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Intradural pathology and pathophysiology associated with Chiari I malformation in children and adults with and without syringomyelia.
J Neurosurg Pediatr. 2017 Dec; 20(6):526-541.JN

Abstract

OBJECTIVE

The pathophysiology underlying tonsillar herniation and CSF obstruction in Chiari malformation Type I (CM-I) is unclear, and the cause of CM-I-associated syringomyelia is not well understood. A better understanding of this pathophysiology is important for an improved treatment strategy. Therefore, the authors sought to identify, characterize, and examine the intradural pathology and CSF flow pathophysiology in the posterior fossa and at the level of the foramen magnum that occurs in the setting of CM-I. They determined the incidence of these intradural findings and assessed differences across age, with the degree of tonsillar herniation, and in the presence and absence of syringomyelia.

METHODS

A prospective database initiated in March 2003 recorded all intraoperative findings during surgical treatment of children and adults with CM-I with or without syringomyelia. A total of 389 surgeries for CM-I were performed in 379 patients between March 2003 and June 2016. A total of 109 surgeries were performed in 109 patients with CM-I (without osseoligamentous abnormalities) in whom both a posterior fossa extradural and intradural decompression with duraplasty was performed (first-time intradural procedures). Using a surgical microscope, intradural pathology and obstruction of CSF channels were identified and assessed. Student t-tests and Fisher's exact tests compared groups in a series of univariate analyses, followed by multivariate logistic regression.

RESULTS

The following intradural pathological entities were observed (prevalence noted in parentheses). These include those that did not obstruct CSF flow channels: opacified arachnoid (33.0%), thickened arachnoid (3.7%), ischemic and gliotic tonsils (40.4%), tonsillar cysts (0.9%), and inferior descent of the fourth ventricle and cervicomedullary junction (CMJ) (78.0%). The following intradural pathological entities were observed to obstruct CSF flow channels: medialized tonsils (100%), tonsil overlying and obstructing the foramen of Magendie (21.1%), intertonsillar and tonsil to CMJ arachnoid adhesions (85.3%), vermian posterior inferior cerebellar artery branches obstructing the foramen of Magendie (43.1%), and arachnoid veils or webs obstructing or occluding the foramen of Magendie (52.3%). Arachnoid veils varied in type and were observed in 59.5% of patients with CM-I who had syringomyelia, which was significantly greater than the 33.3% of patients with CM-I without syringomyelia who had an arachnoid veil (p = 0.018). The presence of CM-I with an arachnoid veil had 3.22 times the odds (p = 0.013, 95% CI 1.29-8.07, by multivariate logistic regression) of being associated with syringomyelia, adjusting for tonsillar herniation. The inferior descent of the fourth ventricle and CMJ occurred with a greater degree of tonsillar herniation (p < 0.001) and correlated with a cervicomedullary kink or buckle on preoperative MRI.

CONCLUSIONS

Intradural pathology associated with CM-I with or without syringomyelia exists in many forms, is more prevalent than previously recognized in patients of all ages, and may play a role in the pathophysiology of CM-I tonsillar herniation. Arachnoid veils appear to partially obstruct CSF flow, are significantly more prevalent in cases of CM-I with syringomyelia, and therefore may play a role in the pathophysiology of CM-I-associated syringomyelia.

Authors+Show Affiliations

1Department of Neurosurgery, University of Iowa Hospitals and Clinics, University of Iowa Stead Family Children's Hospital. 2Pappajohn Biomedical Institute, University of Iowa Carver College of Medicine; and.3Department of Biostatistics, College of Public Health, University of Iowa Hospitals and Clinic, Iowa City, Iowa.1Department of Neurosurgery, University of Iowa Hospitals and Clinics, University of Iowa Stead Family Children's Hospital.

Pub Type(s)

