The most common form of hydrocephalus is congenital hydrocephalus. In congenital hydrocephalus, the excess fluid accumulates before or soon after birth. We are not sure why this happens in all cases, but possibilities include an inherited malformation of the fluid pathway or infection or injury around the time of birth. Less commonly hydrocephalus occurs in adult dogs, usually due to a tumor or infection in the brain that obstructs the CSF pathways. Congenital hydrocephalus occurs in young puppies.
Sporadic cases can occur in any breed, but it is most common in small and toy breeds.
If hydrocephalus occurs in a puppy there is usually an abnormally large, dome shaped head. If hydrocephalus occurs after the skull has stopped growing, the head will not enlarge. Hydrocephalus can cause a variety of neurologic signs, including seizures , incoordination, abnormal behavior, a tendency to walk in circles, and blindness. These signs may wax and wane or become worse over time. Diagnosis is based on the signs in conjunction with techniques to image the brain.