Hydrocephalus classification: Difference between revisions
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==Classification == | ==Classification == | ||
*Based on its underlying mechanisms, hydrocephalus can be classified into: | *Based on its underlying mechanisms, hydrocephalus can be classified into: | ||
**Communicating (non-obstructive) | **Communicating (non-obstructive). | ||
**Non-communicating (obstructive). | **Non-communicating (obstructive). | ||
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=== 1. Communicating hydrocephalus === | === 1. Communicating hydrocephalus === | ||
*Communicating hydrocephalus, also known as non-obstructive hydrocephalus, | |||
*It is caused by impaired [[cerebrospinal fluid]] resorption in the absence of any [[CSF]]-flow obstruction. | *It is caused by impaired [[cerebrospinal fluid]] resorption in the absence of any [[CSF]]-flow obstruction. | ||
*It has been theorized that this is due to functional impairment of the [[arachnoid granulations]]. | *It has been theorized that this is due to functional impairment of the [[arachnoid granulations]]. | ||
*[[Arachnoid granulations]] are located along the [[superior sagittal sinus]] and is the site of [[cerebrospinal fluid]] resorption back into the [[venous]] system. | *[[Arachnoid granulations]] are located along the [[superior sagittal sinus]] and is the site of [[cerebrospinal fluid]] resorption back into the [[venous]] system. | ||
*Various [[Neurological|neurologic]] conditions may result in communicating hydrocephalus, including | *Various [[Neurological|neurologic]] conditions may result in communicating hydrocephalus, including: | ||
**[[Subarachnoid space|Subarachnoid]]/[[intraventricular hemorrhage]] | **[[Subarachnoid space|Subarachnoid]]/[[intraventricular hemorrhage]] | ||
**[[Meningitis]] | **[[Meningitis]] | ||
Revision as of 04:12, 19 August 2018
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Syed Ahsan Hussain, M.D.[2]
Overview
Hydrocephalus is classified based upon the underlying cause such as impaired cerebrospinal fluid (CSF) flow, impaired CSF reabsorption, or excessive CSF production.
Classification
- Based on its underlying mechanisms, hydrocephalus can be classified into:
- Communicating (non-obstructive).
- Non-communicating (obstructive).
- Both communicating and non-communicating forms can be either:
- Congenital.
- Acquired.
1. Communicating hydrocephalus
- Communicating hydrocephalus, also known as non-obstructive hydrocephalus,
- It is caused by impaired cerebrospinal fluid resorption in the absence of any CSF-flow obstruction.
- It has been theorized that this is due to functional impairment of the arachnoid granulations.
- Arachnoid granulations are located along the superior sagittal sinus and is the site of cerebrospinal fluid resorption back into the venous system.
- Various neurologic conditions may result in communicating hydrocephalus, including:
- Subarachnoid/intraventricular hemorrhage
- Meningitis
- Chiari malformation
- Congenital absence of arachnoidal granulations (Pacchioni's granulations)
Sub-types of communicating hydrocephalus
(a) Normal pressure hydrocephalus (NPH)
- NPH is a particular form of communicating hydrocephalus, characterized by enlarged cerebral ventricles, with only intermittently elevated cerebrospinal fluid pressure.
- The diagnosis of NPH can be established only with the help of continuous intraventricular pressure recordings (over 24 hours or even longer
- Altered compliance (elasticity) of the ventricular walls, as well as increased viscosity of the cerebrospinal fluid, may play a role in the pathogenesis of normal pressure hydrocephalus.
(b) Hydrocephalus ex vacuo
- It refers to an enlargement of cerebral ventricles and subarachnoid spaces, and is usually due to brain atrophy (as it occurs in dementias), post-traumatic brain injuries and even in some psychiatric disorders, such as schizophrenia
- Hydrocephalus ex vacuo occurs as a result of compensatory enlargement of the CSF-spaces in response to brain parenchyma loss - it is not the result of increased CSF pressure.
2. Non-communicating hydrocephalus
Non-communicating hydrocephalus, or obstructive hydrocephalus, is caused by a CSF-flow obstruction (either due to external compression or intraventricular mass lesions).
- Foramen of Monro obstruction may lead to dilation of one or, if large enough (e.g., in colloid cyst), both lateral ventricles.
- The aqueduct of Sylvius, normally narrow to begin with, may be obstructed by a number of genetically or acquired lesions (e.g., atresia, ependymitis, hemorrhage, tumor) and lead to dilatation of both lateral ventricles as well as the third ventricle.
- Fourth ventricle obstruction will lead to dilatation of the aqueduct as well as the lateral and third ventricles.
- The foramina of Luschka and foramen of Magendie may be obstructed due to congenital failure of opening (e.g., Dandy-Walker malformation).
- The subarachnoid space surrounding the brainstem may also be obstructed due to inflammatory or hemorrhagic fibrosing meningitis, leading to widespread dilatation, including the fourth ventricle.
Congenital hydrocephalus
The cranial bones fuse by the end of the third year of life. For head enlargement to occur, hydrocephalus must occur before then. The causes are usually genetic but can also be acquired and usually occur within the first few months of life, which include
- Intraventricular matrix hemorrhages in premature infants
- Infections
- Type II Arnold-Chiari malformation
- Aqueduct atresia and stenosis
- Dandy-Walker malformation.
About 80-90% of fetuses or newborn infants with spina bifida - often associated with meningocele or myelomeningocele- develop hydrocephalus.
Acquired hydrocephalus
This condition is acquired as a consequence of:
- Infections
- meningitis
- brain tumors
- head trauma
- intracranial hemorrhage (subarachnoid or intraparenchymal) and is usually extremely painful for the patient.
| Communicating (non-obstructive) | Non-Communicating (non-obstructive) | Congenital hydrocephalus | Acquired hydrocephalus | |
|---|---|---|---|---|
| subarachnoid/intraventricular hemorrhage | colloid cyst Foramen of Monro obstruction | intraventricular matrix hemorrhages in premature infants | infections | |
| meningitis | atresia of aqueduct of Sylvius | infections | meningitis | |
| Chiari malformation | ependymitis | type II Arnold-Chiari malformation | brain tumors | |
| congenital absence of arachnoidal granulations | hemorrhage | aqueduct atresia and stenosis | head trauma | |
| Normal pressure hydrocephalus | tumor | Dandy-Walker malformation. | Subarachnoid hemorrhage | |
| brain atrophy | Dandy-Walker malformation | spina bifida | ||
| post-traumatic brain injuries | hemorrhagic fibrosing meningitis | meningocele | ||
| psychiatric disorders, such as schizophrenia | myelomeningocele |