Hydrocephalus

puppies

Hydrocephalus (a.k.a., water on the brain) is a condition of the brain where there is an imbalance in the production and the absorption of cerebral spinal fluid (CSF) in the ventricle system. CSF is the clear, water-like fluid that surrounds the brain and the spinal cord. It also cushions these two organs. An imbalance in the production / secretion and / or the absorption of the CSF causes this fluid to accumulate in the ventricles. The ventricles of the brain become dilated and this increase in volume causes the surrounding brain tissue to become compressed against the skull. If this occurs before the skull sutures are fused (fixed and closed), it will cause the head to swell. The sutures fuse at around 12 years of age. Below that age, when the sutures are partially fused, they can become diastatic or opened.

Causes for Hydrocephalus

The purpose of CSF is to deliver vital nutrients to the brain and to rid the brain of waste products. In the perfect world, CSF will flow through its typical narrow passageways and exit the brain through a reservoir at the base of the brain, called the cistern. If a blockage occurs in any of the passageways (including the ventricles), the CSF will back up and cause an excess of fluid in the brain. The excess fluid leads to increase pressure under the skull. With that increased pressure the brain tissues will move to the area of least resistance which ultimately will be the base of the skull. This will lead to brain herniation, which is a medical, life threatening emergency.

Signs/Symptoms

Early Infancy: rapid head growth, bulging fontanel (soft spot on the top of head), separating sutures, dilated scalp veins, and Macewen sign which is a cracked-pot sound on percussion.

Later Infancy: bulging fontanels, forehead enlargement (known as bossing), depressed eyes / setting sun eyes, pupils sluggish with unequal response to light.

Infancy in general: fussiness, lethargy (sluggish and inactive), change in level of consciousness, vomiting, spasticity in the legs, difficulty sucking and feeding, and high pitched cry.

Childhood: headache, vomiting, irritability, lethargy, confusion, loss of coordination, cross-eyed (strabismus) and inability to concentrate.

Diagnostic Evaluation

In addition to the subjective findings seen by the physician, the gold standard for diagnosing hydrocephalus is a CT (computed tomography) scan, also known as a “cat scan” or an MRI (magnetic resonance imaging).

Treatment

Treatment for hydrocephalus is geared towards relieving the condition. This can be done by surgical intervention, which involves removal of the obstruction, as in the case of a tumor. Or it can be accomplished by placing a device known as a shunt (ventriculoperitoneal or VP shunt), which will drain the excess fluid. This shunt system consists of a catheter placed in the ventricle of the brain, a flush pump, a unidirectional flow valve, and a distal catheter. The distal catheter usually terminates in the peritoneum (the area that houses the abdominal organs, i.e., the stomach, liver, etc.).

Complications/Prognosis

The main complications of the VP shunts are malfunction and infection. All shunts are capable of having some mechanical issues such as catheter kinking, plugging, separation or migration of the tubing. If this occurs, a revision by the doctor may be warranted. Infections are treated with antibiotics. Reoccurring infections may require removal of the shunt and placement of a new shunt. When hydrocephalus is treated medically and surgically, there is an 80% survival rate, with the highest incidence of mortality occurring within the first year of obtaining diagnosis and treatment.