Hi, everyone. My name is Kaylee Gemark, and I'm presenting a case report of bilateral medial pectoral nerve palsy in a weightlifter, which is a rarely reported finding that results in medial pectoral atrophy and weakness. As a brief anatomy review, from the medial cord of the brachial plexus, the medial pectoral nerve, which I may refer to as the MPN, innervates the pec minor and the inferior sternal pec major. The MPN reaches the pec major after either passing through the pec minor, which is reported to be the case in 62% to 75% of individuals, or by passing around the lateral aspect of the pec minor in a reported 25% to 38% of individuals. One proposed mechanism of medial pectoral nerve palsy in weightlifters is intramuscular compression of the MPN within the hypertrophied pec minor muscle. The idea here is that as the pec minor hypertrophies with weightlifting, the MPN becomes compressed during its intramuscular course. You can see a representation of the course of the MPN on its way to pec major in the figure on the left-hand side of the poster. As you can see, the lateral pectoral nerve does not have an intramuscular course through the pec minor. In this case, our patient is a 27-year-old male who presented with atraumatic right pec weakness and atrophy. He initially had onset of these symptoms about six years prior to presentation when he was a competitive rower and involved in an intensive weightlifting regimen without a known traumatic injury at the time. He noted subjective weakness during push-ups and dips. A few months prior to presentation with us, while engaged in intensive firefighter training and a weightlifting regimen, he began to notice new left medial pectoral atrophy in addition to his symptoms on the right. On presentation, his exam was significant for bilateral medial pec atrophy and diminished volitional activation. His exam was otherwise unremarkable. His workup included MRI of his shoulder, chest, and his C-spine. These studies were unremarkable aside from fatty atrophy of the right medial pec major. He then underwent extensive bilateral upper extremity nerve conduction studies in needle EMG. EMG was consistent with right greater than left medial pectoral mononeuropathies with evidence of positive sharp waves and fibrillation potentials. As you can see from the figure in the central portion of the poster, all other portions of the tested brachial plexus were normal, suggesting that cervical radiculopathy or brachial plexopathy was unlikely. Brachial motor recruitment in the right upper sternal head suggested poor prognosis for spontaneous recovery. And central recruitment in the left upper and lower sternal head suggested a fair prognosis for spontaneous recovery. The patient was referred to orthopedic surgery for consideration of surgical intervention, including exploration of the MPN and neuralysis if a site of compression could be found. He ultimately was lost to follow-up and did not undergo a surgery as far as we know. In summary, this was the interesting case of a weightlifter who presented with atraumatic bilateral medial pectoral atrophy and weakness. He was found to have isolated bilateral medial pectoral nerve palsies with otherwise unremarkable EMG and imaging findings. His presentation was likely secondary to intramuscular compression of the MPN within the hypertrophied pec minor muscle in the setting of intensive weightlifting, which has been previously reported in this population. Rapid muscle hypertrophy in the setting of weightlifting can predispose individuals to this injury, as the MPN can become compressed during its intramuscular course through the pec minor. Compression of a weightlifting regimen can then exacerbate this entrapment. Early recognition and prompt electrodiagnosis of intramuscular pec nerve entrapment in weightlifters is important for a couple of reasons. Number one is to guide recommendations for activity modification, two, to expedite referral for consideration of surgical intervention, and three, to maximize potential for nerve recovery. Thank you so much for your time and attention, and thanks to Dr. Aaron Bunnell for his expertise on this interesting case.

Kaylee Gemark

bilateral medial pectoral nerve palsy

atrophy

weakness

weightlifter