Muscle atrophy describes the thinning or wasting of muscles. It is a common symptom in dogs, seen as part of many conditions.
- The causes of muscle atrophy are numerous but fall broadly into two categories: loss of nerve function or reduced muscle usage
- Disuse atrophy is the most common form, as is usually associated with conditions such as joint disease and forms of arthritis
- Neural atrophy is less common and occurs in conditions such as spinal injury or myasthenia gravis
- Investigation into the cause of muscle atrophy involves physical examination, blood work, urine samples, and diagnostic imaging such as X-rays, CT or MRI scans
- Treatment options vary depending on the identified disease process, but normally involve pain relief and anti-inflammatory medication, alongside medical or surgical treatment of the specific disease
- Prognosis varies similarly
A closer look: Muscle atrophy in dogs
Muscle atrophy varies significantly depending on the underlying trigger.
Disuse atrophy occurs when a muscle is no longer being used, and is usually mild and slowly progressive. This form of atrophy is often associated with spinal, joint or muscle disorders such as hip dysplasia, osteoarthritis, or chronic intervertebral disc disease, where pain during movement discourages use of the muscle.
Neural atrophy occurs when the muscles lose nerve supply, either permanently, or temporarily, and occurs in conditions such as polyneuropathies, polyradiculoneuritis, or traumatic injury to nerves. Cases of neural atrophy result in rapid, severe muscle loss which is sometimes reversible, but is often permanent.
Dogs with mild, slowly progressive loss of muscle mass benefit from prompt veterinary attention. Dogs with sudden onset, severe muscle atrophy require emergency treatment, as sudden onset is typically associated with more severe conditions.
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Possible causes
Muscle atrophy is also expected as part of normal aging in geriatric dogs.
Risk factors
Muscle atrophy is common in dogs, and varies significantly in terms of the underlying disease process, severity, and prognosis.
Metabolic diseases such as Cushing's disease or hypothyroidism result in muscle atrophy as a result of increased breakdown of muscle proteins as part of the underlying condition. This muscle breakdown is usually slowly progressive, and moderate to severe.
Most muscle atrophy involves the postural muscles such the legs and spine. There are some conditions which result in atrophy of specific muscle groups, such as masticatory muscle myositis, which affects the chewing muscles specifically.
Testing and diagnosis
Investigation of muscle atrophy involves:
- Physical examination
- Routine blood work
- Urine sampling
- Nerve or muscle biopsies
- Electromyography
- Tensilon test
- Diagnostic imaging, including X-rays, CT scan or MRI scan
Treatment options depend on the underlying condition, but often involves medication such as:
- Pain relief
- Anti-inflammatories
- Corticosteroids
- Antibiotics
- Antiparasitic medications
Surgical treatment is appropriate in some cases, such as joint disease or compression of spinal cord.
Some cases benefit from conservative management including:
- Weight loss
- Exercise management
- Hydrotherapy or physiotherapy
- Joint supplements
