Neuroaxonal Dystrophy in Dogs

Nerve fibers, also called axons, are long thread-like projections of nerve cells (neurons).  The neuron’s axons normally send impulse transmissions to other nerve cells, muscles and gland cells.  In NAD, the progressive degeneration of nerve cells causes spheroids to form on the nerve endings. The nerve cells are no longer able to normally transmit to each other.  Abnormal nerve conduction causes the loss of coordination.

Canine newborns with NAD can be born with respiratory failure, scoliosis, and joint contractures (arthrogryposis).  Additionally, they can be born with cerebellar hypoplasia (not completely mature); the cerebellum is the part of the brain that controls fine motor skills and coordination.  There are dogs that do not show symptoms until they are into their adult life.

Breeds that are predisposed to NAD are the Papillons, Chihuahuas, Rottweilers, Border Collies, Dachshunds and the Jack Russell Terriers.

Neuroaxonal dystrophy (NAD) in dogs is usually an autosomal genetic disease, which causes progressive degeneration of the nerve cells of the peripheral and/or central nervous system. The progressive damage to the nerve cells leads to spheroids to develop and build up on the nerve fibers.

Symptoms may include:

• High stepping gait
• Poor coordination
• Stumbling
• Head tremors
• Incontinence
• Uncontrolled defecation
• Deficiency of vitamin E (causes cell damage)
• Secondary pneumonia

Neuroaxonal dystrophy may be caused by:

Neuroaxonal dystrophy in dogs is a usually caused by genetics.  Inheritance is believed to be autosomal recessive, which means two copies of the mutated gene must be present for the disease to be passed onto the litter.  Both the sire and the dam must be carriers of the mutated gene. Dogs that have only one parent with the mutated gene will not have the disease but will be carriers of the defective gene. Dogs diagnosed with neuroaxonal dystrophy should not be bred.

Neuroaxonal dystrophy can also occur in:

• Dogs with severe vitamin E deficiency, which causes nerve damage
• Insulin deficient diabetes (low blood sugar in the bloodstream)
• Senior dogs
• Dogs exposed to certain toxins

The veterinarian will want to go over the patient’s medical history.  If you have any previous medical records, it is a good idea to bring them along. The doctor may want to watch the patient walk.  The physical exam may include taking your dog’s weight, palpating his muscles to evaluate tone, and taking his pulse and blood pressure.  The veterinarian may also want to listen to your dog’s heart with a stethoscope. The patient’s reflexes may also be tested.   

The veterinarian may recommend running a complete blood count and a serum chemistry profile. The complete blood count can determine the platelets, red and white cells.  A CBC can also determine the patient’s glucose levels (blood sugar levels).  The serum chemistry panel can evaluate organ function.   He may also suggest x-rays, an ultrasound and an MRI. The diagnosis of neuroaxonal dystrophy will be based on the dog’s breed, symptoms, physical exam and the findings of the diagnostic tests.

There is no cure for neuroaxonal dystrophy in dogs.  Some dogs respond to prednisone. Prednisone is a corticosteroid and is usually used as an anti-inflammatory. The veterinarian may also prescribe methocarbamol to help the muscles to relax and provide relief from muscle spasms. Antibiotics may also be prescribed to help prevent pneumonia and infections.  Vitamin E and Omega -3 supplements may be recommended. The veterinarian may want the patient on a noncommercial high quality meat-base diet, which has more nutrients. Massaging the limbs when they stiffen can be beneficial. The veterinarian may recommend that the patient have canine massage therapy (CMT). 

Patients diagnosed with insulin deficient diabetes will need to have daily insulin shots.  Insulin deficient diabetes is usually caused by the pancreas not functioning normally.  The veterinarian may want to run further diagnostic tests to check on the dog’s pancreas condition.

Patients that have a slow progression of neuroaxonal dystrophy can live comfortable lives with a medical treatment plan.  It is important to not leave the dog alone outside or by a pool, to avoid him falling or drowning.  Follow up visits will be necessary to monitor the patient. Prednisone can have side effects such as increased appetite and thirst and suppress the immune system.  A suppressed immune system can cause the patient to be more susceptible to infections. Puppies born with severe neuroaxonal dystrophy are usually humanely euthanized.