Difference between revisions of "CNS Congenital Abnormalities - Pathology"

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#redirect[[:Category:Central Nervous System - Congenital Abnormalities]]
 
 
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==Introduction==
 
 
 
* Congenital malformations may involve the spinal cord, brain, meninges, calvaria or vertebral column.
 
* Abnormalities typically result from defects in neural tube development. 
 
* Congenital malformations are present at or before birth, and manifest as either:
 
** Morphological problems
 
** Functional problems
 
*** Tend to arise as biochemical abnormalities, such as the lysosomal diseases or leukodystrophies.
 
* Causes of congenital abnormalities include:
 
** Environmental causes
 
*** For example, these may be toxic, infectious, nutritional, or physical (e.g. radiation)
 
*** This is by far the most common cause.
 
** Inherited traits.
 
 
 
==Meningoencephalocoele==
 
 
 
* A defect in the cranium allows protrustion of the brain and meninges.
 
** There is always crania bifida (a split skull).
 
* Meningoencephalocoele may be inherited in pigs and cats.
 
 
 
==Hydrocephalus==
 
[[Image:hydrocephalus.jpg|thumb|right|150px|Hydrocephalus in situ]] [[Image:hydrocephalussection.jpg|thumb|right|150px|Hydrocephalus. Image courtesy of BioMed Archive.]] [[Image:aqueductstenosis.jpg|thumb|right|150px|Aqueduct stenosis. Image courtesy of BioMed Archive.]]
 
* Hydrocephalus is an increased accumulation of fluid in the cranial cavity.
 
* There are several different types of hydrocephalus relating to where the fluid is located within the cavity.
 
** '''Internal''' hydrocephalus - fluid is within the <u>ventricles</u>
 
*** The most common type.
 
*** There is unilateral or bilateral dilation of the ventricles.
 
** '''External''' hydrocephalus - fluid is within the <u>arachnoid space</u>
 
** '''Communicating''' hydrocephalus - fluid is within the <u>ventricles and arachnoid space</u>
 
** '''Hydrocephalus ex vacuo''' - the <u>ventricle is dilated secondary to loss of cerebral tissue</U>
 
*** Also known as compensatory hydrocephalus.
 
 
 
[http://w3.vet.cornell.edu/nst/nst.asp?Fun=F_KSsrch&kw=HYDROCEPHALUS View images courtesy of Cornell Veterinary Medicine]
 
 
 
===Causes===
 
 
 
* Hydrocephalus may be '''congenital'''.
 
** Congenital hydrocephalus is common in brachycephalic and small breed dogs.
 
*** It occurs sporadically in cattle.
 
** Obstructive lesions are often not found.
 
** Amalformed mesencephalic aqueduct may be involved.
 
** The cranium may be abnormal, for example, doming.
 
* '''Acquired''' hydrocephalus is  the result of obstruction, usually due to inflammation or compression.
 
** Space-occupying lesions include :
 
*** Neoplasms
 
*** Abscesses
 
*** Cholesteatomas
 
** Inflammation of meninges and/or ependymal cells can lead to hydrocephalus.
 
*** For example,  FIP causes ependymitis which can obstruct flow if it affects the mesencephalic aqueduct.
 
* Hydrocephalus may also arise with:
 
** Increased ventricle size due to loss of brain parenchyma.
 
** Overproduction of CSF
 
*** Rare
 
*** Associated with choroid plexus tumours.
 
 
 
===Breed predisposition===
 
 
* Some breeds are predisposed to hydrocephalus.
 
** Chihuahua, pomeranian, yorkshire terrier, english bulldog, lhasa apso, toy poodle, cairn terrier, boston terrier, pug, pekingese, maltese terrier.
 
** Hydrocephalus has also been described in
 
*** Bullmastiffs, in association with cerebellar ataxia.
 
*** Siamese cats, as an autosomal recessive trait.
 
 
 
===Clinical Signs===
 
 
 
* Clinical signs are the result of:
 
** Loss of neurons or neuronal function
 
** Alterations in intercranial pressure
 
** Pathophysiological effects of intracranial disease
 
* Signs reflect the anatomical level of disease involvement.
 
** Rostrotentorial, vestibular and cerebellar signs are most common.
 
* Signs are not related to the degree of ventricular dilation. They are more associated with other damage caused by the disease proces:
 
** Intracranial pressure changes
 
** Intraventricular haemorrhage
 
** Speed of ventricular obstruction
 
* Hydrocephalus may contribute to abnormalities of skull development, where it is a congenital disease.
 
** Thinning of the bone structure
 
** Dome-shape head
 
** Persistent fontanelles
 
* Ventral or lateral strabismus may occur, although the reason for this is unknown.
 
** May be related to distortion of the orbits, due to skill deformity.
 
** May be realted with pressue on the mesencephalic tegementum.
 
 
 
===Diagnosis===
 
 
 
* Diagnosis is by a variety of imaging and electrophysiologic methods.
 
** MRI allows examination of the ventricular system, and give better resolution of the brain parenchyma than CT.
 
 
 
===Treatment===
 
 
 
* Prognosis is generally poor.
 
* Medical treatment:
 
** General supportive care
 
** Medications to limit CSF production and reduce intracranial pressure.
 
* Surgical treatment:
 
** Aims to allow drainage of CSF from the brain to another site for absorption.
 
 
 
==Cerebellar Defects==
 
 
 
* Cerebellar defects include:
 
** [[Cerebellar Pathology - Pathology#Cerebellar Hypoplasia|Cerebellar hypoplasia]]
 
** [[Cerebellar Pathology - Pathology#Cerebellar Abiotrophy|Cerebellar abiotrophy]]
 

Latest revision as of 13:13, 8 March 2011