Sener R N
Department of Radiology, Ege University Hospital, Bornova, Izmir, Turkey.
Comput Med Imaging Graph. 1995 Nov-Dec;19(6):491-4. doi: 10.1016/0895-6111(96)00002-x.
The subjects in this study cover seven selected patients-four with Chiari II malformation associated with a vanishing cerebellum and three with primary cerebellar agenesis-and the main radiological (MR imaging) differences between the two are discussed. The reason for this discussion is that some authors consider primary cerebellar agenesis as a type of Chiari malformations, and refer to it as Chiari IV malformation. Primary cerebellar agenesis can be distinguished from the Chiari II malformation associated with a vanishing cerebellum by presence of a relatively normal-sized posterior fossa, identification of symmetrical remnants of the anterior quadrangular lobules, by lack of scattered remnants of cerebellar tissue, and by presence of a normal brain and spine. The only common finding in both conditions is a small brainstem with loss of normal pontine configuration. Considering the previous descriptions of anatomical changes related to the so-called Chiari IV malformation which include absent cerebellum, and large posterior fossa cerebrospinal fluid spaces, it is probable that many of the cases previously considered as Chiari IV malformation were unrelated to any type of Chiari malformations, and actually represented primary cerebellar agenesis.
本研究的对象包括七名选定患者——四名患有与小脑消失相关的Chiari II型畸形，三名患有原发性小脑发育不全——并讨论了两者之间主要的影像学（磁共振成像）差异。进行此讨论的原因是，一些作者将原发性小脑发育不全视为Chiari畸形的一种类型，并将其称为Chiari IV型畸形。原发性小脑发育不全可通过相对正常大小的后颅窝、前四边形小叶对称残余的识别、小脑组织无散在残余以及正常的脑和脊柱来与伴有小脑消失的Chiari II型畸形相区分。两种情况唯一的共同发现是脑干小且桥脑正常形态消失。考虑到先前对与所谓Chiari IV型畸形相关的解剖学变化的描述，包括小脑缺失和后颅窝脑脊液间隙增大，很可能许多先前被认为是Chiari IV型畸形的病例与任何类型的Chiari畸形无关，实际上代表原发性小脑发育不全。
