Chiari type I malformations in young adults: implications for the college health practitioner

Volumetric assessment of Posterior cranial fossa in a West African population

BACKGROUND AND OBJECTIVES

Posterior fossa pathologies can have potentially devastating outcomes. The volumetric capacity of this fossa, known to have ethnoregional variations, can thus be critical in determining outcomes and intervention measures and approaches to pathologies involving this region. This study aimed to evaluate the normal posterior fossa volumes within the West-African subpopulation.

METHODS

This was a descriptive study of all patients presenting for a cranial imaging study at the study location within a two-year period using a 1.5T MRI of this cranial region. Obtained data included the transverse and anteroposterior diameters, and the height of this fossa and the obtained data was analyzed. P values < 0.05 was statistically significant.

RESULTS

A total of 315 patients were recruited (165 males and 150 females). The average posterior fossa transverse diameter, anteroposterior diameter and height were 108.19 mm, 71.58 mm and 35.53 mm respectively for males, and 105.7 mm, 66.48 mm, and 34.24 mm for females respectively. The average posterior fossa volume for males (292.36 cm3) was significantly higher than for females (252.90 cm3) (p= 0.0038). The highest average posterior fossa volume was between 16-30 years for males and above 75 years for females.

CONCLUSION

Posterior cranial fossa volumes for the West African population is significantly higher than those obtained for other regions. In addition to being beneficial in some posterior fossa space occupying lesions, this larger volume can explain the relative rarity and sexual preferences of some posterior fossa congenital abnormalities like Chiari-1 malformation amongst the West African population.

Quantification of Cerebellar Crowding in Type I Chiari Malformation

This study was focused on a semi-automated morphometric analysis of the cerebellum in the mid-sagittal plane as an alternative to tonsillar descent alone in the evaluation of Chiari malformation type 1 (CMI) patients. Morphometric analyses of posterior fossa structures were performed on mid-sagittal MRI images of 375 individuals (females, > 18 years, 235 CMI and 140 healthy controls). Twenty-six parameters including linear, angular and area measurements together with non-dimensional ratios were calculated. Eighteen parameters were found to be significantly different between CMI and control subjects. Smaller posterior cranial fossa (PCF) area in CMI subjects was attributed to a smaller PCF area anterior to the brainstem. The cerebellar area was found to be larger in CMI subjects as compared to controls (15.1%), even without inclusion of the tonsillar area below the foramen magnum (FM) (8.4%). The larger cerebellar area in CMI subjects was due to cranial-caudal elongation of the cerebellum, predominately below the fastigium. The cerebrospinal fluid spaces below the FM were smaller in CMI subjects as compared to controls. Overall, greater cerebellar crowding was identified in CMI subjects relative to healthy controls. These observations may improve our understanding of the pathophysiology of CMI in adult female patients.