Hydrocephalus in Dogs

Hydrocephalus may be seen in young animals (less than 18-months-old) or older animals (greater than six-years-old). 

Hydrocephalus (water-head, term derived from Greek) is the malfunction of drainage system of the brain responsible for evacuating the cerebrospinal fluid from the brain into the circulatory system.  In hydrocephalus condition the fluid builds up in the two large interconnecting chambers, and the brain and skull become enlarged because of the accumulation of the fluid.  Hydrocephalus may be an acquired or congenital (present at birth) condition and may be caused by birth defects of the brain's drainage system, head injuries, tumours, parasitic or other infections. In young dogs, the presence of a dome-shaped head and/or non-closing, or persistent fontanel (also called fontanella) may indicate the development of hydrocephalus.  Fontanel is a small gap between the incompletely formed cranial bones.  Several such spots are usually present at birth and in most cases close usually by 3 or 4 months of age.

The symptoms of hydrocephalus include depression, severe loss of movement coordination, eye abnormalities, seizures, vision problems, and skull enlargement. Young affected puppies often show un-thriftiness - slow growth as compared to their littermates.  When older animals are affected by hydrocephalus, outward signs are not as evident since the bones of the skull are already fused.  Symptoms of hydrocephalus vary with the cause, the age at presentation, the brain tissue being compromised, and the degree of tissue damage. 

What to watch for:  Altered mental status, Crying out, Hyperexcitability, Extreme dullness, Coma, Seizures, Visual or auditory impairment, Spastic or clumsy walking, Circling, Head pressing, Head tilt, Abnormal eye movements, Diagnosis

Diagnostic tests are needed to identify hydrocephalus and differentiate it from other diseases that may cause similar signs.  In addition to obtaining a complete medical history and performing a thorough general physical examination, your veterinarian will likely perform or recommend various tests.  

Untreated severe hydrocephalus has a poor prognosis and usually results in death. Although the efficacy of therapy cannot be assessed without attempting treatment, the severity of clinical signs correlates with the success of treatment. Animals with symptoms that are difficult to manage are poor candidates for medical or surgical treatment.  Some animals with congenital hydrocephalus have an immediate response to medical or surgical treatment and can be stable over a long period of time.

Hydrocephalus is a neurological disease in which there is excessive accumulation of cerebrospinal fluid (CSF) within the ventricular system of the brain. The fluid in the brain (CSF) is normally formed in the brain.  It bathes, protects, and circulates through the ventricular system within the brain and the coverings and is then absorbed into the circulatory system.  The production of CSF has an active and passive component; absorption is only a passive process.  When the absorption of CSF is blocked or excessive fluid is produced, the volume of CSF increases.  The increased CSF volume puts pressure on the brain, forcing it against the skull, damaging or destroying the tissues.  Symptoms of excess CSF volume vary with the cause, the age at presentation, the brain tissue being compromised, and the degree of tissue damage. In young animals, CSF can accumulate in the brain causing the fontanel (soft spot) bulge.  The bones of the skull are soft and can be enlarged due to the increased volume and pressure leading to a dome shaped cranium. The eye position within in the eye socket may be abnormally deviated where the white portion of the eye (sclera) is visible in both eyes towards the nose.

The most common cause of hydrocephalus in young animals is congenital defect. Toy breeds have the highest incidence. Some commonly affected breeds include the Lhasa Apso.

Diagnostic tests are needed to identify hydrocephalus and differentiate it from other diseases that may cause similar signs. In addition to obtaining a complete medical history and performing a thorough general physical examination, your veterinarian will likely perform or recommend the following tests: 

Neurological assessment. Because of excessive CSF that may be pressing on the brain, your veterinarian will perform a complete neurologic examination assessing your pet's mental status, level of consciousness, cranial nerve examination, gait assessment, postural reactions, spinal nerve reflexes and sensory examination. 

Untreated hydrocephalus has a poor prognosis and usually results in death.  Although the efficacy of therapy cannot be assessed without attempting treatment, the severity of clinical signs correlate with the success of treatment.  Animals with intractable symptoms are poor candidates for medical or surgical treatment. 

Some animals with congenital hydrocephalus have an immediate response to medical or surgical treatment and can be stable over a long period of time.