Difference between revisions of "Congenital and Neonatal Disease - Pathology"
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Revision as of 19:14, 20 September 2010
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Introduction
- Changes in the patterns of growth and differentation result in growth disorders.
- These changes may be in single cells, tissues or organs.
- There are two types of growth disorders.
- Malformations
- Occur during gestation.
- Congenital
- Detected at birth.
- Malformations
- Some growth disorders have a heriditary input.
- Occur as a result of genetically transmitted disease.
- Some growth disorders occur as a sequl to a variety of insults to the foetus during gestation.
- Only a few malformations are readily accessible to surgical correction.
Causes of Malformations
- There are many causes of malformations in animals.
- If the insult occurs early in gestation and is sufficiently severe, it will result in foetal death, resorption and infertility.
- If the insult occurs late in gestation, the malformation will be more limited and the foetus usually survives.
Chromosomal Defects
- Although malformations can be caused by chromosomal abnormalitis, these often result in early abortion or resorption.
Viral Diseases
- Some viruses are able to cross the placenta and cause damage to foetal tissues.
- For example:
- Border Disease Virus in lambs.
- Cerebellar hypoplasia in kittens caused by parvovirus.
Toxins
- For example, toxic plants ingested by the dam during pregnancy.
- Veratrum californicum
- May produce cyclopia in lambs when ingested by the dam in early pregnancy.
- Veratrum californicum
Drugs
- Griseofulvin
- Used to treat "ringworm" (dermatophytosis). ( for the treatment of dermatophytosis - 'ringworm' )
- Can cause serious malformations in kittens if administered to a pregnant queen.
- Oestrogens and Actinomycin D have also been associated with malformations.
Ionising Radiation
- For example, X-rays.
Nutritional Deficiencies
Copper Deficiency
- Copper deficiency in the pregnant ewe can result in "swayback'" in lambs.
- Due to white matter degeneration in the central nervous system of prenatal and neonatal lambs.
- The degeneration is thought to be a mixture of both hypomyelination and demyelination.
- The central nervous system of the lambs is affected.
- Neonatal lambs show an ataxia in the first few weeks of life.
- Due to demyelination of dorsolateral and ventromedial tracts in the white matter of the spinal cord.
- More severe lesions can be present in lambs affected prenatally.
- Destruction of subcortical white matter in the brain.
- The extent of this varies.
- Destruction of subcortical white matter in the brain.
- Neonatal lambs show an ataxia in the first few weeks of life.
- It is unknown how copper deficiency exerts this effect.
- Supplementation in pregnancy prevents the prenatal form.
- Supplementation in the first few weeks will alleviate the neonatal form.
Vitamin Deficiencies
- Vit. A and D deficiency can result in skeletal malformations.
Physical Factors
- For example, adhesions between foetal membranes or umbilical cord.
- Can result in amputation of skeletal segments.
- Especially around limbs.
- Can result in amputation of skeletal segments.
Anoxia
- Lack of oxygen in gestation can result in malformations.
Malformations
Cyclops
- The presence of a single central eye as a result of facial deformity.
Bulldog Calf
- A well recognised deformation in Dexter calves.
- Related to defective cartilage matrix and abnormal ossification.
- The calf is born with short and crooked limbs and the facial bones are short.
Cleft Palate
- A very common malformation in many species.
- Due to failure of the palatine bones to fuse in the midline.
- The animal:
- Fails to suckle properly
- Can develop an aspiration pneumonia.
- Caused by:
- Administration of griseofulvin to queens during pregnancy.
- Certain viral infections.
- Ingestion of toxic plants.
Cystic Kidney
- Also known as polycystic kidney.
- Can be seen in many different species.
- Can have a hereditary basis.
- The cysts may be single or multiple.
- Results from the failure of development of the tubular system in nephrons.
- Severely affected animals may die of renal failure early in life.
- The affected kidney does not have enough functional reserve, and so small infections can have a serious effect on renal function.
Spina Bifida
- A failure of closure of the vertebral arch.
- May result in herniation of the meninges and /or spinal cord.
- There may be a direct communication between those structures and the skin surface.
Hydrocephalus
- Not uncommon in dogsand cats.
- Abnormal drainage of cerebrospinal fluid (CSF) results in dilation of the ventricles of the brain.
- Is a result of either stenosis of:
- The aqueduct between the 3rd and 4th ventricle, or
- The foramina further back in the brain stem.
- May also be acquired as a result of compression by tumours or infectious processes.
- Is a result of either stenosis of:
- Dilation of the ventricles with CSF causes pressure atrophy of the overlying brain tissue.
- Hydrocephalus can be seen at birth.
- Characterised by a dome shaped skull and open fontanelles.
- Hydrocephalus may also be hidden and detected later in life.
Cerebellar Hypoplasia
- The cerebellum is smaller than normal and oftenrudimentary.
- Microscopy shows a highly disorganised architecture.
- The animal shows tremors and ataxia.
- Usually associated with viral infections during gestation.
Skeletal Malformations
- There are numerous skeletal malformations.
- Include:
- Absence of bones
- Deformation
- Shortening
- Duplication
- Hypoplasia
Skin Defects
- E.g. Epitheliogenesis imperfecta.
- There is absence of portions of the epidermis.
- Results in ulcers.
- There is absence of portions of the epidermis.
Muscular Defects
- E.g. defects in the thoracoabdominal walls resulting in exterioration of internal viscera.
- Called "shistosoma".
Cardiac Defects
- There are several possible types of cardiac defects.
- These include:
- Patency between chambers
- Persistent right aortic arch
- Tetrology of Fallot.
- These include:
Sexual Organ Malformation
- E.g.:
- Hermaphrodites
- Pseudohermaphrodites
- Freemartinism in females calves.
Metabolic Diseases
- "Storage" diseases.
- Vital enzymes are missing or defective within all cells.
- These diseases express themselves as storage of intermediate products within cells.
- Because neural tissue is a very sensitive tissue and cannot repair, these diseases usually express themselves as disease of the Central Nervous System.