Syrinx characteristics, but not tonsil position, were related to the presence of scoliosis in patients with CM-I, and there was an independent association of syrinx length and holocord syrinx with scoliosis. Further study is needed to evaluate the nature of the relationship between syrinx and scoliosis in patients with CM-I 12).

Diagnosis

A challenge for physicians who see children with scoliosis is deciding when an MRI is warranted to look for neurological problems such as Chiari. Since scoliosis is not uncommon among adolescents, and because only a small percentage of those cases are actually related to Chiari, ordering an MRI for every child with scoliosis is not practical. In several studies, researchers have tried to find unique characteristics of Chiari related scoliosis which can alert doctors to when an MRI should be performed. Based on this work, some doctors recommend that Chiari should be checked for if there are any neurological signs and/or severe curves. Others have tried to focus on curve patterns that aren’t typically seen, for example certain types of double curves.

Outcome

The safety posterior spinal fusion and deformity correction in CIM+SM remains controversial and the outcomes are not well described 13) 14) 15) 16)17) 18).

Up to half of patients require spinal fusion despite neurosurgical intervention and nonoperative management 19) 20) 21) 22) 23).

While CIM+SM patients undergoing spine reconstruction can expect similar deformity corrections and outcomes scores to AIS patients, they also experience higher rates of neuromonitoring difficulties and neurological complications related to surgery. Surgeons should be prepared for these difficulties, particularly in children with larger syrinx size 24).

Case series

A large multicenter retrospective and prospective registry of pediatric patients with CM-I (tonsils ≥ 5 mm below the foramen magnum) and syrinx (≥ 3 mm in axial width) was reviewed for clinical and radiological characteristics of CM-I, syrinx, and scoliosis (coronal curve ≥ 10°).

Based on available imaging of patients with CM-I and syrinx, 260 of 825 patients (31%) had a clear diagnosis of scoliosis based on radiographs or coronal MRI. Forty-nine patients (5.9%) did not have scoliosis, and in 516 (63%) patients, a clear determination of the presence or absence of scoliosis could not be made. Comparison of patients with and those without a definite scoliosis diagnosis indicated that scoliosis was associated with wider syrinxes (8.7 vs 6.3 mm, OR 1.25, p < 0.001), longer syrinxes (10.3 vs 6.2 levels, OR 1.18, p < 0.001), syrinxes with their rostral extent located in the cervical spine (94% vs 80%, OR 3.91, p = 0.001), and holocord syrinxes (50% vs 16%, OR 5.61, p < 0.001). Multivariable regression analysis revealed syrinx length and the presence of holocord syrinx to be independent predictors of scoliosis in this patient cohort. Scoliosis was not associated with sex, age at CM-I diagnosis, tonsil position, pB-C2 distance (measured perpendicular distance from the ventral dura to a line drawn from the basion to the posterior-inferior aspect of C2), clivoaxial angle, or frontal-occipital horn ratio. Average curve magnitude was 29.9°, and 37.7% of patients had a left thoracic curve. Older age at CM-I or syrinx diagnosis (p < 0.0001) was associated with greater curve magnitude whereas there was no association between syrinx dimensions and curve magnitude.

Syrinx characteristics, but not tonsil position, were related to the presence of scoliosis in patients with CM-I, and there was an independent association of syrinx length and holocord syrinx with scoliosis. Further study is needed to evaluate the nature of the relationship between syrinx and scoliosis in patients with CM-I 25).

2018

Chotai et al. conducted a retrospective review at a single tertiary center for children undergoing Posterior fossa decompression (PFD) with untreated scoliosis, and identified 17 patients with complete follow-up data and imaging.

Overall, scoliosis improved in 7 (41.2%) patients, worsened in 9 (52.9%), and remained unchanged in 1 (5.9%) after PFD (mean follow-up of 7.8 ± 4.1 months). We found that 3 of the 8 (38%) children with early-onset scoliosis eventually needed scoliosis corrective surgery, which was needed in 7 of the 9 (78%) patients with adolescent-onset scoliosis. In addition, only 1 patient (17%) with a preoperative scoliosis curve <35 degrees and 9 patients (82%) with a curve ≥35 degrees required surgery for scoliosis correction despite PFD (p = 0.018).

In certain patients, PFD for CM-I may lead to improvement or stabilization of scoliosis 26).

