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Posterior odontoid process angulation in pediatric Chiari I malformation: an MRI morphometric external validation study.
J Neurosurg Pediatr. 2015 Aug; 16(2):138-45.JN

Abstract

OBJECT Osseous anomalies of the craniocervical junction are hypothesized to precipitate the hindbrain herniation observed in Chiari I malformation (CM-I). Previous work by Tubbs et al. showed that posterior angulation of the odontoid process is more prevalent in children with CM-I than in healthy controls. The present study is an external validation of that report. The goals of our study were 3-fold: 1) to externally validate the results of Tubbs et al. in a different patient population; 2) to compare how morphometric parameters vary with age, sex, and symptomatology; and 3) to develop a correlative model for tonsillar ectopia in CM-I based on these measurements.

METHODS

The authors performed a retrospective review of 119 patients who underwent posterior fossa decompression with duraplasty at the Monroe Carell Jr. Children's Hospital at Vanderbilt University; 78 of these patients had imaging available for review. Demographic and clinical variables were collected. A neuroradiologist retrospectively evaluated preoperative MRI examinations in these 78 patients and recorded the following measurements: McRae line length; obex displacement length; odontoid process parameters (height, angle of retroflexion, and angle of retroversion); perpendicular distance to the basion-C2 line (pB-C2 line); length of cerebellar tonsillar ectopia; caudal extent of the cerebellar tonsils; and presence, location, and size of syringomyelia. Odontoid retroflexion grade was classified as Grade 0, > 90°; Grade I,85°-89°; Grade II, 80°-84°; and Grade III, < 80°. Age groups were defined as 0-6 years, 7-12 years, and 13-17 years at the time of surgery. Univariate and multivariate linear regression analyses, Kruskal-Wallis 1-way ANOVA, and Fisher's exact test were performed to assess the relationship between age, sex, and symptomatology with these craniometric variables.

RESULTS

The prevalence of posterior odontoid angulation was 81%, which is almost identical to that in the previous report (84%). With increasing age, the odontoid height (p < 0.001) and pB-C2 length (p < 0.001) increased, while the odontoid process became more posteriorly inclined (p = 0.010). The pB-C2 line was significantly longer in girls (p = 0.006). These measurements did not significantly correlate with symptomatology. Length of tonsillar ectopia in pediatric CM-I correlated with an enlarged foramen magnum (p = 0.023), increasing obex displacement (p = 0.020), and increasing odontoid retroflexion (p < 0.001).

CONCLUSIONS

Anomalous bony development of the craniocervical junction is a consistent feature of CM-I in children. The authors found that the population at their center was characterized by posterior angulation of the odontoid process in 81% of cases, similar to findings by Tubbs et al. (84%). The odontoid process appeared to lengthen and become more posteriorly inclined with age. Increased tonsillar ectopia was associated with more posterior odontoid angulation, a widened foramen magnum, and an inferiorly displaced obex.

Authors+Show Affiliations

Department of 1 Neurological Surgery and.Department of 1 Neurological Surgery and.Radiology, Vanderbilt University School of Medicine, Nashville, Tennessee; and.Department of 1 Neurological Surgery and.Department of Neurological Surgery, Dell Children's Medical Center of Central Texas, Austin, Texas.Department of 1 Neurological Surgery and.Department of 1 Neurological Surgery and.

Pub Type(s)

