Department of Radiology and Imaging Sciences, Emory University, Atlanta, Georgia 30322, USA.
AJNR Am J Neuroradiol. 2012 Nov;33(10):1901-6. doi: 10.3174/ajnr.A3068. Epub 2012 Jun 21.
IIH is a syndrome of elevated intracranial pressure without hydrocephalus, mass, or identifiable cause. Diagnosis is made by clinical presentation, intracranial pressure measurement, and supportive imaging findings. A subset of patients with IIH may have tonsillar ectopia, meeting the criteria for Chiari malformation type I but not responding to surgical decompression for Chiari I. The purpose of this study was to determine the incidence and morphology of cerebellar tonsillar ectopia in patients with IIH.
Forty-three patients with clinically confirmed IIH and 44 age-matched controls were included. Two neuroradiologists with CAQs reviewed sagittal T1-weighted MRI in a blinded fashion and measured cerebellar tonsil and obex positions relative to the foramen magnum and prepontine cistern width at the level of the midpons.
Nine of 43 patients with IIH and 1/44 controls had cerebellar tonsillar ectopia of ≥5 mm. Five of 9 of patients with IIH with ectopia of ≥5 mm also had a "peglike" tonsil configuration. Patients with IIH had a significantly lower tonsillar position (2.1 ± 2.8 mm) than age-matched controls (0.7 ±1.9 mm, P < .05). The obex position was significantly lower in patients with IIH versus controls (-7.9 mm [above the FM] versus -9.4 mm [above the FM], P < .05). The prepontine width was not significantly different between the groups.
Cerebellar tonsil position in patients with IIH was significantly lower than that in age-matched controls, often times peglike, mimicking Chiari I. A significantly lower obex position suggests an inferiorly displaced brain stem and cerebellum. When tonsillar ectopia of >5 mm is identified, imaging and clinical consideration of IIH are warranted to avoid misdiagnosis as Chiari I.
IIH 是一种颅内压升高而无脑积水、肿块或可识别病因的综合征。通过临床表现、颅内压测量和支持性影像学发现来诊断。IIH 的一部分患者可能存在扁桃体异位，符合 Chiari 畸形 I 型的标准，但对 Chiari I 型的减压手术无反应。本研究的目的是确定 IIH 患者小脑扁桃体异位的发生率和形态。
纳入 43 例经临床证实的 IIH 患者和 44 名年龄匹配的对照者。两名具有 CAQ 的神经放射科医生以盲法对矢状 T1 加权 MRI 进行了复查，并测量了小脑扁桃体和枕骨大孔的位置，以及中脑水平桥前池的宽度。
43 例 IIH 患者中有 9 例和 44 例对照者中有 1 例存在小脑扁桃体异位 ≥5mm。9 例 IIH 患者中，有 5 例存在异位 ≥5mm 的“钉状”扁桃体形态。IIH 患者的扁桃体位置明显低于年龄匹配的对照组（2.1 ± 2.8mm 比 0.7 ±1.9mm，P<.05）。与对照组相比，IIH 患者的枕骨大孔位置明显更低（枕骨大孔以上 -7.9mm 比 -9.4mm，P<.05）。两组间桥前池宽度无显著差异。
IIH 患者的小脑扁桃体位置明显低于年龄匹配的对照组，常常呈钉状，类似于 Chiari I。枕骨大孔位置较低提示脑干和小脑向下移位。当发现扁桃体异位 >5mm 时，需要进行影像学和临床检查以考虑 IIH，避免误诊为 Chiari I。