2017

Previous reports have addressed the short-term response of patients with Chiari-related scoliosis (CRS) to suboccipital decompression and duraplasty (SODD); however, the long-term behavior of the curve has not been well defined.

Ravindra et al. undertook a longitudinal study of a cohort of patients who underwent SODD for CRS to determine whether there are factors related to Chiari malformation (CM) that predict long-term scoliotic curve behavior and need for deformity correction. METHODS The authors retrospectively reviewed cases in which patients underwent SODD for CRS during a 14-year period at a single center. Clinical (age, sex, and associated disorders/syndromes) and radiographic (CM type, tonsillar descent, pBC2 line, clival-axial angle [CXA], syrinx length and level, and initial Cobb angle) information was evaluated to identify associations with the primary outcome: delayed thoracolumbar fusion for progressive scoliosis. RESULTS Twenty-eight patients were identified, but 4 were lost to follow-up and 1 underwent fusion within a year. Among the remaining 23 patients, 11 required fusion surgery at an average of 88.3 ± 15.4 months after SODD, including 7 (30%) who needed fusion more than 5 years after SODD. On univariate analysis, a lower CXA (131.5° ± 4.8° vs 146.5° ± 4.6°, p = 0.034), pBC2 > 9 mm (64% vs 25%, p = 0.06), and higher initial Cobb angle (35.1° ± 3.6° vs 22.8° ± 4.0°, p = 0.035) were associated with the need for thoracolumbar fusion. Multivariable modeling revealed that lower CXA was independently associated with a need for delayed thoracolumbar fusion (OR 1.12, p = 0.0128).

This investigation demonstrates the long-term outcome and natural history of CRS after SODD. The durability of the effect of SODD on CRS and curve behavior is poor, with late curve progression occurring in 30% of patients. Factors associated with CRS progression include an initial pBC2 > 9 mm, lower CXA, and higher Cobb angle. Lower CXA was an independent predictor of delayed thoracolumbar fusion. Further study is necessary on a larger cohort of patients to fully elucidate this relationship 27).

2016

Mackel et al. conducted a multicenter retrospective review of 44 patients, aged 18 years or younger, diagnosed with Chiari I malformation and scoliosis who underwent posterior fossa decompression from 2000 to 2010. The outcome of interest was the need for spinal fusion after decompression. RESULTS Overall, 18 patients (40%) underwent posterior fossa decompression alone, and 26 patients (60%) required a spinal fusion after the decompression. The mean Cobb angle at presentation and the proportion of patients with curves > 35° differed between the decompression-only and fusion cohorts (30.7° ± 11.8° vs 52.1° ± 26.3°, p = 0.002; 5 of 18 vs 17 of 26, p = 0.031). An odds ratio of 1.0625 favoring a need for fusion was established for each 1° of increase in Cobb angle (p = 0.012, OR 1.0625, 95% CI 1.0135-1.1138). Among the 14 patients older than 10 years of age with a primary Cobb angle exceeding 35°, 13 (93%) ultimately required fusion. Patients with at least 1 year of follow-up whose curves progressed more 10° after decompression were younger than those without curve progression (6.1 ± 3.0 years vs 13.7 ± 3.2 years, p = 0.001, Mann-Whitney U-test). Left apical thoracic curves constituted a higher proportion of curves in the decompression-only group (8 of 16 vs 1 of 21, p = 0.002). CONCLUSIONS The need for fusion after posterior fossa decompression reflected the curve severity at clinical presentation. Patients presenting with curves measuring > 35°, as well as those greater than 10 years of age, may be at greater risk for requiring fusion after posterior fossa decompression, while patients less than 10 years of age may require routine monitoring for curve progression. Left apical thoracic curves may have a better response to Chiari malformation decompression 28).

2015

Strahle et al. sought to determine if there is an independent association between CM-I and scoliosis when controlling for syrinx status.

The medical records of 14,118 consecutive patients aged ≤ 18 years who underwent brain or cervical spine MRI at a single institution in an 11-year span were reviewed to identify patients with CM-I, scoliosis, and/or syrinx. The relationship between CM-I and scoliosis was analyzed by using multivariate regression analysis and controlling for age, sex, CM-I status, and syrinx status.

