Water on the brain, formally known as hydrocephalus, occurs when cerebrospinal fluid builds up in that organ. While hydrocephalus can develop in older dogs because of trauma or a disease blocking cerebrospinal fluid drainage, in puppies it's a congenital condition. Severely afflicted puppies often die early on. Puppies with less severe cases might not be diagnosed until they are several months old.
A dog's brain includes four fluid-filled areas called ventricles. Normally cerebrospinal fluid flows into these spaces, eventually entering the bloodstream via "cisterns" at the brain's base. If cerebrospinal fluid collects in the ventricles, hydrocephalus results.
Although any puppy can be born with hydrocephalus, certain breeds are genetically predisposed to the condition. These include the Chihuahua, Yorkshire terrier, bulldog, Lhasa apso, Maltese, Pomeranian, toy poodle, cairn terrier, Manchester terrier, Pekingese, shih tzu and Boston terrier. Dogs with hydrocephalus should not be bred.
Symptoms generally appear by the time a pup is 3 months old. Puppies born with hydrocephalus often don't grow as fast as their litter mates, generally remaining smaller. Their skulls might appear domed—a condition that becomes worse as fluid collects and time passes. As they grow, such puppies might appear mentally backward, slow to catch on to basic training concepts such as housebreaking. Other signs include head-pressing, or pushing the head into a corner; eyes directed downward or sideways; vision issues; and seizures. Some affected puppies don't show any symptoms. Your vet diagnoses the condition based on a physical examination and through ultrasound, computed tomography or magnetic resonance imaging scans of the puppy's brain.
Mild hydrocephalus might respond to medication, specifically steroids that reduce the amount of cerebrospinal fluid. Diuretics, medications that rid the body of fluids through increased urination, might also be used. If your puppy suffers from seizures, your vet might prescribe phenobarbital for treatment. Often dogs with mild hydrocephalus don't get worse after the age of 2, although they might always remain a little slow.
Installing a shunt to drain away cerebrospinal fluid can aid more seriously affected puppies. Your vet can recommend a veterinary neurologist to perform this delicate surgery. The shunt, a tube placed in a ventricle, siphons off the fluid into the abdomen or another area that can handle the excess fluid. Since the puppy continues to grow, shunts might need replacement to match the dog's size. According to a German study appearing in the American Veterinary Medical Association Journal, 22 percent of animals in the study developed postoperative complications following shunt installation, but 72 percent clinically improved after shunt placement.