Hydrocephalus in domestic animals

HYDROCEPHALUS IS swelling of the cranium due to an accumulation of fluid which may be in the ventricular system or between the brain and the dura. It affects all species of domestic animals. HC is either acquired or cogenital. Acquired type are generally caused by obvious brain insults such as viral infections and can occur at any age. Hypovitaminosis A leads to great reduction in the resorption of the fluid by the arachnoid villi. In viral infections there is failure of cell growth or necrosis of performed cells. The CNS lesions are produced by direct necrotising effect on virus on the developing neurons.

Congenital HC is characterised by young one with enlarged cranium at the time of birth. Such young animals do not survive more than 2-3 days after birth. In cattle it is seen sporadically and the exact reason for the occurrence is not yet determined. Generally two forms of HC is noticed in animals, internal and external HC. In internal HC there is increased accumulation of fluid in the ventricles which can occur at the foramen of monro or the aqueduct of sylvius. External HC is due to formation of more fluid or not being rapidly drained by the arachnoid villi. It is usually the result of rupture of the dorsal wall of the third ventricle. This thinning of the wall allows escape of the fluid in the subarachnoid space between the cerebral hemisphere and cerebellum.

Hydrocephalics which survive will show depression, uncoordinated gait, diminished learning ability, partial or complete failure of suckling, muscular fasciculations, drooped head and ears, head tremor, blindness, propriceptive deficits, ventrolateral strabismus, prominence of fore head, paretic in all limbs, tongue flaccidity or paralysis, retention of food in the cheek or lips, hyperflexia, psychomotor seizures and coma. In animals with unilateral leisons there is head tilt (towards the leiton side), ipsilateral mydriasis and contralateral menace deficits.

The diagnosis of HC is based on the presence of clinical signs and confirmation can be obtained by using various diagnostic techniques. These techniques are helpful only in small animals like dogs and cats. Computerised tomography, ultrasound, EEG and contrast ventriculograpy are the techniques used for confirming HC.

There is no satisfactory therapy for correction of HC. Treatment of congenital HC accompanied by severe cranial distortions is usually ineffective because of massive amount of brain damage present at birth. In acquired HC, various drugs are tried to correct the condition, but the results are questionable.

Use of glucocoticoids decreases CSF production and suppresses underlying inflammatory condition. It may be effective in dogs without significant cranial defects.

The diuretic, Acetazolamide, is shown to decrease CSF pressure. It would be of useful in patients with elevated intracranial pressure. Since it causes severe potassium loss, care must be taken not to intoxicate the patient. Hydrocephalics with seizures may require anticonvulsants. Phenoborbitol, 2-5mg/kg body weight is often adequate, with the dosage being adjusted to maintain a blood level between 15-40 migrocrams.

Surgical technique, shunting from the ventricular system to the peritoneal cavity or heat can be tried. Shunting has greater utility than medical management has not been proved. Satisfactory control of the clinical signs may be achieved in some cases, but in many there is no resolution of the profound neurological deficits, and the condition may be terminated.

N.Periasamy

Koppampatty, Trichy T.N.

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