In this cohort, 509 patients had CM-I, 1740 patients had scoliosis, and 243 patients had a spinal syrinx. The presence of CM-I, the presence of syrinx, older age, and female sex were each significantly associated with scoliosis in the univariate analysis. In the multivariate regression analysis, older age (OR 1.02 [95% CI 1.01-1.03]; p < 0.0001), female sex (OR 1.71 [95% CI 1.54-1.90]; p < 0.0001), and syrinx (OR 9.08 [95% CI 6.82-12.10]; p < 0.0001) were each independently associated with scoliosis. CM-I was not independently associated with scoliosis when controlling for these other variables (OR 0.99 [95% CI 0.79-1.29]; p = 0.9).

A syrinx was independently associated with scoliosis in a large pediatric population undergoing MRI. CM-I was not independently associated with scoliosis when controlling for age, sex, and syrinx status. Because CM-I is not independently associated with scoliosis, scoliosis should not necessarily be considered a symptom of low cerebellar tonsil position in patients without a syrinx 29).

2013

A retrospective study was conducted on 22 patients with CMS who received brace treatment of scoliosis after PFD. Forty-four age- and sex-matched patients with idiopathic scoliosis (IS) who were treated with bracing served as the control group. The bracing outcome was considered a failure if the curve worsened 6° or more; otherwise, the treatment was considered to be successful.

The age and Risser sign were similar between patients with CMS and IS at brace initiation. The initial curve magnitude of patients with CMS(mean, 32.9° ± 6.3°; range, 20°-45°) was marginally significantly larger than that of patients with IS (mean, 29.6° ± 6.4°; range, 20°-45°). Until the final follow-up, a 6° or more worsening of the major curve occurred in 8 patients with CMS (36%) and in 15 patients with IS (34%). Overall, 7 patients with CMS (32%) and 13 patients with IS (30%) underwent spinal fusion surgery. No significant differences were observed between the 2 groups in the surgery rates or the bracing success rates (P > 0.05). In patients with CMS, neither the performance of syringosubarachnoid shunting nor the extent of tonsillar descent correlated with the bracing outcomes, whereas a double major curve pattern was found to be predictive for the failure of bracing.

Brace treatment subsequent to PFD is effective in preventing curve progression for 64% of patients with CMS, which is comparable with the rate that is observed in patients with IS. Double major curve pattern may be a risk factor in predicting treatment failure in patients with CMS 30).

Case reports

Tanaka et al. report the result of an 8-year follow-up of a 13-year-old girl with severe scoliosis associated with Chiari malformation and a large syringomyelia. The patient presented at the hospital at the age of 13 with a 68° scoliosis. Magnetic resonance imaging showed Chiari malformation and a large syringomyelia. Neurosurgical treatment involved foramen magnum decompression and partial C1 laminectomy, but the scoliosis still progressed.

They present the first case report of a rare course of scoliosis in a patient with CM-I and a large syringomyelia 31).

