The odontoid process invagination in normal subjects, Chiari malformation and Basilar invagination patients: Pathophysiologic correlations with angular craniometry.

Ricardov Botelho,Jânioa Ferreira

doi:10.4103/2152-7806.160322

Abstract

Background:Craniometric studies have shown that both Chiari malformation (CM) and basilar invagination (BI) belong to a spectrum of malformations. A more precise method to differentiate between these types of CVJM is desirable. The Chamberlain's line violation (CLV) is the most common method to identify BI. The authors sought to clarify the real importance of CLV in the spectrum of craniovertebral junction malformations (CVJM) and to identify possible pathophysiological relationships.Methods:We evaluated the CLV in a sample of CVJM, BI, CM patients and a control group of normal subjects and correlated their data with craniocervical angular craniometry.Results:A total of 97 subjects were studied: 32 normal subjects, 41 CM patients, 9 basilar invagination type 1 (BI1) patients, and 15 basilar invagination type 2 (BI2) patients. The mean CLV violation in the groups were: The control group, 0.16 ± 0.45 cm; the CM group, 0.32 ± 0.48 cm; the BI1 group, 1.35 ± 0.5 cm; and the BI2 group, 1.98 ± 0.18 cm. There was strong correlation between CLV and Boogard's angle (R = 0.82, P = 0.000) and the clivus canal angle (R = 0.7, P = 0.000).Conclusions:CM's CLV is discrete and similar to the normal subjects. BI1 and BI2 presented with at least of 0.95 cm CLV and these violations were strongly correlated with a primary cranial angulation (clivus horizontalization) and an acute clivus canal angle (a secondary craniocervical angle).

Highlights

Craniometric studies have shown that both Chiari malformation (CM) and basilar invagination (BI) belong to a spectrum of malformations
Craniometric studies have shown that both of these malformations belong to a spectrum of malformations whose common characteristic is the underdevelopment of the occipital bone and consequent neural and cerebrospinal fluid (CSF) flow compression at the craniocervical junction
Increasing evidence has identified two subgroups of BI: One is associated with craniovertebral instability in which the tip of the odontoid process projects inside the foramen magnum,[7,8,10,11,17,19,21,24] and the other is not associated with instability, but with greater cranial deformity [Figures 2 and 3]

Summary

Methods

We evaluated the CLV in a sample of CVJM, BI, CM patients and a control group of normal subjects and correlated their data with craniocervical angular craniometry. This study was approved by the Research Ethics Committee (Instituto de Assistencia Médica ao Servidor Público Estadual – sp‐caae07284212000005463). To study the degree of odontoid process invagination, we evaluated magnetic resonance imaging (MRI) scans of the craniocervical junction in T1 and T2 midline sagittal scan acquisitions from a CVJM patient sample consecutively treated by the authors between 1996 and 2012. The measurements were performed by an observer who was unaware of other study data. Patients with CVJM were divided into three groups: CM patients, basilar invagination type 1 (BI1) patients and basilar invagination type 2 (BI2) patients.[1,6].

Results

Discussion

Conclusion