Hydrocephalus is an abnormally large accumulation of cerebrospinal fluid within the cavities of the brain (known as the 'ventricular system'). Most commonly this is a congenital defect (i.e. present at birth). Its cause is a defect in the midbrain impairing the normal flow of fluid within the brain, which brings oxygen and nutrients. Thus it may result in distention of the size of the ventricles, leading to pressure on, and potential damage to, the brain tissue itself.
What are the clinical signs?
Clinically affected inpiduals may suffer learning difficulties, epileptic seizures, and visual impairment. Animals often have a dome-shaped head, and palpably open fontanelles (the soft membranous gaps between the cranial bones of the skull of a newborn human or animal); they may also have a noticeable eye deviation. (Occasionally, dogs with hydrocephalus can be initially or permanently asymptomatic.)
Are specific breeds predisposed?
Hydrocephalus is common in small breeds, the toys and brachycephalic breeds such as:
- Chihuahua
- Yorkshire Terrier
- Boston Terrier
- Miniature Pinscher
- Bulldog
How is a diagnosis made?
Several diagnostic procedures are possible such as ultrasound (if the fontanelles are open), CT scan or magnetic resonance imaging (MRI). The latter remains the best method to visualize and quantify the dilated ventricles, and also ensure that there are no other concomitant anomalies.
What is the treatment?
There is a treatment using medication designed to reduce the production of cerebrospinal fluid and limit the surrounding brain-swelling. Also, a surgical treatment is available in which a bypass, or shunt, is installed, to allow the superfluous cerebrospinal fluid to drain into the abdominal cavity, from where it is harmlessly absorbed into the body.
What is the prognosis?
The prognosis depends on the severity of hydrocephalus, significance of relevant clinical signs as well as on the dog's age and general health.
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