Hydrocephalus is a condition characterized by an abnormal accumulation of cephalorachid fluid (LCR) inside the brain. Usually, hydrocephalus is congenital. Occasionally, the onset of this condition may occur following head injury, brain hemorrhage, vitamin A deficiency, brain neoplasms or exposure to drugs, chemicals, bacteria, viruses or other toxins.
Normally, the volume of the cephalorachid fluid is carefully regulated by complex neurological mechanisms. This liquid lubricates the brain by flowing through a system of small chambers called ventricles. When an excessive amount of cephalorachid fluid is produced or when the brain does not regulate this quantity correctly, the liquid accumulates in the aforementioned ventricles by exerting pressure on the brain.
The canine hydrocephalus is almost always congenital (present at birth). As a result, this condition is most commonly diagnosed in puppies. Sometimes, hydrocephalus can also occur in adult animals, but this is an uncommon occurrence in domestic dogs.
Different classification schemes are used in veterinary medicine to characterize hydrocephalus. One distinguishes between two general types of the disorder: communicating hydrocephalus and non-communicating hydrocephalus.
In the case of communicating hydrocephalus, the animal’s brain is unable to absorb a normal amount of cephalorachid fluid from the cerebral ventricular system. The cerebral ventricles are chambers located inside the brain through which the cephalorachid fluid flows.
In dogs with communicating hydrocephalus, there is no physical obstruction in the free movement of cephalorachid fluid through and between the ventricles. On the other hand, there is an overproduction of this liquid (although it is an event not particularly common in dogs) or an anomaly or damage to the brain of the dog which prevents the correct absorption of the cephalorachid fluid.
The communicating hydrocephalus is usually congenital. However, it can also be acquired following trauma, inflammation, cerebral hemorrhage, infection, food deficiency of vitamin A or brain neoplasms. In another classification scheme, this is referred to as compensatory hydrocephalus, since the excess of cephalorachid fluid fills the ventricular spaces, which may or may not be affected by dilation due to the damage occurred, the development or another pathological process.
Unlike the communicating hydrocephalus, the non-communicating hydrocephalus involves an obstruction affecting the normal flow of cephalorachid fluid through the cerebral ventricular system. It is usually a congenital physical obstruction. It can be caused by the exposure of the mother during pregnancy to drugs, chemicals or other toxins that cause birth defects in puppies. These substances are called “teratogenes”. Even some infections by bacteria, viruses (in particular the flu virus) or by other microorganisms, if contracted during pregnancy, can lead to the onset of congenital hydrocephalus in one or more puppies of the same litter. Although not so common, obstructive hydrocephalus can also be acquired secondary to traumatic injuries, cerebral hemorrhage, abscesses and / or cerebral neoplasms.
Regardless of the type (congenital or acquired), the effects of hydrocephalus are largely the same. The symptoms related to this condition are mainly due to the physical compression of the blood vessels in the brain (cerebral vasculature) caused by excessive intracranial pressure resulting from the abnormal accumulation of cephalorachid fluid in the ventricles. This pressure compromises blood flow and reduces the supply of oxygen and other nutrients to brain tissues. The effects of hydrocephalus are also attributable to physical damage to nerve cells, called neurons. This occurs as a result of dilation of the fluid-filled ventricles that compress neurons against other structures and against the bones of the skull.
Dog owners with hydrocephalus (whether congenital or acquired) may not notice any signs of the disease, especially in toy and miniature breeds. When symptoms are present, the owner can observe one or more of the following:
- Domed skull (high head, rounded)
- Dulling of the sensory
- Lack of coordination (ataxia)
- Excessive tiredness and sleepiness
- Changes in mental activity
- Behavioral changes
- Compulsive behaviors, such as abnormal vocalization, circling (continuous going round and round), tail-chasing (tail chasing)
- Head pressing (compulsive act that consists in pressing the head against a wall or an object for no apparent reason)
- Changes in gait or gait
- Changes in posture
- Inability to learn normally; lack or loss of the apparent ability to behave based on previous training
- Abnormal ocular positioning (eyeballs rotated downward and outward, ventrolateral deviation of the orbits, ventrolateral strabismus)
- Visual changes (partial / complete blindness)
The nature and severity of the dog’s symptoms may not necessarily correspond to the degree of dilation of the cerebral ventricles caused by the increase in volume of the cephalorachid fluid. In other words, a dog that has a slight buildup of fluid in the brain can exhibit serious clinical signs, while a dog with a significant buildup of fluid can only exhibit mild symptoms or no signs of the condition.
Dogs most at risk
Congenital hydrocephalus is quite common in some toy and brachycephalic breeds, especially in Chihuahuas whose domed skulls are considered a distinctive trait, which however predisposes the breed to the development of hydrocephalus. Barboni Toy, Lhasa Apso, Carlino, Volpino di Pomerania, Pekingese, Maltese, Shih-Tzu, Bulldog, Boston Terrier, Yorkshire Terrier, Manchester Terrier and Cairn Terrier are also predisposed to the development of congenital hydrocephalus.
