Pec Muscle Atrophy: Identify the Source of Weakness

When evaluating a patient with shoulder or neck pain, it is important to consider all of the structures that may contribute to their current symptoms. These structures include local muscles, peripheral or central nervous system dysfunction, soft tissue stabilizing structures, among others. Next, use this information in combination with other portions of the subjective history (mechanism of injury, description of symptoms, and pattern of symptoms) to identify the one or two primary causes of the problem.

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No recent injury, shoulder or neck pain, but still muscle atrophy...

In this particular case, the patient denied any recent mechanism of injury, denied shoulder pain, and also did not report any neck pain.

​At this point of the subjective history, I was still considering the cervical spine, thoracic outlet region, pectoral muscle strain, and other nervous system dysfunction as all possible causes of the patient's muscle atrophy.

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Look Beyond the Local Muscle Atrophy

Since muscle atrophy was present (without signs of a single muscle trauma or strain), it is important to investigate other muscles with the same segmental and peripheral nerve contributions. This will determine if the weakness is localized or present in multiple muscle groups. Below I review the pectoralis muscle with a special emphasis on the sternocostal fibers. 

Later in the evaluation, the patient remembered that his biceps brachii and pectoral muscle strength had gradually decreased on his right (involved side) versus his left over the past few months while strength training.  

This statement is very important because it most likely ruled out a muscle strain, and ruled in nervous system dysfunction. Further physical examination helped rule out red flags for cervical myelopathy. Additionally, muscle strength testing found weakness in other C5, C6, and C7 muscles. At this point, I concluded that he was safe for treatment, but needed regular reassessment to ensure no further progression of neurological symptoms. 

To learn more about the outcome of this patient, watch the video below!
(this video is taken from our insider access library)

Find more cases like this in TSPT insider access!

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