Epidemiology
Etiology
Noncommunicating hydrocephalus (obstructive hydrocephalus)
Obstruction of the cerebral aqueduct of Sylvius, the lateral foramen of Luschka, or the median foramen of Magendie results in obstructed passage of CSF from the ventricles to the subarachnoidal space. See Ventricular system
- Congenital: Noncommunicating hydrocephalus is the most common form of congenital hydrocephalus.
- Arnold-Chiari malformation
- Dandy-Walker malformation: congenital malformation caused by failure of the fourth ventricle to close, which leads to persistence of Blake’s pouch (cyst in the 4th ventricle) and cerebellar vermis hypoplasia
- Causes a variety of neurologic abnormalities (e.g., ataxic gait) and noncommunicating hydrocephalus
- Associated with a variety of extracranial abnormalities (e.g., craniofacial abnormalities, cardiac defects, spina bifida)
- Intrauterine infections: e.g., congenital toxoplasmosis (see Congenital TORCH infections)
- Colloid cyst obstructing the interventricular foramen
- Congenital stenosis of the cerebral aqueduct of Sylvius
- Acquired
- Brain tumor (especially medulloblastomas, pinealoma, ependymomas, and astrocytomas)
Chiari malformation vs Dandy-Walker malformation
Feature Chiari Malformation Dandy-Walker Malformation Pathophysiology Cerebellum herniates through foramen magnum due to small posterior fossa. Agenesis of cerebellar vermis allows 4th ventricle to enlarge into a cyst. Posterior Fossa Small / Normal Enlarged Key Abnormality Tonsillar (Type I) or vermis + tonsillar (Type II) herniation. Absent cerebellar vermis. Hydrocephalus Common, due to CSF outflow obstruction. Very common, due to cystic 4th ventricle. Key Associations - Type I: Syringomyelia.
- Type II: Myelomeningocele.Hydrocephalus, Spina Bifida, Agenesis of corpus callosum. Typical Presentation - Type I: Adult w/ headaches.
- Type II: Infant w/ brainstem dysfunction.Infant w/ macrocephaly. Chiari畸形：过度拥挤的房间
请把后颅窝想象成一个小卧室，把小脑和脑干想象成里面的家具。
- 问题所在： 在Chiari畸形中，这个房间建得太小了，无法容纳所有它需要放置的家具。
- 后果： 为了把所有东西都塞进去，一部分家具（小脑扁桃体）被挤了出来，并从唯一的开口——门道（枕骨大孔）——伸了出去。
- 结果： 这些堵在门口的家具阻碍了交通（脑脊液流动），导致房间内压力积聚（脑积水），并影响到走廊的墙壁（脊髓空洞症）。
核心：Chiari是一个_拥挤_问题。
Dandy-Walker畸形：缺失的帐篷支柱
请把后颅窝想象成一个大帐篷，把小脑蚓部想象成它主要的中央支撑柱。
- 问题所在： 在Dandy-Walker畸形中，这根中央帐篷支柱缺失了（蚓部发育不全）。
- 后果： 没有了支柱的支撑，帐篷的顶部（第四脑室）无法正常成型。它会塌陷并被“雨水”（脑脊液）充满，形成一个巨大的、充满液体的囊肿。
- 结果： 这个不断膨胀的水囊肿将帐篷壁向外推（后颅窝扩大），并堵住了拉链出口（脑脊液流出道），将所有的水都困在里面，导致整个帐篷都肿胀起来（脑积水）。
核心：Dandy-Walker是一个_结构缺陷_问题。
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Pathophysiology
Clinical features
Diagnostics
Treatment
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