Treatment of hydrocephalus may be medical or surgical. Medical treatment involves the use of glucocorticoids, such as prednisone, and diuretics, such as furosemide and acetazolamide, which reduce CSF production. Medical therapy usually does not provide long-term resolution of clinical signs unless a specific cause can be identified and resolved with treatment.

Medical Treatment

Medical treatment of hydrocephalus decreases CSF volume and production through the use of diuretics and glucocorticoids. The long-term use of any diuretic can cause electrolyte depletion and its use must be careful. Electrolyte loss is accelerated when diuretics are used in combination with glucocorticoids.

Furosemide inhibits the sodium-potassium co-transport system that decreases CSF production in extracellular fluid. Furosemide should be administered at a dosage of 0.5 to 4 mg/kg PO q12–24h and then tapered to the lowest effective dose. In cases where a quick decompensation is needed, mannitol, an osmotic diuretic, is used. A dose of 1g/kg should be administered intravenously over 15 to 20 minutes and may be repeated 3 times over 24 to 48 hours when needed. Acetazolamide, a carbonic anhydrase inhibitor, is thought to reduce CSF pressure by decreasing CSF production. However, its effectiveness in treating hydrocephalus is inconsistent. A dose of 10 mg/kg PO q6–8h has been recommended.

Glucocorticoids are used to decrease CSF production, thereby limiting ICP and further neurological injury. Prednisolone at 0.25–0.5 mg/kg is given orally twice daily. The dose is gradually reduced at weekly intervals to 0.1 mg/kg every other day. This dose is continued for at least 1 month. Then, the medication is discontinued if possible. Alternatively, dexamethasone may be given orally at 0.25 mg/kg every 6 to 8 hours. The dose can be gradually reduced over 2–4 weeks. Some animals can be adequately managed with long-term glucocorticoid administration at low doses.

Surgical Treatment

Surgical treatment may be recommended for those animals that do not improve within 2 weeks with medical treatment or if deterioration occurs during corticosteroid therapy. The goal of surgical intervention is to provide drainage of CSF from the brain to another site for absorption. The most common surgical procedure in veterinary patients is the implantation of a ventriculoperitoneal shunt (VPS), because it is easiest to install and is frequently used in human neurosurgery. In this technique, a fenestrated catheter is inserted into the ventricular system (right or left lateral ventricle), and then, a valve that controls gravity-induced hydrostatic pressure and a distal catheter are fitted together. The distal catheter is guided through the subcutaneous tissues until reaching the abdominal cavity. A less common alternative shunt is the ventriculoatrial shunt, in which the distal catheter is inserted into the jugular vein until it reaches the right atrium.

Choosing the Suitable Valve System

Several devices have been described in the literature for performing a VPS in dogs. However, a high number of these devices can become obstructed with proteinaceous build-up, leading to drainage reduction and return of intracranial hypertension. There are low (30–50mm H₂O), medium (60–80 mm H₂O), and high-pressure (90–110 mm H₂O) valves for maintaining ventricular pressures within preset ranges. The normal ICP in dogs is between 8 and 12 mm Hg (108.7–163.1 mm H₂O) and CSF production occurs at a mean rate of 2.82 ml of CSF/h.

In order to choose the suitable valve during the surgery, we recommend that ICP be measured using a parenchymal micro sensor linked with an ICP monitor. In despite of its high cost, this device can help the surgeon to choose the valve according to the measured ICP. In cases where this device is not available, we recommend the use of high-pressure valve (90–110 mm H₂O) because its valve works nearly at the normal ICP of dogs and may prevent over drainage.

Contraindications

Contraindications to implanting a ventriculoperitoneal shunt include evidence of CSF infection, an elevated CSF protein concentration, a high erythrocyte count in the CSF, or peritoneal inflammation. It is also important to resolve other systemic infections (e.g., urinary tract and skin infections) before scheduling ventriculoperitoneal shunting surgery.

Prognosis

The prognosis for dogs and cats with congenital hydrocephalus is variable, but is generally guarded. Medical therapy may be effective in some patients, whereas others require surgical shunting procedures for the long-term control of clinical signs. The prognosis for sustained clinical improvement in neurologic status after surgical shunting procedures varies in the literature from 50 to 90% for dogs. In ours experience, the success rate is approximately 70%.

Complications

Over drainage is a common complication and may occur in catheters without a valve system. The absence of a control valve immediately after the proximal catheter, leads to an excessive and abrupt reduction of CSF, causing headache, vomiting, subdural hematoma, proximal obstruction, and changes in vision.

Complications associated with shunt placement such as infection and obstruction are similar in veterinary and human medicine. Evidence of erythema along the shunt tract or insertion site can indicate infection.

References

1.  Coates JR, Axlund TW, Dewey CW. Hydrocephalus in dogs and cats. Compend Cont Educ. 2006;28:136–147.

2.  Przyborowska P et al. Hydrocephalus in dogs: a review. Veterinarni Medicina. 2013;58(2):73–80.

3.  Filgueiras RR et al. Long-term evaluation of a new ventriculoperitoneal shunt valve system in a dog. J Vet Emerg Crit Care. 2009;19(60):623–628.

4.  Dewey CW, Da Costa RC, eds. Practical Guide to Canine And Feline Neurology. 3rd ed. Ames, IA: Willey Blackwell; 2016.