Head injury in dogs – brain injury symptoms and treatment

Overview

A head injury does not always mean a brain injury

Not every dog with head trauma develops a brain injury. Assessment considers brain function, rather than only the injury visible outside the head. Trauma can cause both immediate damage and additional damage developing later. The latter includes brain tissue swelling.

In a large North American trauma registry, 341 of 3,599 injured dogs, or 9.5%, had a head injury. This figure describes trauma patients brought for care, rather than the head injury risk in all dogs. Brain injury can be life-threatening. A mild injury, however, can have a good recovery.

Causes

Primary damage from an impact

An impact can tear brain tissue and blood vessels and cause a brain contusion. A skull fracture fragment can press on brain tissue. A penetrating foreign body can also damage structures within the skull. The consequences therefore depend on more than the size of a visible head wound.

Among 50 brain injury patients undergoing MRI, 20, or 40%, had been injured in a road accident. An attack by another dog was responsible in 9 dogs, or 18%. A fall also caused injury in 9 dogs, or 18%. An object striking the head was responsible in 8 dogs, or 16%. A horse kick caused injury in 4 dogs, or 8%.

Additional damage developing later

Secondary events can start within minutes or hours of the primary injury. Low blood pressure reduces adequate blood flow to the brain. Oxygen deprivation can impair oxygen delivery to already damaged brain tissue. Low or high blood glucose and severe electrolyte and acid–base disturbances can also worsen the situation.

Secondary cellular damage involves calcium accumulation inside cells. Release of the excitatory neurotransmitter glutamate also contributes to the damage cascade. Brain injury can disrupt the brain's ability to regulate its own blood flow. Blood flow then becomes more dependent on systemic blood pressure.

Risk factors

A dog roaming freely without supervision can have an accident. Traffic, falls from a height and confrontations between dogs are therefore relevant hazards. A skull fracture and extensive brain tissue damage are associated with poorer recovery after a brain injury has occurred.

Brain injury affects both puppies and adults: the 50-dog study had a median age of 3 years. Ages ranged from 2 months to 12 years. Dogs weighed 0.9–45 kg, so injury was not confined to dogs of a particular size. A list of breeds treated does not by itself establish breed predisposition.

Typical symptoms

Signs can change over time, so worsening of an initially observed sign also matters. You may notice:

• Your dog is more subdued than usual or responds differently to their surroundings.
• A seizure or repeated seizures.
• Difficulty moving or inability to walk normally.
• Unequal pupils or an abnormal light response.
• A head wound or bleeding from the nose, ear or eye.
• An abnormally high or low body temperature.

Heart rate can also slow. Some brain injury patients do not blink normally.

Pale mucous membranes and cool limbs may indicate a concurrent severe circulatory disturbance, or shock.

Complications and consequences

Pressure and circulation within the skull

The skull contains brain tissue, blood and cerebrospinal fluid. The rigid skull cannot expand to accommodate increasing contents. Extra volume from swelling or bleeding can therefore raise intracranial pressure. Reduced circulation can increase brain tissue damage.

Seizures and later problems

Among the 50 dogs undergoing MRI, 36% had seizures after injury. Recurrent seizures, or post-traumatic epilepsy, developed in 5 dogs, or 10%. Its median onset was 119 days, with a range of 0–427 days. A seizure beginning later can therefore also be linked to a previous injury.

Possible consequences include permanent neurological deficits. Difficulty eating can cause malnutrition. Poor blinking predisposes the cornea to drying.

Seizures increase the brain's metabolic demands and can thereby worsen existing damage.

Diagnosis at the vet

Vital functions and examination of the whole dog first

The initial assessment uses a general and neurological examination to establish injury severity and location. Breathing and circulation are also assessed because oxygen deprivation and falling blood pressure can worsen brain damage. Blood glucose and electrolytes are checked for disturbances that can be corrected. Examining a visible head wound alone therefore does not provide a full assessment.

Neurological examination includes alertness, movement, proprioception, reflexes and cranial nerve function. Findings help locate the problem within the nervous system. Examination is repeated during monitoring because neurological abnormalities can change.

Scoring supports monitoring

The modified Glasgow coma scale, or MGCS, assesses 3 areas: movement, brainstem reflexes and level of consciousness. Total scores range from 3–18. A lower score indicates a worse neurological condition. Scoring can track a brain injury patient's progress.

The animal trauma triage, or ATT, score assesses 6 areas: tissue perfusion, cardiac function, breathing, eye and skin injuries, the skeleton and the nervous system.

Imaging and prognosis

CT or MRI can investigate damage within the skull. MRI assesses findings including lesion extent, brain midline shift and skull fractures. Displacement of brain tissue from its usual position, or herniation, was associated with poorer recovery. Imaging therefore complements the clinical examination.

MRI requires circulation stable enough for anaesthesia. Treatment of the most severely injured dogs therefore begins with supporting vital functions.

