Hydrocephalus and Ventriculoperitoneal Shunt Placement

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Filed Under: Internal Medicine

Hydrocephalus and Ventriculoperitoneal Shunt Placement

Hydrocephalus, commonly called “water on the brain”, is a condition in which cerebrospinal fluid (CSF) builds up in the ventricles of the brain (cavities where it is produced) causing compression.  This build up may be obstructive, meaning something is blocking or preventing CSF from draining normally, or compensatory, meaning CSF is filling empty spaces (such as areas of the brain that did not develop normally).  Hydrocephalus may be either congenital, meaning it was present at birth, or acquired, meaning it developed later for some other reason (such as trauma, inflammation, hemorrhage, tumor, or other).

SF is continuously produced in the ventricles of the brain and serves to cushion and protect the brain and spinal cord.  CSF drains through the foramen magnum, the large opening at the base of the skull, follows along the spinal cord, and is eventually absorbed by the body.  The skull is a rigid compartment with no opportunity for expansion.  When CSF is blocked from normal drainage from the skull, a buildup of fluid occurs and structures of the brain may be compressed and damaged.

A frequent sign of hydrocephalus is a large domed or “apple” shaped head. 


Chihuahuas are one of the breeds that may commonly have congenital hydrocephalus which often includes an open fontanelle (spot on the top of the head where the skull bones have not closed and is soft).  Other breeds include many toy and brachycephalic breeds such as: bulldogs, Maltese, Yorkshire Terriers, Pomeranians, Toy Poodles, Lhasa Apsos, Cairn Terriers, Boston Terriers, Pugs, and Pekingese, although other breeds and cats may also have hydrocephalus. Any Pet may develop acquired hydrocephalus.

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Symptoms of hydrocephalus may include: mental dullness, disorientation, dementia, lethargy or excessive sleepiness, lack of coordination or ataxia, change of gait, behavioral changes and compulsive behaviors (aggression, circling, tail chasing, etc.), inability to learn, regression of learned behaviors (house soiling, commands), head pressing, seizures, and others.

Diagnostic imaging, typically an MRI, is needed to confirm a diagnosis of hydrocephalus. The black area inside the skull in these images is an excess of CSF, denoting hydrocephalus.


Hydrocephalus may be treated with medical therapy using medications to decrease CSF production and encourage elimination of fluids from the body (such as omeprazole, corticosteroids, and diuretics) or with surgery and the placement of a ventriculoperitoneal shunt.

The ventriculoperitoneal shunt is a tiny diameter tube. During surgery, it is inserted into the brain where the CSF is and from there, it is fed underneath the skin down to the abdominal cavity, where the other end of the tube stops. In the middle, there is a one way valve that very slowly and continuously drains CSF into the abdomen. From the abdomen, CSF is absorbed back into the body. This shunt is meant to be permanent, so that excess CSF does not build up at any time in the future.

The two biggest complications we worry about with a shunt are (1) infection, and (2) obstruction. The biggest risk of infection is immediately after the surgery until the skin heals. Surgery is performed under aseptic / sterile conditions, and antibiotics are prescribed for the first week after surgery, to decrease the risk of infection. Obstruction occurs most often if the CSF fluid becomes thicker than normal, which is uncommon. If the shunt becomes infected or obstructed, we may need to replace it or remove it in the future.

Prognosis for hydrocephalus is widely variable and depends on whether it is congenital or acquired, how severe the Pet’s symptoms are, and how the Pet responds to treatment.