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| − | {{review}}
| + | #redirect[[:Category:Central Nervous System - Congenital Abnormalities]] |
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| − | {{toplink
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| − | |backcolour = E0EEEE
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| − | |linkpage = Nervous System - Pathology
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| − | |linktext =Nervous System
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| − | |maplink = Nervous System (Content Map) - Pathology
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| − | |pagetype =Pathology
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| − | }}
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| − | <br>
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| − | ==Introduction==
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| − | * Congenital malformations may involve the spinal cord, brain, meninges, calvaria or vertebral column.
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| − | * Abnormalities typically result from defects in neural tube development.
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| − | * Congenital malformations are present at or before birth, and manifest as either:
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| − | ** Morphological problems
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| − | ** Functional problems
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| − | *** Tend to arise as biochemical abnormalities, such as the lysosomal diseases or leukodystrophies.
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| − | * Causes of congenital abnormalities include:
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| − | ** Environmental causes
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| − | *** For example, these may be toxic, infectious, nutritional, or physical (e.g. radiation)
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| − | *** This is by far the most common cause.
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| − | ** Inherited traits.
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| − | ==Meningoencephalocoele==
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| − | * A defect in the cranium allows protrustion of the brain and meninges.
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| − | ** There is always crania bifida (a split skull).
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| − | * Meningoencephalocoele may be inherited in pigs and cats.
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| − | ==Hydrocephalus==
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| − | [[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.
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| − | * There are several different types of hydrocephalus relating to where the fluid is located within the cavity.
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| − | ** '''Internal''' hydrocephalus - fluid is within the <u>ventricles</u>
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| − | *** The most common type.
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| − | *** There is unilateral or bilateral dilation of the ventricles.
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| − | ** '''External''' hydrocephalus - fluid is within the <u>arachnoid space</u>
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| − | ** '''Communicating''' hydrocephalus - fluid is within the <u>ventricles and arachnoid space</u>
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| − | ** '''Hydrocephalus ex vacuo''' - the <u>ventricle is dilated secondary to loss of cerebral tissue</U>
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| − | *** Also known as compensatory hydrocephalus.
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| − | [http://w3.vet.cornell.edu/nst/nst.asp?Fun=F_KSsrch&kw=HYDROCEPHALUS View images courtesy of Cornell Veterinary Medicine]
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| − | ===Causes===
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| − | * Hydrocephalus may be '''congenital'''.
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| − | ** Congenital hydrocephalus is common in brachycephalic and small breed dogs.
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| − | *** It occurs sporadically in cattle.
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| − | ** Obstructive lesions are often not found.
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| − | ** Amalformed mesencephalic aqueduct may be involved.
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| − | ** The cranium may be abnormal, for example, doming.
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| − | * '''Acquired''' hydrocephalus is the result of obstruction, usually due to inflammation or compression.
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| − | ** Space-occupying lesions include :
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| − | *** Neoplasms
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| − | *** Abscesses
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| − | *** Cholesteatomas
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| − | ** Inflammation of meninges and/or ependymal cells can lead to hydrocephalus.
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| − | *** For example, FIP causes ependymitis which can obstruct flow if it affects the mesencephalic aqueduct.
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| − | * Hydrocephalus may also arise with:
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| − | ** Increased ventricle size due to loss of brain parenchyma.
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| − | ** Overproduction of CSF
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| − | *** Rare
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| − | *** Associated with choroid plexus tumours.
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| − | ===Breed predisposition===
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| − | * Some breeds are predisposed to hydrocephalus.
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| − | ** Chihuahua, pomeranian, yorkshire terrier, english bulldog, lhasa apso, toy poodle, cairn terrier, boston terrier, pug, pekingese, maltese terrier.
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| − | ** Hydrocephalus has also been described in
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| − | *** Bullmastiffs, in association with cerebellar ataxia.
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| − | *** Siamese cats, as an autosomal recessive trait.
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| − | ===Clinical Signs===
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| − | * Clinical signs are the result of:
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| − | ** Loss of neurons or neuronal function
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| − | ** Alterations in intercranial pressure
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| − | ** Pathophysiological effects of intracranial disease
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| − | * Signs reflect the anatomical level of disease involvement.
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| − | ** Rostrotentorial, vestibular and cerebellar signs are most common.
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| − | * Signs are not related to the degree of ventricular dilation. They are more associated with other damage caused by the disease proces:
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| − | ** Intracranial pressure changes
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| − | ** Intraventricular haemorrhage
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| − | ** Speed of ventricular obstruction
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| − | * Hydrocephalus may contribute to abnormalities of skull development, where it is a congenital disease.
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| − | ** Thinning of the bone structure
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| − | ** Dome-shape head
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| − | ** Persistent fontanelles
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| − | * Ventral or lateral strabismus may occur, although the reason for this is unknown.
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| − | ** May be related to distortion of the orbits, due to skill deformity.
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| − | ** May be realted with pressue on the mesencephalic tegementum.
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| − | ===Diagnosis===
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| − | * Diagnosis is by a variety of imaging and electrophysiologic methods.
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| − | ** MRI allows examination of the ventricular system, and give better resolution of the brain parenchyma than CT.
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| − | ===Treatment===
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| − | * Prognosis is generally poor.
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| − | * Medical treatment:
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| − | ** General supportive care
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| − | ** Medications to limit CSF production and reduce intracranial pressure.
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| − | * Surgical treatment:
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| − | ** Aims to allow drainage of CSF from the brain to another site for absorption.
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| − | ==Cerebellar Defects==
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| − | * Cerebellar defects include:
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| − | ** [[Cerebellar Pathology - Pathology#Cerebellar Hypoplasia|Cerebellar hypoplasia]]
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| − | ** [[Cerebellar Pathology - Pathology#Cerebellar Abiotrophy|Cerebellar abiotrophy]]
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