Non-inflammatory Hereditary Myotonia in Dogs
Non-inflammatory hereditary myotonia is a muscle disorder distinguished by sustained muscle contraction or delayed relaxation, particularly evident during movement. While it can be acquired later in life through factors such as herbicide ingestion, this discussion primarily focuses on congenital myotonia, frequently observed in chow chows and miniature schnauzers.
Symptoms and Types
The following symptoms are typically linked with non-inflammatory hereditary myotonia. They may ameliorate after exercise and/or exacerbate in cold conditions:
- Alteration in voice
- Muscle stiffness
- Respiratory difficulties
- Challenges in rising or moving
- Difficulty swallowing (dysphagia)
- Regurgitation, particularly post-meals
- Tongue protrusion from the mouth
Causes
The cause of this form of non-inflammatory myopathy is hereditary. It is passed down from either the mother or father who carry the same sarcolemmal defect, impacting the cell membrane of a muscle cell.
Diagnosis
To diagnose this condition, it is important to provide your veterinarian with a detailed history of your dog’s health, including when the symptoms began and their nature. Your veterinarian will then perform a comprehensive physical examination, along with conducting a biochemistry profile, urinalysis, and complete blood count (CBC). Elevated levels of creatine kinase enzymes may indicate dystrophin deficiency, while liver enzyme levels may also be elevated in affected dogs.
During the examination, your veterinarian will gently tap the surface of your dog’s tongue, both while conscious and under anesthesia. The sustained dimpling produced on the tongue’s surface can provide diagnostic clues. Additionally, a DNA-based test is available to identify affected and carrier miniature schnauzers for further confirmation of the diagnosis.
Treatment
While there isn’t a specific treatment regimen for non-inflammatory hereditary myotonia, certain medications such as procainamide, quinidine, phenytoin, and mexiletine can assist in reducing muscle stiffness and regurgitation. However, it’s important to note that these medications do not improve the abnormal gait linked with the disorder.
Living and Management
It’s advisable to discourage your dog from engaging in strenuous activities or exercises that could elevate its respiration, and to avoid exposure to cold temperatures, which may worsen the symptoms. Despite treatment, the prognosis for dogs with non-inflammatory hereditary myotonia remains very poor. Your veterinarian will also advise against breeding the dog to prevent the disease from progressing to future generations.
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