Myasthenia gravis (MG) is an autoimmune disorder that disrupts the neuromuscular junction. It occurs when antibodies bind to and destroy acetylcholine receptors so that muscles cannot receive signals from the associated nerves. Signs include muscle weakness and fatigue, which improves after rest, depressed respiration, and regurgitation caused by esophageal weakness.  

A fast, expert response is critical because the condition can progress quickly, leading to tetraplegia, aspiration pneumonia, and respiratory arrest.   So, when Bruno, a three-year-old male intact German Shepherd, arrived at Bridgetown Veterinary Emergency + Referral with severe weakness in the back legs, the ER team immediately brought in BVER’s co-medical director, neurologist Megan Steele DVM, DACVIM.  

According to the dog’s owners, the condition had appeared overnight. Then, two evenings before bringing the dog to Bridgetown, the owners observed a sudden onset of weakness in the back legs. The condition seemed to improve the following day, but when it recurred on the second evening, the owners sought BVER’s expertise.  Dr. Steele observed that Bruno was weakly ambulatory, with a characteristic bunny-hop gait. “He looked like he was sitting but trying to walk, but he was happy, pain-free, and very much wanted to be active,” she observed.  

The neurologic examination was consistent with generalized lower motor neuron disease and not a myelopathy. Top differentials for Bruno included acquired myasthenia gravis, acute acquired polyradiculoneuritis, myositis, neuritis, tick paralysis, and botulism.  With the first possibility most likely, Dr. Steele performed a neostigmine trial by administering a small dose of the intermediate-acting cholinesterase inhibitor. Typically, in cases of MG, the animal regains the ability to walk within minutes. However, in Bruno’s case, the results were dramatic, Dr. Steele recalled.   

With the trial supporting her preliminary diagnosis and with chest radiographs negative for pneumonia and megaesophagus, Dr. Steele was able to send Bruno home with pyridostigmine to treat his symptoms.  The underlying autoimmune condition could be addressed only after the MG diagnosis was confirmed by an acetylcholine receptor antibody (AChR antibody) test. At present, processing the test can take a few weeks. Nevertheless, waiting for confirmation of the diagnosis was crucial.  

Rushing to treat the animal with immunosuppressants is inadvisable due to increased susceptibility to infection and various side effects. “These are not benign drugs,” Dr. Steele cautioned.  

Once the AChR test confirmed that Bruno was strongly positive for MG, pyridostigmine was supplemented with the immunosuppressant mycophenolate, and the dog was monitored regularly.   

Bruno enjoyed a speedy recovery. At three months, his titers were weakly positive but improving. At six months, the titers were negative, Bruno was free of clinical signs, and the drugs were gradually reduced. Today treatment has been discontinued, Bruno’s antibody test remains negative, and he has suffered no recurrence of signs.  Bruno is a lucky dog, Dr. Steele said. Due to the pet owners’ attentiveness and the ability of Bridgetown Emergency + Referral Veterinary to immediately and seamlessly transfer the case from ER to neurology, a potentially dangerous condition was successfully resolved.  

If an animal exhibits signs of myasthenia gravis or generalized weakness of unknown origin, you may refer the patient to our neurologists by calling 503.489.9535.