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Attenello FJ, McGirt MJ, Garcés-Ambrossi GL, Chaichana KL, Carson B, Jallo GI. Suboccipital decompression for Chiari I malformation: outcome comparison of duraplasty with expanded polytetrafluoroethylene dural substitute versus pericranial autograft. Childs Nerv Syst. 2009;25:183–90.
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Bhangoo R, Sgouros S. Scoliosis in children with Chiari I-related syringomyelia. Childs Nerv Syst. 2006;22:1154–7.
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Hwang SW, Samdani AF, Jea A, et al. Outcomes of Chiari I-associated scoliosis after intervention: a meta-analysis of the pediatric literature. Childs Nerv Syst. 2012
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Ozerdemoglu Ra, Transfeldt EE, Denis F. Value of treating primary causes of syrinx in scoliosis associated with syringomyelia. Spine. 2003;28:806–14.
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Sengupta DK, Dorgan J, Findlay GF. Can hindbrain decompression for syringomyelia lead to regression of scoliosis? Eur Spine J. 2000;9:198–201.
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Strahle JM, Taiwo R, Averill C, Torner J, Shannon CN, Bonfield CM, Tuite GF, Bethel-Anderson T, Rutlin J, Brockmeyer DL, Wellons JC, Leonard JR, Mangano FT, Johnston JM, Shah MN, Iskandar BJ, Tyler-Kabara EC, Daniels DJ, Jackson EM, Grant GA, Couture DE, Adelson PD, Alden TD, Aldana PR, Anderson RCE, Selden NR, Baird LC, Bierbrauer K, Chern JJ, Whitehead WE, Ellenbogen RG, Fuchs HE, Guillaume DJ, Hankinson TC, Iantosca MR, Oakes WJ, Keating RF, Khan NR, Muhlbauer MS, McComb JG, Menezes AH, Ragheb J, Smith JL, Maher CO, Greene S, Kelly M, O’Neill BR, Krieger MD, Tamber M, Durham SR, Olavarria G, Stone SSD, Kaufman BA, Heuer GG, Bauer DF, Albert G, Greenfield JP, Wait SD, Van Poppel MD, Eskandari R, Mapstone T, Shimony JS, Dacey RG, Smyth MD, Park TS, Limbrick DD. Radiological and clinical predictors of scoliosis in patients with Chiari malformation type I and spinal cord syrinx from the Park-Reeves Syringomyelia Research Consortium. J Neurosurg Pediatr. 2019 Aug 16:1-8. doi: 10.3171/2019.5.PEDS18527. [Epub ahead of print] PubMed PMID: 31419800.
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Bradley LJ, Ratahi ED, Crawford Ha, Barnes MJ. The outcomes of scoliosis surgery in patients with syringomyelia. Spine. 2007;32:2327–33.
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Godzik J, Holekamp TF, Limbrick DD, Lenke LG, Park TS, Ray WZ, Bridwell KH, Kelly MP. Risks and outcomes of spinal deformity surgery in Chiari malformation, Type 1, with syringomyelia versus adolescent idiopathic scoliosis. Spine J. 2015 Sep 1;15(9):2002-8. doi: 10.1016/j.spinee.2015.04.048. Epub 2015 May 7. PubMed PMID: 25959792; PubMed Central PMCID: PMC4550545.
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Posterior fossa decompression for Chiari type 1 deformity

Posterior fossa decompression for Chiari type 1 deformity

Despite decades of experience and research, the etiology and management of Chiari type 1 deformity (CM-I) continue to raise more questions than answers. Controversy abounds in every aspect of management, including the indications, timing, and type of surgery, as well as clinical and radiographic outcomes.

A review of recent literature on the management of CM-I in pediatric patients was presented by Alexander et al., along with the experience in managing 1073 patients who were diagnosed with CM-I over the past two decades (1998-2018) at Children’s National Medical Center.

The general trend reveals an increase in the diagnosis of CM-I at younger ages with a significant proportion of these being incidental findings (0.5-3.6%) in asymptomatic patients as well as a rise in the number of patients undergoing Chiari posterior fossa decompression surgery (PFD). The type of surgical intervention varies widely. At there institution, 104 (37%) Chiari surgeries were bone-only PFD with/without outer leaf durectomy, whereas 177 (63%) were PFD with duraplasty. They did not find a significant difference in outcomes between the PFD and PFDD groups (p = 0.59). An analysis of failures revealed a significant difference between patients who underwent tonsillar coagulation versus those whose tonsils were not manipulated (p = 0.02).

While the optimal surgical intervention continues to remain elusive, there is a shift away from intradural techniques in favor of a simple, extradural approach (including dural delamination) in pediatric patients due to high rates of clinical and radiographic success, along with a lower complication rate. The efficacy, safety, and necessity of tonsillar manipulation continue to be heavily contested, as evidence increasingly supports the efficacy and safety of less tonsillar manipulation, including there own experience 1).


An accurate and reliable selection of patients based on clinical and neuroimaging findings is paramount for the success of neurosurgical treatment2).


The preferred treatment for Chiari type 1 deformity is foramen magnum decompression (FMD), and it is assumed to normalise ICP and craniospinal pressure dissociation.

Observations suggest that anatomical restoration of cerebrospinal fluid pathways by FMD does not lead to immediate normalisation of preoperatively altered pulsatile and static ICP in patients with CMI. This finding may explain persistent symptoms during the early period after FMD3).


A variety of surgical techniques for CM-I have been used, and there is a controversy whether to use posterior fossa decompression with duraplasty(PFDD) or posterior fossa decompression without duraplasty (PFD) in CM-I patients.

