Brain Injury in Dogs

By Malcolm Weir, DVM, MSc, MPH; Tammy Hunter, DVM; Robin Downing, DVM, DAAPM, DACVSMR, CVPP, CRPP

What is a brain injury?

Brain injuries are devastating and, unfortunately, often fatal. Primary brain injuries result from a direct insult to the brain, and secondary brain injuries occur following the primary brain injury. Secondary brain injuries may include bleeding from a brain blood vessel or swelling of brain tissue.

What are the signs of a brain injury?

The typical signs of brain injury in a dog include altered consciousness that may signal bleeding in the skull, decreased blood flow to the brain, or fluid causing swelling within the brain itself. The dog may have seizures, some evidence of trauma on the head or other part of the body, bleeding into the eyes, or bleeding from the nose or ears.

"The overall function of the nervous system may be altered in some way, and those abnormalities may change over time."

A dog with brain trauma may have difficulty regulating their body temperature, causing fever or a body temperature that is too low. The heart may beat very slowly. The pupils of the eyes may be uneven in size and may react abnormally to light. The overall function of the nervous system may be altered in some way, and those abnormalities may change over time.

What are the risk factors for brain injury in a dog?

Risk factors for brain injury in a dog include unsupervised roaming that may result in trauma or exposure to toxins, heart disease, lung disease, blood-clotting disease, or diabetes mellitus.

What causes brain injury in dogs?

There are many potential causes of brain injury, including the following:

  • A forceful trauma, such as being hit by a car
  • Prolonged low levels of oxygen in the blood
  • Decreased or lack of blood flow to the brain
  • Severely low levels of sugar in the blood (hypoglycemia)
  • A prolonged seizure or multiple seizures over an extended time
  • Severe or extended fever
  • Profound decrease in body temperature
  • Altered concentrations of essential minerals in the blood, such as sodium
  • Profound or prolonged low blood pressure or high blood pressure
  • Some infectious or immune-mediated diseases
  • Toxins
  • Cardiac arrest or respiratory arrest
  • Blood clots that travel to the brain
  • Bleeding into the brain from a blood clotting disorder
  • Brain tumor

How are brain injuries treated?

Treatment of a dog’s brain injury depends on what led to the brain injury. The initial goal of treatment is to maximize oxygen levels in the brain tissue. If the blood pressure is too low, then supporting blood pressure improves brain blood flow. If the blood pressure is too high, or if there is high pressure inside the skull for another reason, then decreasing pressure in the skull is the priority.

Any necessary intravenous fluid therapy must be administered carefully to avoid any fluid build-up in the brain, even if there is bleeding that requires fluid replacement. Your veterinarian balances your dog’s blood pressure to prevent it from going either too low or too high. The head should never be lower than the body to prevent increased pressure inside the skull. Some dogs with a brain injury do not blink their eyes normally, so lubricating the eyes may be a part of the treatment. It will also be important to prevent any urine or stool soiling if the dog is unable to position properly for elimination.

Are any other treatments appropriate for a dog with a brain injury?

Any dog with a brain injury must receive adequate nutrition to support healing. This may require tube feeding at first if eating is difficult or impossible. Surgery may be necessary if there is a skull fracture, a foreign object penetrating the skull, or build-up of fluid or blood inside the skull.

Medications may be needed to decrease pressure inside the skull by helping the body eliminate extra fluid or by helping to pull extra fluid from the tissues of the brain. There may be a need for pain relievers, heavy sedation, or even a temporary state of general anesthesia to spare the brain from additional injury. Adequate levels of oxygen must be provided, so a tube may be passed into the windpipe to assist breathing. If the dog’s blood sugar levels are too low, intravenous glucose may be needed. Alternately, if the dog’s blood sugar level is too high, intravenous insulin may be needed.

What follow-up care is needed for a dog with a brain injury?

Any dog with a brain injury should be monitored for the progress of his recovery. This may include blood pressure measurements, as well as laboratory tests to monitor blood levels of various substances like blood sugar and minerals.

Some potential long-term complications of brain injury in a dog include:

  • Ongoing seizures
  • Uncontrolled swelling of the brain
  • Bleeding into the skull
  • Progression of nervous system signs indicating permanent brain damage
  • Malnourishment from difficulty eating
  • Drying of the corneas from decreased blinking

What is the long-term outlook for a dog with a brain injury?

For a young dog with a minor primary brain injury, and secondary injury limited to fluid build-up in the brain, the long-term outlook is favorable. If the dog experiences no additional nervous system deterioration over a 48-hour period, the prognosis remains favorable. Finally, if blood pressure and blood sugar levels remain within normal limits, the prognosis is favorable. In some cases, the dog’s nervous system signs may worsen before improvement begins. The extent of brain recovery may not be obvious for several days. The dog’s full level of recovery may not be apparent for up to 6 months or longer.

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