Disorder - Myasthenia gravis

Organ Systems Involved
Musculoskeletal

Alternative disorders described within LIDA

Myopathy; Peripheral neuropathy; Congenital myotonia

Presenting Signs

Each muscle in a cat’s body is controlled by its own nerve but the connection is not direct. A small gap exists between the nerve and muscle, and signals must be carried across this gap by a messenger substance (acetylcholine). The acetylcholine then attaches to sites called acetylcholine receptors and the muscles can then contract. CMG is a disorder of transmission between nerves and muscles, resulting from either a deficiency or disorder of the acetylcholine receptors. It is generally seen in four to five month old animals. Acetylcholine receptors play a vital role in nerve-muscle transmission in voluntary muscles (such as limbs), so any problem can interfere with overall muscle contraction control, resulting in muscle weakness.

Symptoms include weakness that worsens on prolonged exercise. This can affect all four limbs or just the two back legs. Affected animals may also take short steps and have a stiff gait with muscle tremors, laboured breathing, difficulty swallowing, regurgitation of food/water, droopy upper eyelid and lips, and excessive drooling.

Treatment

Initial therapy should include agents that break down acetylcholine, which is aimed at improving the transfer of the signal from the nerves to the muscle. If the cat has aspiration pneumonia secondary to weakness in the muscles required for breathing, antibiotics are needed to treat this also. Duration of treatment depends on the individual cats response to therapy.

PubMed References
Myasthenia gravis

Contributor
Christina Zhu