Difference between revisions of "CNS Congenital Abnormalities - Pathology"

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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 alwaus 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]]

Revision as of 11:09, 18 August 2008

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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 alwaus crania bifida (a split skull).
  • Meningoencephalocoele may be inherited in pigs and cats.

Hydrocephalus

Hydrocephalus in situ
Hydrocephalus. Image courtesy of BioMed Archive.
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 ventricles
      • The most common type.
      • There is unilateral or bilateral dilation of the ventricles.
    • External hydrocephalus - fluid is within the arachnoid space
    • Communicating hydrocephalus - fluid is within the ventricles and arachnoid space
    • Hydrocephalus ex vacuo - the ventricle is dilated secondary to loss of cerebral tissue
      • Also known as compensatory 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

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