The signs that a dog has brain damage can be missed at times, even by the most attentive dog owners. On top of this, should the signs be recognized, they may not always be readily associated with the dog sustaining some type of brain injury. If your dog has sustained some type of brain trauma, it's important to see the vet to rule out the possibility of brain damage. As it happens in people, there may not be immediate signs. Veterinarian Dr. Ivana shares signs that a dog has brain damage and what to look for.
Brain Damage in Dogs
The dog’s brain is the source of its consciousness and intelligence. It enables the dog to experience and communicate emotions, and it controls almost all bodily processes – from basic functions such as sleep and appetite, to sensory perceptions. To carry out all of these functions, the brain’s cells called neurons communicate with every living cell in the body. That communication is performed through nerves and select chemicals called neurotransmitters.
How does the dog’s brain work? Anatomically, the dog's brain is similar to a human brain, but it is about a quarter of its size. The largest part of a dog's brain consists of the cerebrum, which is split into two halves known as hemispheres. The two hemispheres are joined by a bundle of nerve fibers known as the corpus gallosum.
The outer layer of the dog's cerebrum, consists of the the cerebral cortex, which allows learning, and sense perception. In the lower brain, instead the cerebellum is responsible for the coordination of muscles and the brain stem, which joins to the spinal cord, monitors the dog's heart rate and breathing.
The brain's central region contains the thalamus, through which sensory information passes on its way to the cortex, and the hypothalamus, which regulates bodily processes and influences the hormonal system via the pituitary gland. Layers of tissue called the meninges are thrre to help protect the brain.
Brain cells are responsible for a plethora of different functions. Therefore, they need plenty of nourishment to function correctly. Although the brain makes up only about two percent of a dog's weight, the brain receives around twenty percent of the blood that the heart pumps out. Its most significant need is for oxygen. The brain is by far the body's most oxygen-hungry organ. Lack of oxygen, even for as little as 20 seconds, can cause irreversible brain damage. The sugar glucose is also essential. Low blood sugar levels dramatically interfere with brain function.
How Do Dogs Sustain Brain Damage?
Brain damage may be caused by physical injury. For example, traffic accidents may cause concussions or contusions. In such injuries, the brain may be seriously damaged even though the skull is intact. If the head is struck on one side, the brain can be bruised as it is shaken within the skull. If the skull is fractured, bone fragments may penetrate the brain tissue, causing significant bleeding and damage.
Specific poisons, or toxins, including natural substances such as snake venom and human-made products such as organophosphate insecticides, can damage brain cells if inhaled or ingested.
Chronic disorders affecting other body organs, such as kidney failure, liver failure, thyroid gland disease, adrenal dysfunction, or cancer, may lead to brain damage by depriving the brain of essential substances or causing toxins to circulate in the bloodstream. Nutritional deficiencies such as lack of the vitamin thiamine can impair brain function and potentially cause permanent brain damage.
Vascular disease, particularly the buildup of material on the inside of cerebral arteries or strokes, can prevent oxygen-rich blood from reaching affected parts of the brain. Without an adequate blood supply, those areas of the brain will die in seconds.
Brain tumors and other swelling lesions such as polyps and cysts can compress the surrounding brain tissue as they grow. Localized inflammation of the brain tissue, such as that caused by meningitis or encephalitis, also places pressure on adjacent areas of tissue.
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Signs That a Dog Has Brain Damage
Brain damage can cause changes in a dog’s behavior or physical abilities. The symptoms depend on which region of the brain has been damaged.
For example, damage to the cerebrum may cause changes in the dog's mental status with loss of consciousness, confusion, wobbliness, dazing. Affected dogs may also show changes in vision.
Cerebellar damages often cause: ataxia, that is, lack of muscle coordination which leads to balance and gait problems, abnormal head tilt and nystagmus, the involuntary and rhythmic movement of the eyeballs, which may appear jerky. Usually, both eyeballs move together.
The most dramatic behavior changes include: seizures – including loss of consciousness followed by involuntary activities such as muscle contractions, paddling with the limbs, trembling and facial twitching. During a seizure, dogs frequently salivate, urinate or defecate. Stupor – a dog in stupor is unconscious but can be temporarily aroused before falling back into stupor. Coma – a dog in coma is unconscious and cannot be aroused.
Specific brain damages and damages to the spinal cord may result in paralysis – temporary or permanent complete loss of muscle function and paresis –an incomplete form of paralysis.
Treatment of Brain Damage in Dogs
The site and extent of brain damage can be assessed using different diagnostic techniques such as blood analysis, electroencephalogram (EEG), brainstem auditory evoked response (BAER), cerebrospinal fluid (CSF) analysis, x-rays, CT and MRI scans. Every brain damage assessment starts with a complete physical examination, followed by a neurological exam.
When performing the neurological exam, the vet will carry out specific tests to evaluate the dog’s head posture, coordination, ability to walk in a circle clockwise and counterclockwise, stance and gait, menace response when threatened, and facial expression and symmetry. The vet may shine a light into the dog’s eyes to check pupil light reflex and symmetry. These tests help to pinpoint the site of possible brain damage.
The treatment depends on the cause, severity, and location of the damage. For example, antibiotics and corticosteroids can be given to reduce inflammation due to infection. In cases of brain tumors, surgery may relieve the local pressure.
Sadly, the prognosis is often unpredictable, especially in the case of head injury. Painkillers and other drugs may be used to make the dog more comfortable. Dogs with overwhelming and irreversible brain damages are usually put to sleep.
Brain damage can arise from physical injury; from poisoning, either by a substance in the environment or from the effects of a chronic disease elsewhere in the body; from infection, of the brain itself or its surrounding membranes; or from tumor growths in the brain tissue.
The clinical manifestation varies based on the type of injury that caused the damage and the damage’s extent and localization. Regardless of the clinical signalization, brain damages in dogs are potentially life-threatening and require prompt veterinary attention.
About the Author
Dr. Ivana Crnec is a graduate of the University Sv. Kliment Ohridski’s Faculty of Veterinary Medicine in Bitola, Republic of Macedonia. She currently practices as a veterinarian in Bitola and is completing her postgraduate studies in the Pathology of Domestic Carnivores at the Faculty of Veterinary Medicine in Zagreb, Croatia.