Subclinical myopathy associated with hyperadrenocorticism in the dog

Area of Science:

• Veterinary Neurology
• Canine Endocrinology
• Muscle and Nerve Pathology

Background:

• Hyperadrenocorticism (Cushing's disease) is a common endocrine disorder in dogs.
• Neuromuscular complications are not widely recognized but can significantly impact canine health.

Purpose of the Study:

• To investigate the presence and nature of neuromuscular disorders in dogs diagnosed with hyperadrenocorticism.
• To characterize the pathological changes in muscle and nerve tissues associated with this condition.

Main Methods:

• Clinical evaluation and diagnostic confirmation of hyperadrenocorticism using hormone level testing.
• Electromyography (EMG) to assess nerve and muscle electrical activity.
• Histopathological examination of muscle (biceps femoris) and nerve (peroneal) biopsies.

Main Results:

• One of seven dogs exhibited neuromuscular disorder signs alongside hyperadrenocorticism.
• EMG revealed abnormal high-frequency discharges in all dogs.
• Muscle biopsies showed degenerative changes, including atrophy, necrosis, ragged red fibers, and fiber splitting.
• Nerve biopsies indicated demyelination, onion-bulb formation, and axonal damage.

Conclusions:

• Findings suggest a glucocorticoid-induced myopathy in dogs with hyperadrenocorticism.
• A neurogenic component may also contribute to the observed neuromuscular dysfunction.
• Further research is warranted to elucidate the mechanisms and clinical implications.