Canine Dysautonomia

 

Dysautonomia is characterized by a malfunctioning of the autonomic nervous system (ANS), the system that controls the heart rate, respiration, digestion, urination, salivation, perspiration, eye pupil dilation,blood pressure, intestinal contractions, glandular acticity, and physical arousal. The body functions that occur within the ANS are largely performed without conscious thought, with the exception of breathing, which works in coordination with conscious thought. This condition is also referred to as Key-Gaskell syndrome.

 

This is a rare condition, but when it does occur, it tends to affect dogs that are young, but beyond puppy age, and free roaming, rural gods tend to be at greatest risk for acquiring the disorder. Otherwise, there is no gender or age that is specifically affected. There is some geographical correlation tied to canine dysautonomia, with higher incidences occurring in the Midwest, Missouri, Oklahoma, and Kansas. However, cases have been reported throughout U.S.

 

Treatment is based on the primary symptoms and the prognosis for recovery is guarded.

 

Symptoms and Types

 

• Acute symptoms typically develops over three to four days
• Dilated unresponsive pupils
• Lack of tear production
• Fear/avoidance of light (photophobia)
• Third-eyelid elevation (protrusion of third eyelid)
• Vomiting
• Regurgitation
• Anorexia and weight loss
• Dribbling urine (polyuria)
• Straining to urinate
• Loss of anal sphincter tone
• Diarrhea
• Constipation in some cases
• Distended, easily expressed bladder
• Possible abdominal pain
• Dyspnea (difficult breathing)
• Dry nose and mucous membranes
• Coughing
• Nasal discharge
• Depression
• Loss of spinal reflexes
• Muscle wasting
• Possible weakness

 

Causes

 

The cause is unknown.

 

 

 

Diagnosis

 

Your veterinarian will perform a complete physical exam on your dog. You will need to give a thorough history of your dog's health, onset of symptoms, and possible incidents that might have led to this condition. The history you provide may give your veterinarian clues as to which organs are being affected by this condition.

 

X-rays will show megaesophagus (enlargement of the esophagus), distended intestinal loops with no peristalsis (the normal contraction of the intestinal muscles) and a distended urinary bladder. Loss of nerve control in the iris of the eye will cause it to be hypersensitive to cholinergic drugs, affecting the response time for the iris of the eye to contract. A dog that is not affected with Key-Gaskell will have a normal response time of 30 minutes, and a dog that is affected with this condition will have an abnormally fast pupil constriction reaction.

 

An atropine challenge test will be given to test the heart's response – a healthy dog will have a rise in heart activity (tachycardia) in response to the atropine, where a dog affected with Key-Gaskell will have no increase in heart rate.

 

Histamine injections may be given to test for sympathetic loss of capillary function. If there is loss of capillary function, there will be no visible reactive response in the skin, or a welt but no flare in the skin. These tests will help your veterinarian to make a compete assessment of the autonomic nervous system's (made up of the sympathetic and parasympathetic nervous systems) ability to function in a healthy manner.

 

Treatment

 

The cause of dysautonomia is unknown. Thus, treatment is symptomatic.

Intravenous (IV) fluids should be given to the dog to prevent dehydration. A feeding tube may help ensure adequate nutrition if megaesophagus is present. If intestinal motility is absent, a feeding tube may be necessary. Artificial tears should be administered if tear production is insufficient. Humidification of the air may help with dry mucous membranes. The bladder should be manually expressed for the dog.

 

Medications will be given for supporting the organs, and for encouraging bladder contraction and improving intestinal motility. If infections or pneumonia are suspected, antibiotics will be prescribed.

 

Living and Management

 

Prognosis for dogs with dysautonomia is guarded. Most dogs that are afflicted with this disease will not survive, as many die of aspiration pneumonia or need to be euthanized due to poor quality of life. Dogs that do survive can take more than a year to fully recover and often have some degree of permanent autonomic dysfunction, which may require that they be given constant care.