Among the 50 dogs undergoing MRI, 66% had an abnormal imaging finding. Normal imaging was therefore possible in a dog clinically considered to have a brain injury.

Treatment

Safe transport

Keep an injured dog's movement to a minimum, particularly if spinal injury is also possible. A rigid supporting surface can help transport a large dog. Do not push a small dog through a narrow carrier door: open the top instead. Arrange transport as quickly as possible following veterinary advice.

Do not keep the head lower than the rest of the body because this can increase intracranial pressure. Support of the head and neck is considered particularly if spinal injury is possible.

A tight collar is avoided so that blood flow through neck veins is not obstructed.

Maintaining brain oxygen delivery and circulation

A central early treatment goal is to maintain oxygen delivery to brain tissue. Your dog may need supplemental oxygen and, in severe cases, mechanical ventilation. Low blood pressure is corrected with fluids or blood pressure-supporting medicines where necessary. Fluid treatment is carefully tailored because excess fluid can worsen brain swelling. High body temperature is avoided because it can worsen the metabolic disturbances of brain injury.

Respiratory care avoids both excessively high and low blood carbon dioxide to maintain adequate brain blood flow. Excessive carbon dioxide reduction constricts brain blood vessels and reduces flow.

Managing intracranial pressure and signs

Hyperosmolar treatment can reduce intracranial pressure by drawing fluid out of brain tissue. Pain is relieved with medicines selected by your vet. Sedation may be used where needed to reduce additional injury. Unnecessary neck handling and compression of venous return are avoided.

Seizures that develop are treated with antiseizure medicines. Preventive antiseizure medication is not routinely recommended for every animal patient. Corticosteroids have not shown benefit in acute brain injury. This distinguishes traumatic brain injury from many inflammatory nervous system diseases.

Mannitol used to manage pressure can increase urine production and cause dehydration.

Surgery and supportive measures

Surgery may be needed for a skull fracture, penetrating foreign body or blood collection within the skull, for example. A dog with difficulty eating may initially need a feeding tube. Lubrication of eyes that blink poorly may form part of care. A patient unable to move also needs hygiene care to prevent urine and faeces remaining on the skin.

Assessing recovery

In a mild injury, the outlook is favourable if neurological function does not deteriorate further during 48 hours of monitoring. This is an assessment during care, rather than a reason to wait at home for signs to worsen. The extent of recovery may become clear only over several days. Full recovery may not be assessable until 6 months or even later.

Prevention

Near traffic, keep your dog on a short lead attached to a well-fitting collar or harness. Check fencing around an off-lead exercise area so that your dog cannot reach a nearby road. Reflective equipment improves visibility in the dark.

In a car, your dog travels in a seat-belt harness on the rear seat or in an appropriately sized crate secured to the vehicle structure. A deploying front-seat airbag poses an injury risk to a dog. Do not secure your dog in a car by the collar.

Size the crate so that your dog can rest comfortably without unnecessary excess space.

On walks, favour pavements and marked pedestrian crossings over busy crossing points or those with poor visibility.

Important for dog owners

Details of the incident and home care

Tell the practice when the injury occurred and what kind of impact or accident was involved. Record any seizures and their timing. At home, monitor consciousness, movement and seizures in particular because these are features of brain injury. New deterioration requires urgent veterinary assessment.

Agree follow-up visits and increases in activity with the treating vet. Monitoring may include blood pressure and glucose measurements. Also record eating and blinking because these may need support. Rehabilitation is assessed from progress in function, rather than the appearance of a head wound alone.

Approach an injured dog cautiously because emergency stress can make even a familiar dog bite. Do not put a hand into a conscious dog's mouth.

Frequently asked questions

Can a dog's condition worsen after a head injury?

Yes. Brain swelling and other secondary damage can develop after the primary injury. Neurological signs can change over time. Reduced consciousness, breathing difficulty or inability to stand require urgent care. Do not wait for the next planned follow-up when a new change occurs.

Can you carry an injured dog?

Move your dog carefully, keeping unnecessary movement to a minimum. A rigid supporting surface can be used to transport a large dog. Open the top of a small dog's carrier so that they do not need to be pushed through a narrow door. Possible spinal injury is considered when arranging transport.

Does every dog with a brain injury develop epilepsy?

No. Among the 50 brain injury patients undergoing MRI, 5, or 10%, developed recurrent seizures. The study concerned patients stable enough for imaging. A seizure beginning later after injury should also be reported to the treating vet because epilepsy can have a delayed onset.

How long does recovery from brain injury take?

The extent of recovery is not always clear on the first day and may become better defined over several days. Final function may become apparent only after 6 months or longer. Some dogs' signs may initially worsen before improvement begins. Recovery is therefore assessed at repeated follow-up visits.

Does a head injury always need surgery?

Surgery is not the only treatment for every brain injury. Initial care includes maintaining brain oxygen delivery and circulation. Surgery may nevertheless be needed for a skull fracture, a foreign body penetrating the skull or a blood collection. Your vet assesses the need according to your dog's condition and findings.