QUARTERLY BEAT
OCTOBER 2026
It is very important once MG has been diagnosed that a thorough work up is performed to rule out an underlying cause, such as a mediastinal mass mentioned above or other possible neoplastic processes. This is often performed with radiographs of the chest and an abdominal ultrasound, or if available, a whole-body CT.
Some owners have found it helpful to have their pets sleep with an inflatable cone (donut cone) around their neck to keep their neck in slight extension.
On average, approximately 88% of dogs will go into spontaneous remission approximately 6–18 months after diagnosis and will no longer require medication if the cause for MG is not neoplasia. 6 Want to hear more...tune in to hear a podcast with Dr. Carpentier on myasthenia gravis in dogs and cats HERE ! Of course, you might want to hear more about the long-term outcome of acquired MG in cats specifically...check out this podcast where we review the findings of Mignan, et al. in a study published in the Journal of Veterinary Internal Medicine, entitled: Long- term outcome of cats with acquired myasthenia gravis without evidence of a cranial mediastinal mass .
TREATMENT AND PROGNOSIS
Treatment consists of oral immunosuppressive medications, pyridostigmine, and intense supportive care. Common immunosuppressive medications that are used include prednisone, mycophenolate, cyclosporine, azathioprine, or leflunomide. Normally treatment will be initiated using one immunosuppressive medication and a second immunosuppressive medication will be added if necessary. Pyridostigmine is an anticholinesterase medication that is used to allow the ACh to be present longer at the synapse to hopefully allow it to bind to an available receptor. Possible side effects of pyridostigmine are related to a cholinergic crisis or toxicity. You can use the mnemonic “SLUDGE” to warn your owners about what side effects to watch for, including: salivation, lacrimation, urination, defecation/diarrhea, gastrointestinal signs, and emesis. These signs can also be consistent with MG, so once pyridostigmine is started it is important to evaluate these patients and get a thorough history if the owners are noticing these clinical signs to try and decipher if the clinical signs are secondary to the pyridostigmine or progressive MG (but sometimes this can be difficult). Most commonly, cats will be treated with prednisolone and pyridostigmine. It is important to educate owners that even in cats that have a mediastinal mass that is surgically removed, almost all cases of cats with MG-associated thymoma require postsurgical medical management to control the signs of MG. This is different than in dogs, where most cases will go into remission when the neoplastic mass is removed. It is important to know the significant risks that are associated with these surgeries. Most recently, therapeutic plasma exchange (TPE) has become more readily available for patients with MG and is a wonderful treatment option. The use of TPE in dogs with MG appears to be well tolerated, is safe, and can be considered as a first line therapy in addition to the medications listed above, or it can be considered in patients that are not responding to medical management alone. Overall, one of the most important aspects of treatment for these patients is supportive care. This can be drastically different in each patient based on their level of weakness, but it is aimed at providing appropriate nursing care, nutritional support, and physical therapy to try and keep them as comfortable and safe as possible. One of the leading complications of MG is aspiration pneumonia due to the megaesophagus. Diligent feeding practices of these animals with a Bailey-chair (Fig. 1) or something similar is of utmost importance. Any signs of aspiration pneumonia in these patients should be addressed promptly. I have also found that some of my patients tend to have regurgitation when they are sleeping at night.
Figure 1: Dog with megaesophagus in a Bailey chair. Photo courtesy of Kimberly Perkovick, LVT.
RESOURCES
1. Khorzad R, Whelan M, Sisson A, et al. Myasthenia gravis in dogs with an emphasis on treatment and critical care management. J Vet Emerg Crit Care. 2011;21(3):193-208. 2. Shelton GD, Ho M, Kass PH. Risk factors for acquired myasthenia gravis in cats: 105 cases (1986–1998). JAVMA. 2000;216(1):55-7. 3. Shelton GD, Schule A, Kass PH. Risk factors for acquired myasthenia gravis in dogs: 1,154 cases (1991–1995). JAMVA. 1997;211(11):1428-31. 4. Hague DW, Humphries HD, Mitchell MA, et al. Risk factors and outcomes in cats with acquired myasthenia gravis (2001–2012). J Vet Internal Med. 2015;29(5):1307-12. 5. Shelton GD. Myasthenia gravis and disorders of neuromuscular transmission. Veterinary Clinics: Small Anim Pract. 2002;32(1):189-206. 6. Shelton GD, Lindstrom JM. Spontaneous remission in canine myasthenia gravis: implications for assessing human MG therapies. Neurology. 2001;57(11):2139-41.
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