Your pup has four ventricles in his brain. When the system doesn't work properly, a dog can develop a condition commonly called water on the brain, or hydrocephalus.
When CSF collects in your pup's brain it's because of a drainage problem, referred to as obstructive hydrocephalus, or there's too much fluid being produced, known as compensatory hydrocephalus. It's a condition your little guy can be born with, or it can develop later in life. Though any dog can have water on the brain, toy breeds and brachycephalic -- short-faced -- breeds are more prone to the condition.
Two Paths to Hydrocephalus
A dog with congenital hydrocephalus wasn't born with water on the brain; instead, he was born with a condition that led to water on the brain. For one of these pups, parts of the brain join together, narrowing the passageways carrying the CSF. Prenatal infection and exposure to certain drugs in utero, as well as genetics and brain hemorrhages in newborn pups, are some reasons a puppy may have hydrocephalus. Brain tumor, head injury, inflammation of the brain or tissue around the brain and spinal cord may also contribute to water on the brain, referred to as acquired hydrocephalus.
Paying Attention to Clues
In most cases, puppies begin to show signs of hydrocephalus between 2 and 3 months of age, though not every dog shows symptoms. A puppy with water on the brain often has a very round-looking skull and an open soft spot on the top of his head. Other signs of hydrocephalus in puppies and dogs include lethargy or sleepiness, housebreaking accidents, blindness, abnormal gain, eyes directed downward -- called the setting sun sign -- lack of coordination and difficulty learning.
Working Toward Treatment
The more information you can provide to the vet abut your pup the better, including information about his birth and parents. In addition to blood work and urinalysis to rule out other conditions, diagnostic imaging will confirm diagnosis. Radiographs are useful but are not conclusive for diagnosis. CT scans -- computed tomography -- and magnetic resonance imaging provide the vet the most valuable images for diagnosis. If the symptoms are severe, or the dog needs surgery, he'll be hospitalized for treatment. Medication such as diuretics and corticosteroids can help relieve fluid pressure and swelling in the brain. In some instances, a shunt is necessary to drain excess fluid from the brain into the abdominal cavity. The prognosis depends on what's causing the hydrocephalus and how severe it is.