Dog Health by LowchensAustralia.com

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 the following tests: 

• Neurological assessment 
• Laboratory work assessing kidney and liver function
• Skull radiographs
• Computed tomography or magnetic resonance imaging
• Ultrasound of the brain if there is an open fontanel present
• Spinal tap (rarely performed)
• Electroencephalogram (EEG)

Treatment

The goal of treatment is to minimize or prevent brain damage by improving CSF flow. Treatment depends on the severity of the clinical signs and may include one or more of the following: 

Medical treatment consisting of drugs that either decrease the production of CSF or increase CSF absorption

Surgical treatment of hydrocephalus that includes direct removal of the obstruction or shunting of CSF to an area outside of the brain

Prevention of trauma such as falling or rapid changes in pressure 

Follow-up examinations throughout the animal's life to evaluate any progressive brain damage and to adjust treatments 

Prognosis

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.

Information In-depth

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) to 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.

Causes

• Canine distemper
• Parvovirus
• Parainfluenza virus
• Bacterial meningitis
• Aberrant parasitic migration
• Fungal encephalitis
• Ependymoma
• Choroid plexus papilloma
• Meningioma
• Pharyngioma
• Epidermoid & dermoid cysts

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

• Chihuahua
• Maltese
• Yorkshire terriers
• English bulldogs
• American bulldogs
• Lhasa Apso
• Pomeranian
• Toy poodles

Veterinary Care In-depth

Veterinary care should include diagnostic tests and subsequent treatment recommendations. 

Diagnosis In-depth

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. 

Laboratory work assessing your pet’s general health and the presence of an underlying disease that may be causing the hydrocephalus. Recommended tests may include:

• A complete blood count (CBC or hemogram)

• Serum biochemistry tests to evaluate blood glucose, electrolytes and protein

• Urinalysis

• Fecal analysis

• Skull radiographs to evaluate your pet’s skull for signs consistent with hydrocephalus
  Ultrasound, a non-invasive method that allows observation of the brain and ventricular system if there is an open fontanel present

• Computed tomography or magnetic resonance imaging, non-invasive methods that gives your veterinarian the ability to look at your pet’s brain and degree of hydrocephalus. At times the imaging can determine specific causes of hydrocephalus in the case of tumors and fluid obstructions. Your pet would need to be anesthetized for these procedures. 

• A spinal tap to obtain CSF for examination. (rarely performed). This test also requires anesthesia.

• An electroencephalogram (EEG) is an electrical recording of the brain’s activity. This test requires a specialized piece of equipment and training that may be available only at a few specialty practices.

Treatment In-depth

The goal of treatment is to minimize or prevent brain damage by improving CSF flow. Treatment depends on the severity of the clinical signs and may include one or more of the following: 

• Medical treatment consisting of drugs that either decrease the production of CSF or increase CSF absorption

• Surgical treatment of hydrocephalus to include direct removal of the obstruction or shunting of CSF to an area outside of the brain. Surgical removal of the obstruction may be indicated with tumors or malformations. 

• Shunt surgery, which is the surgical placement of a tube into the dilated ventricles. This tube is then tunneled under the skin to an area outside of the brain such as the right atrium of the heart or to the abdominal cavity. 

• Prevention of trauma such as falling or rapid changes in pressure 

• Antibiotic therapy to treat signs of infection when surgery is performed

• Removal or revision of shunts 

• Follow-up examinations throughout the animal's life to evaluate any progressive brain damage and to adjust treatments.

Prognosis and Home Care

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.

Call your veterinarian promptly if your pet shows symptoms of hydrocephalus. Contact an emergency clinic or your veterinarian if emergency symptoms occur including lethargy, fever, increased somnolence, stiff/painful neck, seizures or deteriorating level of consciousness.

Protect the head of your pet from injury by handling him carefully and preventing falls. Promptly treating infections associated with hydrocephalus may reduce the risk of developing the disorder.


By: Dr. John McDonnell
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