Comparative Study
Journal Article

Language

eng

PubMed ID

29027876

Citation

Dlouhy, Brian J., et al. "Intradural Pathology and Pathophysiology Associated With Chiari I Malformation in Children and Adults With and Without Syringomyelia." Journal of Neurosurgery. Pediatrics, vol. 20, no. 6, 2017, pp. 526-541.
Dlouhy BJ, Dawson JD, Menezes AH. Intradural pathology and pathophysiology associated with Chiari I malformation in children and adults with and without syringomyelia. J Neurosurg Pediatr. 2017;20(6):526-541.
Dlouhy, B. J., Dawson, J. D., & Menezes, A. H. (2017). Intradural pathology and pathophysiology associated with Chiari I malformation in children and adults with and without syringomyelia. Journal of Neurosurgery. Pediatrics, 20(6), 526-541. https://doi.org/10.3171/2017.7.PEDS17224
Dlouhy BJ, Dawson JD, Menezes AH. Intradural Pathology and Pathophysiology Associated With Chiari I Malformation in Children and Adults With and Without Syringomyelia. J Neurosurg Pediatr. 2017;20(6):526-541. PubMed PMID: 29027876.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Intradural pathology and pathophysiology associated with Chiari I malformation in children and adults with and without syringomyelia. AU - Dlouhy,Brian J, AU - Dawson,Jeffrey D, AU - Menezes,Arnold H, Y1 - 2017/10/13/ PY - 2017/10/14/pubmed PY - 2017/12/12/medline PY - 2017/10/14/entrez KW - CM-I = Chiari malformation Type I KW - CMJ = cervicomedullary junction KW - Chiari malformation Type I KW - PICA = posterior inferior cerebellar artery KW - arachnoid adhesions KW - arachnoid veil KW - arachnoid web KW - cerebrospinal fluid KW - craniovertebral junction KW - gliotic tonsils KW - ischemic tonsils KW - opaque arachnoid KW - syringomyelia KW - tonsillar herniation SP - 526 EP - 541 JF - Journal of neurosurgery. Pediatrics JO - J Neurosurg Pediatr VL - 20 IS - 6 N2 - OBJECTIVE The pathophysiology underlying tonsillar herniation and CSF obstruction in Chiari malformation Type I (CM-I) is unclear, and the cause of CM-I-associated syringomyelia is not well understood. A better understanding of this pathophysiology is important for an improved treatment strategy. Therefore, the authors sought to identify, characterize, and examine the intradural pathology and CSF flow pathophysiology in the posterior fossa and at the level of the foramen magnum that occurs in the setting of CM-I. They determined the incidence of these intradural findings and assessed differences across age, with the degree of tonsillar herniation, and in the presence and absence of syringomyelia. METHODS A prospective database initiated in March 2003 recorded all intraoperative findings during surgical treatment of children and adults with CM-I with or without syringomyelia. A total of 389 surgeries for CM-I were performed in 379 patients between March 2003 and June 2016. A total of 109 surgeries were performed in 109 patients with CM-I (without osseoligamentous abnormalities) in whom both a posterior fossa extradural and intradural decompression with duraplasty was performed (first-time intradural procedures). Using a surgical microscope, intradural pathology and obstruction of CSF channels were identified and assessed. Student t-tests and Fisher's exact tests compared groups in a series of univariate analyses, followed by multivariate logistic regression. RESULTS The following intradural pathological entities were observed (prevalence noted in parentheses). These include those that did not obstruct CSF flow channels: opacified arachnoid (33.0%), thickened arachnoid (3.7%), ischemic and gliotic tonsils (40.4%), tonsillar cysts (0.9%), and inferior descent of the fourth ventricle and cervicomedullary junction (CMJ) (78.0%). The following intradural pathological entities were observed to obstruct CSF flow channels: medialized tonsils (100%), tonsil overlying and obstructing the foramen of Magendie (21.1%), intertonsillar and tonsil to CMJ arachnoid adhesions (85.3%), vermian posterior inferior cerebellar artery branches obstructing the foramen of Magendie (43.1%), and arachnoid veils or webs obstructing or occluding the foramen of Magendie (52.3%). Arachnoid veils varied in type and were observed in 59.5% of patients with CM-I who had syringomyelia, which was significantly greater than the 33.3% of patients with CM-I without syringomyelia who had an arachnoid veil (p = 0.018). The presence of CM-I with an arachnoid veil had 3.22 times the odds (p = 0.013, 95% CI 1.29-8.07, by multivariate logistic regression) of being associated with syringomyelia, adjusting for tonsillar herniation. The inferior descent of the fourth ventricle and CMJ occurred with a greater degree of tonsillar herniation (p < 0.001) and correlated with a cervicomedullary kink or buckle on preoperative MRI. CONCLUSIONS Intradural pathology associated with CM-I with or without syringomyelia exists in many forms, is more prevalent than previously recognized in patients of all ages, and may play a role in the pathophysiology of CM-I tonsillar herniation. Arachnoid veils appear to partially obstruct CSF flow, are significantly more prevalent in cases of CM-I with syringomyelia, and therefore may play a role in the pathophysiology of CM-I-associated syringomyelia. SN - 1933-0715 UR - https://www.unboundmedicine.com/medline/citation/29027876/Intradural_pathology_and_pathophysiology_associated_with_Chiari_I_malformation_in_children_and_adults_with_and_without_syringomyelia_ L2 - https://thejns.org/doi/10.3171/2017.7.PEDS17224 DB - PRIME DP - Unbound Medicine ER -