Congenital Defects
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| Hydrocephalus - Introduction |
Cerebrospinal fluid (CSF) is a watery fluid that is continuously produced and absorbed and it flows in the brain cavities and around the surface of the brain and spinal cord. It protects the central nervous system from injury and cushions it from the surrounding bone structure. CSF also contains glucose, protein and white blood cells from the immune system. Hydrocephalus is the pathological accumulation of CSF in the ventricular system of the brain. It may be either congenital or acquired. Congenital hydrocephalus is most frequently due to an obstruction of CSF flow, either in the ventricular system of the brain or at the point of resorption.
| Incidence |
Congenital hydrocephalus is common in toy breeds (Chihuahua, Manchester Terrier, Pomeranian, Toy Poodle) and in brachycephalic breeds (English Bulldog, Boston Terrier, Pekingese, Lhasa Apso). Hydrocephalus appears to be hereditary in some breeds e.g. Yorkshire Terriers.
| Clinical signs |
The most common clinical signs include seizures, visual deficits, slowed learning and dementia (loss of mental ability). Other signs include an uncoordinated gait, circling, head pressing. Many individuals with congenital hydrocephalus present with an enlarged, dome shaped cranium (upper portion of the skull that protects the brain) and some have open fontanelle (soft spots between the bones of the skull). The signs are usually slowly progressive in individuals with congenital hydrocephalus.
| Diagnosis |
Radiographs are commonly used. Ultrasound may however also be used to demonstrate ventricular enlargement in cases with open fontanelle. Enhanced imaging techniques such as MRI or CT scanning can also confirm the presence of hydrocephalus.
| Treatment |
There has been limited success in the long-term treatment of congenital hydrocephalus with corticosteroids. Surgical drainage has been of benefit in some cases and involves the placement of a shunt. The complications of such surgery in very young patients can however be quite high.
| Epilepsy - Introduction |
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Epilepsy is a condition characterized by recurrent siezures (two or more) due to abnormal and excessive discharge of s aset of neurons (nerve cells) in the brain. the prevalence of epilepsy in the dog population has been estimated between 0,5 to 5,0%.
| Genetics |
Epilepsy can occur in any purebred or mixed dog breed. A familial predisposition has been report for many many breeds, including Beagle, Keeshound, Belgian Tervueren, Golden Retriever, Labrador Retriever, Vizla and Shetland sheepdog. Different modes of inheritance has been suggested for different breeds.
| Diagnosis |
The diagnostic work-up is extensive. The main objective is however not necessarily to reach a precise diagnosis, but rather to rule out conditions that would require or benefit from specific medical or surgical treatment e.g. neoplasia or encephalitis.
| Treatment |
Treatment involves antiepileptic drug therapy.
| Prognosis |
The prognosis will depend on the nature of the underlying cause as well as the response to therapy.
| Afghan Hound Myelopathy - Introduction |
Afghan hound myelopathy is a neurodegenerative disease that is also called Afghan hound hereditary myelopathy. A neurodegenerative disease is a disorder that is caused by the deterioration of certain nerve cells or neurons and changes in these neurons cause them to function abnormally, eventually bringing about their death. Afghan hound myelopathy has an autosomal recessive mode of inheritance the parents of affected individuals therefore have to be carriers. A carrier is an individual that carries one gene for the particular trait, but the carrier does not express the trait (do not show clinical signs of the disease). When the carrier is however mated with another carrier, they can produce offspring that express the trait (show clinical signs of the disease). Typically 25% of male and female dogs in a litter are equally likely to be affected. Diseased animals are therefore generally not used for breeding.
| Clinical signs |
Clinical signs have been noted in dogs between 3 and 13 months of age and the first signs observed include hind limb paresis (a state of slight or temporary paralysis) and ataxia) (loss of power of governing movements). Affected individuals may have a bunny hpping gait. these signs however progess within 1 to 3 weeks to paraplegia (paralysis of the lower part of the body including the legs), front limb paresis and / or tetraplegia (paralyis of all four llimbs). Urinary incontinence is often seen and faecal incontenence may be present in paraplegic dogs. Death frequently results from respiratory failure.
| Treatment |
There is no treatment.
| Prognosis |
The prognosis is poor to grave.
| Peripheral vestibular disorders - Introduction |
The vestibular system has two main functions:
- Maintaining the visual image by stabilizing the eyes in space during head movement
- To stabilize the position of the head in space
The vestibular system thus ensures that the position of the body is table.
Congenital vestibular disease is reported in both purebred dogs and cats. Dog breeds that are commonly affected include the German shepherd, English cocker spaniel, Doberman pinscher, Shetland sheepdog, Akita and Beagle.
Other causes of peripheral vestibular disorders include metabolic causes e.g. hypothyrodism, neoplasia; infectious or inflammatory causes; idiopathic causes; trauma, vascular causes; and toxicity.
| Clinical signs |
Signs are usually unilateral (only affecting one side), however bilateral (signs affecting both sides) are seen in Beagle and Akita. Onset of clinical signs is usually from birth to 3 months of age and includes head tilt, ataxia, some degree of deafness.
| Prognosis |
Prognosis can be favourable with some individuals improving with time due to compensation.
For more information on other Congenital Defects in Dogs:
Canine Leukocyte Adhesion Deficiency - CLAD
Congenital Portosystemic - Shunts in dogs
Defects of the Vertebral Column in Dogs
Return from Defects of the nervous system of dogs to Veterinary Articles Veterinary articles supplied by Dr S Strydom and published with kind permission of DIA Publishing - publishers of KUSA Dogs in Africa Magazine Dr Sunelle Strydom qualified as a veterinarian in 2004 at the Faculty of Veterinary Science, University of Pretoria. She has a passion for writing and the sharing of knowledge to promote animal health and welfare. She has written several articles for KUSA Dogs in Africa as well as for Vra vir Faffa on the Landbouweekblad website atwww.landbou.com References
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