Angular craniometry in craniocervical junction malformation

Abstract

The craniometric linear dimensions of the posterior fossa have been relatively well studied, but angular craniometry has been poorly studied and may reveal differences in the several types of craniocervical junction malformation. The objectives of this study were to evaluate craniometric angles compared with normal subjects and elucidate the main angular differences among the types of craniocervical junction malformation and the correlation between craniocervical and cervical angles. Angular craniometries were studied using primary cranial angles (basal and Boogard's) and secondary craniocervical angles (clivus canal and cervical spine lordosis). Patients with basilar invagination had significantly wider basal angles, sharper clivus canal angles, larger Boogard's angles, and greater cervical lordosis than the Chiari malformation and control groups. The Chiari malformation group does not show significant differences when compared with normal controls. Platybasia occurred only in basilar invagination and is suggested to be more prevalent in type II than in type I. Platybasic patients have a more acute clivus canal angle and show greater cervical lordosis than non-platybasics. The Chiari group does not show significant differences when compared with the control, but the basilar invagination groups had craniometric variables significantly different from normal controls. Hyperlordosis observed in the basilar inavagination group was associated with craniocervical kyphosis conditioned by acute clivus canal angles.

Fig. 1

Examples of BI type I. The tip of the dens is inside the foramen magnum

Fig. 2

BI type II. The tip of the dens stops in osseous structures, preventing upward migration (arrows)

Fig. 3

Left Primary angles: basal and Boogard’s angles. Right Secondary angles: clivus canal and cervical lordosis angles

Fig. 4

MRI image of the four studied groups. Upper left Normal subject. Upper right Chiari malformation. Lower left Basilar invagination I (BI I). Lower right BI II

Fig. 5

Illustration based on the average craniometric angles depicting the four CCJM subgroups. CTRL normal individuals, CM Chiari malformation, BI I basilar invagination type I, BI II basilar invagination type II

Fig. 6

Graphic illustrations of basilar invagination angles with and without platybasia. ccPLT clivus canal angle of the platybasic group, ccNPLT clivus canal angle of the non-platybasic group, BooPLT Boogard’s angle of the non-platybasic group, BooNPLT Boogard’s angle of the platybasic group, CLPLT cervical lordosis of the platybasic group, CLNPLT cervical lordosis of the non-platybasic group