Stupor and Coma in Dogs

Drops in brain function create a corresponding drop in responsiveness. This can be seen in the way your dog acts and relates to the outside world. Confusion is usually the first sign. Your dog may appear disorientated or bewildered and will not respond to normal stimuli. This is followed by lethargy, a preference for sleep rather than external interaction. A lethargic dog can be easily roused, but he will quickly withdraw and lapse back into sleep. Lethargy is followed by stupor which is a state where the dog becomes very difficult to rouse and coma which indicates the dog is unconscious and unresponsive to the most intense stimuli. Stupor and coma are the results of many disorders that affect the central nervous system (CNS,) especially the parts of the brain which relate to consciousness.

Stupor and coma are words used to describe the level of alertness in dogs. The dog will often progress through mild or severe disorientation to heavy sleep and complete unconsciousness. Veterinarians define the last two stages as stupor and coma. They may appear separately or in succession.

Even if the disorder begins slowly, it’s best to see a veterinarian as soon as possible since conditions can devolve quickly. 

• Fatigue or low energy
• Lack of interest in food or exercise
• DisorientationUnable to recognize known objects
• Stumbling or running into objects
• Tendency or desire to sleep
• Difficult to rouse from sleep
• Unable to rouse from sleep (unconscious)

Types

There are several different types of comas.

Toxic metabolic encephalopathy

• This is the most reversible condition
• It is usually due to an upset in metabolism which affects brain function
• Causes may be organ dysfunction or failure as well as the presence of toxic substances
• Rebalancing the metabolism can sometimes reverse the condition

Anoxic brain injury

• This is a complete lack of oxygen to the brain (from cardiac arrest, respiratory failure or other sources)
• Cell death begins within a few minutes.

Persistent vegetative state

• Basic life functions continue but there is no conscious awareness

Brain death

• Cessation of all brain function

Medically induced

• Sometimes comas are medically induced in order to protect the brain

Many disorders which cause stupor and coma contain the word encephalopathy. This refers to any disease or condition which affects the brain. Encephalopathy can be caused by injury, metabolic dysfunction, toxic substances, and infection. It usually involves swelling of brain tissue and bleeding or internal hemorrhage in the case of injury.

• Severe liver disease (hepatic encephalopathy)
• Kidney failure (renal associated encephalopathy)
• Hypothyroidism (myxedema coma)
• Diabetes (ketoacidosis)
• Low blood sugar (hypoglycemic encephalopathy)
• Imbalance of sodium or calcium  (electrolyte-associated encephalopathy)
• Lack of oxygen (anoxic encephalopathy)
• Toxic substance in high doses (including chocolate and caffeine)
• Severe allergic reaction
• Traumatic injury to the brain
• Lesion in the brain
• Brain tumor
• Stroke
• Continuous seizures
• Infectious disease (meningitis and encephalitis)
• Inflammatory CNS disease

The veterinarian will try to find the underlying condition which is affecting your dog’s level of alertness. Any information you can give about the symptoms and time of onset will be important. You should give the veterinarian your dog’s medical history and any relevant conditions like diabetes. Describe recent injuries and possible exposure to toxins. 

The veterinarian will complete a physical examination to check for injuries and a neurological test to ascertain the level of alertness in your dog. Complete blood (CBC) and urine tests will often show if the condition is related to metabolic problems or an infectious disease. A CT scan or MRI will show if tumors or lesions are present as well as trauma or bleeding inside the brain. The veterinarian may order X-rays to check for tumor metastasis or other problems.

If you find your dog unconscious, first check for a pulse. If there is no pulse, try to administer CPR until you can get medical help. If there is a pulse, check for obvious injuries. If you suspect any injuries to the head or spinal cord, move the dog as little as possible during the process of transporting him to the clinic. 

Treatment will depend on the underlying issue and the severity of the disease. Dogs with only mild confusion or stupor from a metabolic imbalance can often be treated by rectifying the imbalance. Hypoglycemia can be reversed by raising the blood sugar, as long as the treatment takes place before there is brain damage. Thyroid replacement hormone can be effective with hypothyroid, although the drug will have to be administered intravenously if the coma stage has been reached. Other types of endocrine encephalopathy can often be treated with fluids and electrolytes. Once the immediate condition has been rectified, the veterinarian will look at medication and diet changes to prevent it from occurring again.

Medication can treat meningitis and encephalitis depending on the advancement of the disease. Some infectious diseases like canine distemper go through coma as the final stage before death, so this will not be treatable. Heart failure and advanced respiratory disease that lead to coma will also likely result in death. Many hereditary conditions and idiopathic inflammatory CNS are also not treatable; however medication may be able to reduce symptoms and delay onset. New medications are being developed all the time so you will need to discuss your dog’s exact condition with the veterinarian.

Some brain tumors can be removed with surgery. Others may be treatable with medication or chemotherapy. Brain injuries may be treatable with surgery also, or an induced coma to give the brain time to heal. Medications can also reduce seizures, although repeated seizures that lead to coma will often cause brain damage.

If your dog survives after the onset of stupor and coma, it’s possible he will suffer lasting brain damage. He may have reduced mobility in parts of the body, or an altered level of awareness than before. You may need to rearrange your house and remove obstacles which could pose a threat, as well as to alter his exercise routine. You may also have to put him on a special diet, or give daily medication. Depending on the condition, your dog could recover completely, but it’s more likely that he be left with a certain amount of disability that requires a modified lifestyle.