Muscle weakness

What are the causes of muscle weakness in dogs?

There are various factors that can lead to muscle weakness in dogs. Some of these are:

• Congenital myasthenia: This is a rare genetic disorder that is present from birth. The receptors on the muscle cells that are responsible for transmitting nerve signals are missing or do not function properly.
• Acquired myasthenia: This is a more common form of muscle weakness that is acquired in the course of life. In this case, the receptors on the muscle cells are attacked and destroyed by the patient's own immune system. The cause of this is often unclear, but it may be related to other autoimmune diseases such as hypothyroidism or diabetes.
• Medication: Some medications can cause muscle weakness as a side effect. These include antibiotics, antiepileptic drugs or muscle relaxants, for example.
• Other diseases: Sometimes muscle weakness can also be a symptom of another condition, such as an infection, poisoning, tumor or neurological disorder.

What are the symptoms of muscle weakness in dogs?

Symptoms of muscle weakness in dogs can vary depending on the severity and muscle groups affected. Some of the most common signs are:

• Weakness or exhaustion after physical exertion
• Flaccid or drooping facial muscles, especially around the eyes and mouth
• Difficulty chewing or swallowing food or water
• Hoarse barking or coughing
• Shortness of breath or rapid breathing
• Enlarged tongue or salivation
• Wobbly gait or stumbling
• Collapse or paralysis of the legs

How is muscle weakness diagnosed in dogs?

To diagnose muscle weakness in dogs, the vet will need to perform a thorough clinical examination and order some tests. These include:

• Blood tests: these can help to rule out other possible causes for the symptoms, such as infection, hypothyroidism or diabetes.
• Antibody test: This test measures the amount of antibodies in the blood that are directed against the receptors on the muscle cells. A high value indicates acquired myasthenia.
• Electromyography (EMG): This is a test that measures the electrical activity of the muscles. Small needles are inserted into the muscles and electrical impulses are sent. An abnormal pattern may indicate impaired nerve-muscle communication.
• Tensilon test: This is a test that observes the effect of a drug called Tensilon on the muscles. Tensilon inhibits an enzyme responsible for breaking down the neurotransmitter acetylcholine, which is important for nerve-muscle communication. When Tensilon is injected, there should be a temporary improvement in muscle strength. This may be an indication of myasthenia.

How is muscle weakness in dogs treated?

The treatment of muscle weakness in dogs depends on the cause and severity of the condition. Some of the possible treatment options are:

• Medication: There are medications that can improve nerve-muscle communication by either increasing the amount of acetylcholine or prolonging the effects of tensilon. These drugs usually have to be taken for life.
• Immunosuppressants: If the muscle weakness is caused by an autoimmune disease, drugs that suppress the immune system can help to reduce antibody production and protect the receptors on the muscle cells. However, these drugs also have side effects and must be dosed carefully.
• Thymectomy: This is an operation in which the thymus gland is removed. The thymus gland is an organ responsible for the maturation of immune cells. In some dogs with acquired myasthenia, a thymectomy can lead to an improvement or even a cure of the disease. The reasons for this are not yet fully understood.
• Symptomatic treatment: Other measures can also be taken to improve the dog's quality of life, such as an adapted diet, regular physiotherapy, avoidance of stress or heat or artificial respiration in the event of respiratory distress.