Hydrocephalus in Dogs
Hydrocephalus, which means “water in the brains”, refers to the condition where excess cerebrospinal fluid builds up inside the skull, leading to increased pressure against the brain tissues. Prolonged pressure could lead to irreparable brain damage or death.
Pathophysiology of Hydrocephalus in Dogs
The brain and spinal cord are continuously immersed in cerebrospinal fluid (CSF), a clear fluid that protects and supplies nutrients to the central nervous system. Production of this fluid occurs in chambers of the brain called ventricles. After the CSF has circulated, the body will eventually reabsorb the fluid.
In patients with hydrocephalus, the abnormal accumulation of the CSF could be an overproduction or a drainage problem leading to the distention or dilation of the ventricular system. Congenital hydrocephalus is a condition that’s present at birth. And since puppies are born with soft craniums that are not fully closed yet, these can expand to accommodate the extra fluid. Skull bones eventually harden so adult dogs that have this condition will experience marked increase of pressure exerted against the brain because the cranium can’t expand.
Types of Hydrocephalus
Hydrocephalus in dogs can be categorized into two types: obstructive and compensatory. Both types can be congenital or acquired.
Obstructive hydrocephalus, also known as noncommunicating hydrocephalus, occurs when there’s a blockage in the ventricular system impeding the flow of the fluid. Conversely, communicating hydrocephalus occurs when CSF accumulation happens right after it exits the ventricular system; thus, its circulation in the ventricles remain open.
Congenital obstructive hydrocephalus may arise due to prenatal infection of the aqueduct of Sylvius, which subsequently leads to stenosis (narrowing). Acquired obstructive hydrocephalus may be brought about by an abscess, tumor, or inflammation secondary to hemorrhage or other brain diseases.
This type of hydrocephalus occurs when CSF fills up cranial spaces that normally would have been occupied by brain parenchyma that either failed to develop or are damaged. For instance, in cases of brain atrophy due to old age, CSF would fill up the spaces of those damaged neurons.
Causes of Hydrocephalus
Several contributing factors could lead to hydrocephalus. The most common ones include:
- Genetics. In particular, brachycephalic breeds like Chihuahua, Pugs, Yorkshire Terriers, and Pomeranians are more likely to develop the congenital form of this condition
- Prenatal infection
- Exposure to drugs that affects the fetal development in the uterus
- Brain injury
- Brain hemorrhage arising from difficult labor
- Brain tumor
- Intracranial inflammatory diseases
Signs and Symptoms
For congenital hydrocephalus, clinical signs of the condition become more evident at 8-12 weeks of age. The skull would appear rounded with an open fontanelle at the top of the puppy’s head. Aside from this physical abnormality, the puppy may also exhibit the setting sun sign, an ocular abnormality where the iris is positioned low, much like the sun when it dips into the horizon. Neurologic signs like seizures, mental dullness, blindness, learning disability, and walking in circles may also be present.
In acquired hydrocephalus, there may be no evident symptoms of the condition. But in most cases, symptoms to look out for are abnormal gait, nausea vomiting, double or blurred vision, difficulty in balancing, lethargy, irritability, slow cognition, changes in personality, and urinary incontinence. In severe cases, hydrocephalus could lead to coma or death.
When taking the dog’s medical history and performing a physical exam, the veterinarian will take note of the clinical signs to determine the severity of hydrocephalus and other underlying conditions that may precipitate this illness. Mental development, neurologic, and physical signs are the main focus when making an initial diagnosis. But to arrive at a definitive diagnosis, the veterinarian may request for further diagnostic tests.
Standard Diagnostic Tests
Complete blood count, urinalysis, and biochemical analysis are the standard diagnostic procedures that can help the veterinarian pinpoint other conditions that may have the same clinical signs with hydrocephalus. These tests also help determine the general well-being of the animal so the vet can make an informed decision if the need to have the pet undergo surgery ever arises.
Imaging procedures like radiography, ultrasound, CT scan, and MRI are needed to truly confirm hydrocephalus. While radiography is the least expensive of the procedures, MRI is the imaging technique of choice by veterinarians when it comes to hydrocephalus. MRI results provide a detailed image of the brain, including the size of the ventricles and if inflammation in any part of the brain is present. Once the diagnosis is confirmed and the underlying condition of acquired hydrocephalus is determined, then pet owners and the family veterinarian can pursue appropriate treatments.
Other Diagnostic Tests
In some cases, the veterinarian may also request for a spinal tap, a procedure wherein a sample of spinal fluid is obtained for analysis. This is used to estimate CSF pressure as well as determine if a shunt is the best treatment to resolve hydrocephalus. The dog will have to be under anesthesia for this procedure. Additionally, an electroencephalogram may also be necessary to measure brain activity.
Treatment of hydrocephalus largely depends on the severity of symptoms. And if there’s an underlying condition that caused hydrocephalus in dogs, the treatment approach must focus on resolving that as well.
Dogs with mild symptoms may be treated on an outpatient basis using medications. Medications are prescribed mainly to relieve fluid pressure and alleviate the symptoms. Common medications prescribed includes:
Diuretics. These drugs can be used to increase the amount of water expelled by the body, thus providing temporary relief to CSF pressure in the brain. However, this must be administered under close supervision since the dog may suffer electrolyte imbalance as a side effect of this type of drug.
Glucocorticoids. Drugs like prednisone and dexamethasone may be used to reduce the production of CSF and treat inflammation in the brain. However, these drugs can’t be used in the long term as these may cause serious side effects.
Other drugs. Medications that are used to relieve other symptoms include anticonvulsants to control seizures and omeprazole to decrease CSF production as well as minimize the side effects of other drugs to the gastrointestinal tract.
To resolve the condition permanently, a shunt may have to be surgically placed to channel the fluid away from the brain and into the abdominal cavity where they’re mostly reabsorbed by the dog’s body. This is mostly prescribed for severe congenital hydrocephalus. However, surgery can be very expensive and complications like infection, migration or mechanical failure of the shunt, and obstruction may arise. As the puppy develops, the shunt may have to be replaced or refitted.
Outlook and prognosis for dogs with hydrocephalus depend on the type, cause, and severity of the condition. The prognosis for severe congenital hydrocephalus as well as those with an acquired type due to a tumor is guarded. If not surgically treated, dogs with this condition may have to be euthanized. Approximately 70% of dogs that underwent surgery show improvement in clinical signs.
On the upside, dogs with mild symptoms of this condition have a good prognosis. And they may only need medical intervention to keep the symptoms under control.
Scheduling a consultation with the veterinarian at the onset of symptoms helps obtain a better prognosis for the dog. When proper treatment is pursued while the symptoms are mild, the dog may recover completely without any long-term damage to the brain.