Other factors that may be associated with hydrocephalus have been reported, such as small size of puppies at birth, stressful delivery (dystocia, or difficult birth) and short pregnancies.
Acquired hydrocephalus can arise in any dog breed. There is no known predisposition about gender. Congenital hydrocephalus is generally noticed at 1 year of age, while acquired hydrocephalus can arise in dogs of any age.
Hydrocephalus itself is not particularly difficult to diagnose, although it may be necessary to go to a specialized veterinary clinic equipped with appropriate diagnostic tools.
Typically, the veterinarian, after collecting the medical history from the owner’s direct voice and after performing a routine physical examination, will perform a thorough neurological examination. Most veterinarians will take urine and blood samples as part of the initial data collection. However, if hydrocephalus is the only problem for the dog and if it is not caused by an infection or another systemic disease, the results of these tests will usually be normal. Cranial radiographs may be recommended. These may reflect the anatomical changes associated with hydrocephalus.
To reach a definitive diagnosis of hydrocephalus, it is often necessary to carry out advanced tests, including ultrasound, computed tomography (CT) and / or magnetic resonance imaging (MRI) of the brain and skull. Another valuable aid for hydrocephalus diagnostics is electrocephalography (the graphic recording of electrical phenomena that take place in the brain), in particular for the diagnosis of congenital hydrocephalus.
The veterinarian may recommend the evaluation of cephalorachid fluid, depending on the circumstances of the specific case. The analysis of the cephalorachid fluid requires general anesthesia. The specimen is typically collected in the back of the neck, where the spine meets the skull. The veterinarian will proceed with extreme caution to insert a sterile spinal needle perpendicular to the dog’s skin, until the instrument enters what is called “subarachnoid space”. At this point, the cephalorachid liquid will flow freely through the needle into a special collection tube, to be subjected to a veterinary pathology laboratory. The sampling must be carried out with extreme caution, in consideration of the high intracranial pressure that usually accompanies the condition. The insertion of a spinal needle into the subarachnoid space creates a passage, through which the accumulated cephalorachid fluid has a way to escape. This can cause the brain to escape from where it is normally contained through this opening, which can be fatal.
Dogs with hydrocephalus that have a rapid onset of neurological signs need immediate veterinary intervention. This must be considered a real medical emergency. It is good to pay attention so that the dog with hydrocephalus is not overhydrated, by means of aggressive intravenous or subcutaneous fluid therapy, to avoid accelerating the increase in intracranial pressure.
Theoretically, the therapeutic objectives are: to reduce the amount of cephalorachid fluid produced, increase the amount of cephalorachid fluid that is absorbed and / or divert the excess of cephalorachid fluid to other body cavities. The primary objective is to alleviate the accumulation of pressure on the nerves (neurons), blood vessels and other affected brain tissues. Unfortunately, in view of current medical knowledge, it is difficult, if not impossible, to artificially increase the brain’s absorption capacity by medical manipulation.
The veterinarian will choose the treatment protocol based on several factors, including the dog’s symptoms at the time of the visit, the size and physical condition of the animal and the underlying cause of the hydrocephalus, if the latter can be determined within a relatively short period of time. short. Many dogs with hydrocephalus do not exhibit outward signs of the condition.
The pharmacological treatment of dogs with acute onset of hydrocephalus has the primary purpose of reducing the amount of cephalorachid fluid that is produced. Corticosteroids (such as prednisone or dexamethasone) have been used for this purpose. In an attempt to reduce the overproduction of cephalorachidian fluid in hydrocephalic dogs, some veterinarians have also used other drugs, including acetazolamide, omeprazole and furosemide. The administration of diuretics to reduce intracranial pressure by promoting the elimination of fluids in the urine may also be recommended. If the dog experiences seizures, anticonvulsant medications may be recommended. Unfortunately, drug therapy usually only brings about a temporary improvement in clinical signs.
Resorting to surgery may be necessary, especially if medical treatment does not alleviate symptoms within a few weeks. The goal of surgical treatment is to divert excess cephalorachid fluid from the brain ventricles to other body sites, often to the peritoneal cavity or right atrium. The peritoneal cavity is the space between the layers of membranes that line the abdomen and the pelvic cavity. The right atrium is one of the four chambers of the heart. There are several procedures and techniques for deflecting the liquid. The attending veterinarian will decide which one to use on an individual basis according to each specific case. Surgical treatment of hydrocephalus is almost always carried out by a veterinary specialist in neurology.
The prognosis for hydrocephalic dogs can be somewhat variable, from rather good to poor (patient death). If the condition is congenital and the dog has obvious neurological symptoms with concomitant irreversible brain damage, the prognosis will probably be from reserved to poor. However, if the condition is congenital without symptoms or characterized only by mild symptoms or if the condition is acquired as a result of inflammation (induced by trauma) or a treatable infection, the prognosis can be quite good, as long as the cause can be identified, corrected or treated before significant brain damage occurs due to increased intracranial pressure.