Roller Lauren A, Bruce Beau B, Saindane Amit M
1 Division of Neuroradiology, Department of Radiology and Imaging Sciences, Emory University School of Medicine, BG22, 1364 Clifton Rd NE, Atlanta, GA 30322.
AJR Am J Roentgenol. 2015 Apr;204(4):835-41. doi: 10.2214/AJR.14.13384.
Measurement of posterior fossa volume has been proposed to have diagnostic utility and physiologic significance in the Chiari malformation type 1. This study evaluated the effects of demographics on posterior fossa volume and total intracranial volume in adult control subjects, adult patients with Chiari malformation type 1, and adult patients with idiopathic intracranial hypertension, who may share some imaging features of patients with Chiari malformation type 1.
Twenty-eight patients with Chiari malformation type 1, 21 patients with idiopathic intracranial hypertension, and 113 control subjects underwent brain MRI including contrast-enhanced 3D gradient-recalled echo (GRE) T1-weighted imaging. Linear measurements of the posterior fossa and intracranial space were obtained. Manual segmentation of the posterior fossa and intracranial space was performed to yield posterior fossa volume and total intracranial volume. Age, sex, race, and body mass index (weight in kilograms divided by the square of height in meters; BMI) were controlled for when comparing cohorts.
Three of the 12 linear measurements significantly predicted total intracranial volume (accounting for 74% of variance), and four predicted posterior fossa volume (54% of variance). Age, race, sex, and BMI each statistically significantly influenced posterior fossa volume and total intracranial volume. No statistically significant differences in posterior fossa volume, total intracranial volume, or ratio of posterior fossa volume to total intracranial volume were seen between the Chiari malformation type 1 group and control group after controlling for demographics. Patients with idiopathic intracranial hypertension were more likely than control subjects to have smaller posterior fossa volumes (odds ratio [OR]=1.81; p=0.01) and larger total intracranial volumes (OR=1.24; p=0.06).
Linear measurements of the posterior fossa are not strong predictors of posterior fossa volume. Age, race, sex, and BMI have statistically significant effects on intracranial measurements that must be considered, particularly with respect to posterior fossa volume in Chiari malformation type 1. Even when these demographic variables are appropriately accounted for, other similarly presenting diseases may show small posterior fossa volumes.
有人提出测量后颅窝容积在1型 Chiari 畸形中具有诊断效用和生理意义。本研究评估了人口统计学因素对成年对照受试者、成年1型 Chiari 畸形患者以及成年特发性颅内高压患者后颅窝容积和总颅内容积的影响，后一类患者可能具有一些与1型 Chiari 畸形患者相同的影像学特征。
28例1型 Chiari 畸形患者、21例特发性颅内高压患者和113例对照受试者接受了脑部MRI检查，包括增强三维梯度回波（GRE）T1加权成像。获得后颅窝和颅内空间的线性测量值。对后颅窝和颅内空间进行手动分割以得出后颅窝容积和总颅内容积。在比较队列时对年龄、性别、种族和体重指数（体重千克数除以身高米数的平方；BMI）进行了控制。
12项线性测量值中的3项可显著预测总颅内容积（占方差的74%），4项可预测后颅窝容积（占方差的54%）。年龄、种族、性别和BMI各自对后颅窝容积和总颅内容积均有统计学上的显著影响。在控制人口统计学因素后，1型 Chiari 畸形组与对照组在后颅窝容积、总颅内容积或后颅窝容积与总颅内容积之比方面未见统计学上的显著差异。特发性颅内高压患者比对照受试者更有可能具有较小的后颅窝容积（优势比[OR]=1.81；p=0.01）和较大的总颅内容积（OR=1.24；p=0.06）。
后颅窝的线性测量不是后颅窝容积的有力预测指标。年龄、种族、性别和BMI对颅内测量值有统计学上的显著影响，必须予以考虑，尤其是对于1型 Chiari 畸形中的后颅窝容积。即使对这些人口统计学变量进行了适当考虑，其他表现相似的疾病可能仍显示后颅窝容积较小。