Journal Article
Validation Study

Language

eng

PubMed ID

26053869

Citation

Ladner, Travis R., et al. "Posterior Odontoid Process Angulation in Pediatric Chiari I Malformation: an MRI Morphometric External Validation Study." Journal of Neurosurgery. Pediatrics, vol. 16, no. 2, 2015, pp. 138-45.
Ladner TR, Dewan MC, Day MA, et al. Posterior odontoid process angulation in pediatric Chiari I malformation: an MRI morphometric external validation study. J Neurosurg Pediatr. 2015;16(2):138-45.
Ladner, T. R., Dewan, M. C., Day, M. A., Shannon, C. N., Tomycz, L., Tulipan, N., & Wellons, J. C. (2015). Posterior odontoid process angulation in pediatric Chiari I malformation: an MRI morphometric external validation study. Journal of Neurosurgery. Pediatrics, 16(2), 138-45. https://doi.org/10.3171/2015.1.PEDS14475
Ladner TR, et al. Posterior Odontoid Process Angulation in Pediatric Chiari I Malformation: an MRI Morphometric External Validation Study. J Neurosurg Pediatr. 2015;16(2):138-45. PubMed PMID: 26053869.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Posterior odontoid process angulation in pediatric Chiari I malformation: an MRI morphometric external validation study. AU - Ladner,Travis R, AU - Dewan,Michael C, AU - Day,Matthew A, AU - Shannon,Chevis N, AU - Tomycz,Luke, AU - Tulipan,Noel, AU - Wellons,John C,3rd Y1 - 2015/05/22/ PY - 2015/6/9/entrez PY - 2015/6/9/pubmed PY - 2015/10/23/medline KW - CCJ = craniocervical junction KW - CM-I = Chiari I malformation KW - Chiari I malformation KW - craniocervical junction KW - dens KW - morphometry KW - syringomyelia SP - 138 EP - 45 JF - Journal of neurosurgery. Pediatrics JO - J Neurosurg Pediatr VL - 16 IS - 2 N2 - OBJECT Osseous anomalies of the craniocervical junction are hypothesized to precipitate the hindbrain herniation observed in Chiari I malformation (CM-I). Previous work by Tubbs et al. showed that posterior angulation of the odontoid process is more prevalent in children with CM-I than in healthy controls. The present study is an external validation of that report. The goals of our study were 3-fold: 1) to externally validate the results of Tubbs et al. in a different patient population; 2) to compare how morphometric parameters vary with age, sex, and symptomatology; and 3) to develop a correlative model for tonsillar ectopia in CM-I based on these measurements. METHODS The authors performed a retrospective review of 119 patients who underwent posterior fossa decompression with duraplasty at the Monroe Carell Jr. Children's Hospital at Vanderbilt University; 78 of these patients had imaging available for review. Demographic and clinical variables were collected. A neuroradiologist retrospectively evaluated preoperative MRI examinations in these 78 patients and recorded the following measurements: McRae line length; obex displacement length; odontoid process parameters (height, angle of retroflexion, and angle of retroversion); perpendicular distance to the basion-C2 line (pB-C2 line); length of cerebellar tonsillar ectopia; caudal extent of the cerebellar tonsils; and presence, location, and size of syringomyelia. Odontoid retroflexion grade was classified as Grade 0, > 90°; Grade I,85°-89°; Grade II, 80°-84°; and Grade III, < 80°. Age groups were defined as 0-6 years, 7-12 years, and 13-17 years at the time of surgery. Univariate and multivariate linear regression analyses, Kruskal-Wallis 1-way ANOVA, and Fisher's exact test were performed to assess the relationship between age, sex, and symptomatology with these craniometric variables. RESULTS The prevalence of posterior odontoid angulation was 81%, which is almost identical to that in the previous report (84%). With increasing age, the odontoid height (p < 0.001) and pB-C2 length (p < 0.001) increased, while the odontoid process became more posteriorly inclined (p = 0.010). The pB-C2 line was significantly longer in girls (p = 0.006). These measurements did not significantly correlate with symptomatology. Length of tonsillar ectopia in pediatric CM-I correlated with an enlarged foramen magnum (p = 0.023), increasing obex displacement (p = 0.020), and increasing odontoid retroflexion (p < 0.001). CONCLUSIONS Anomalous bony development of the craniocervical junction is a consistent feature of CM-I in children. The authors found that the population at their center was characterized by posterior angulation of the odontoid process in 81% of cases, similar to findings by Tubbs et al. (84%). The odontoid process appeared to lengthen and become more posteriorly inclined with age. Increased tonsillar ectopia was associated with more posterior odontoid angulation, a widened foramen magnum, and an inferiorly displaced obex. SN - 1933-0715 UR - https://www.unboundmedicine.com/medline/citation/26053869/Posterior_odontoid_process_angulation_in_pediatric_Chiari_I_malformation:_an_MRI_morphometric_external_validation_study_ L2 - https://thejns.org/doi/10.3171/2015.1.PEDS14475 DB - PRIME DP - Unbound Medicine ER -