Identification of a Musculus Levator Claviculae on Physical Exam: A Case Report and Literature Review

<b>Background and Clinical Significance</b>: The levator claviculae muscle (also known as cleidocervicalis) is a vestigial muscle located in the posterior triangle of the neck, extending from the upper cervical transverse processus to the clavicle. It has been detected in ~2% of humans, but is rarely documented in the radiologic or anatomic literature. When found on physical exam, it is usually mis-identified as lymphadenopathy, metastasis, cysts, an aneurysm, or other masses. It has been implicated in a few cases of thoracic outlet syndrome. <b>Case Presentation</b>: Herein, we describe a 25-year-old man with a weightlifting history, who was found to have a right levator claviculae muscle in the setting of unilateral mixed neurovascular thoracic outlet syndrome. The patient presented with right-sided extremity paresthesias, pain in the neck, shoulder, and arm, and symptom exacerbation with overhead activities. He also described intermittent unilateral pulsatile tinnitus during strenuous exercise. On physical exam, he was found to have a right carotid bruit, unequal systolic blood pressures, and positive Roos and Adson's testing. The variant muscle was identified with a modified exam maneuver, and was further characterized with sonography and MRI. Symptoms were managed with activity restriction and NSAIDs. We reviewed 17 cases of levator claviculae variant muscles in patients. <b>Conclusions</b>: The presence of levator claviculae muscles has been detected in patients with thoracic outlet syndrome, but never in a patient with an audible bruit and pulsatile tinnitus. This physical exam maneuver, used in conjunction with multimodal imaging, successfully aided diagnosis and direct medical management in this case.