Chen et al., compared the clinical results and effectiveness of PFDD and PFD in adult patients with CM-I. The cases of 103 adult CM-I patients who underwent posterior fossa decompression with or without duraplasty from 2008 to 2014 were reviewed retrospectively. Patients were divided into 2 groups according to the surgical techniques: PFDD group (n = 70) and PFD group (n = 33). We compared the demographics, preoperative symptoms, radiographic characteristics, postoperative complications, and clinical outcomes between the PFD and PFDD patients. No statistically significant differences were found between the PFDD and PFD groups with regard to demographics, preoperative symptoms, radiographic characteristics, and clinical outcomes(P > 0.05); however, the postoperative complication aseptic meningitis occurred more frequently in the PFDD group than in the PFD group (P = 0.027). We also performed a literature review about the PFDD and PFD and made a summary of these preview studies. Our study suggests that both PFDD and PFD could achieve similar clinical outcomes for adult CM-I patients. The choice of surgical procedure should be based on the patient’s condition. PFDD may lead to a higher complication rate and autologous grafts seemed to perform better than nonautologous grafts for duraplasty 4).


The purpose of a study was to examine the utility of iMRI in determining when an adequate decompression had been performed.

Patients with symptomatic Chiari I malformations with imaging findings of obstruction of the CSF space at the foramen magnum, with or without syringomyelia, were considered candidates for surgery. All patients underwent complete T1, T2, and cine MRI studies in the supine position preoperatively as a baseline. After the patient was placed prone with the neck flexed in position for surgery, iMRI was performed. The patient then underwent a bone decompression of the foramen magnum and arch of C-1, and the MRI was repeated. If obstruction was still present, then in a stepwise fashion the patient underwent dural splitting, duraplasty, and coagulation of the tonsils, with an iMRI study performed after each step guiding the decision to proceed further.

Eighteen patients underwent PFD for Chiari I malformations between November 2011 and February 2013; 15 prone preincision iMRIs were performed. Fourteen of these patients (93%) demonstrated significant improvement of CSF flow through the foramen magnum dorsal to the tonsils with positioning only. This improvement was so notable that changes in CSF flow as a result of the bone decompression were difficult to discern.

The authors observed significant CSF flow changes when simply positioning the patient for surgery. These results put into question intraoperative flow assessments that suggest adequate decompression by PFD, whether by iMRI or intraoperative ultrasound. The use of intraoperative imaging during PFD for Chiari I malformation, whether by ultrasound or iMRI, is limited by CSF flow dynamics across the foramen magnum that change significantly when the patient is positioned for surgery 5).

Complications

References

1)

Alexander H, Tsering D, Myseros JS, Magge SN, Oluigbo C, Sanchez CE, Keating RF. Management of Chiari I malformations: a paradigm in evolution. Childs Nerv Syst. 2019 Jul 27. doi: 10.1007/s00381-019-04265-2. [Epub ahead of print] PubMed PMID: 31352576.
2)

Poretti A, Ashmawy R, Garzon-Muvdi T, Jallo GI, Huisman TA, Raybaud C. Chiari Type 1 Deformity in Children: Pathogenetic, Clinical, Neuroimaging, and Management Aspects. Neuropediatrics. 2016 Jun 23. [Epub ahead of print] PubMed PMID: 27337547.
3)

Frič R, Eide PK. Perioperative monitoring of pulsatile and static intracranial pressure in patients with Chiari malformation type 1 undergoing foramen magnum decompression. Acta Neurochir (Wien). 2016 Feb;158(2):341-7. doi: 10.1007/s00701-015-2669-0. Epub 2015 Dec 28. PubMed PMID: 26711284.
4)

Chen J, Li Y, Wang T, Gao J, Xu J, Lai R, Tan D. Comparison of posterior fossa decompression with and without duraplasty for the surgical treatment of Chiari malformation type I in adult patients: A retrospective analysis of 103 patients. Medicine (Baltimore). 2017 Jan;96(4):e5945. doi: 10.1097/MD.0000000000005945. PubMed PMID: 28121938.
5)

Bond AE, Jane JA Sr, Liu KC, Oldfield EH. Changes in cerebrospinal fluid flow assessed using intraoperative MRI during posterior fossa decompression for Chiari malformation. J Neurosurg. 2015 May;122(5):1068-75. doi: 10.3171/2015.1.JNS132712. Epub 2015 Feb 20. PubMed PMID: 25699415.
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