Pectoralis Minor Syndrome
Pectoralis minor syndrome (PMS) is a subset of neurogenic thoracic outlet syndrome (TOS) that can cause upper extremity symptoms of pain, paresthesia, and/or weakness due to compression of the neurovascular bundle by the pectoralis minor muscle (PM). The
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Richard J. Sanders
Abstract
Pectoralis minor syndrome (PMS) is a subset of neurogenic thoracic outlet syndrome (TOS) that can cause upper extremity symptoms of pain, paresthesia, and/or weakness due to compression of the neurovascular bundle by the pectoralis minor muscle (PM). The most distinguishing symptoms and signs of PMS include pain and/or tenderness in the subclavicular anterior chest wall and axilla. The clinical diagnosis of PMS can be confirmed by an improvement in symptoms and physical findings following a PM muscle block with local anesthetic. Treatment begins with PM stretching exercises. If this is insufficient, PM tenotomy (PMT) is a low risk operation, which can be performed as an outpatient. When PMS is the only diagnosis the success rate of PMT is 90 %, but when PMS is accompanied by nerve compression at the level of the scalene triangle the success rate of isolated PMT is only 35 %. PMS should also be considered in all patients with recurrent neurogenic TOS, as this condition has been found in a substantial proportion of such patients.
Introduction Pectoralis minor syndrome (PMS) is a subset of neurogenic thoracic outlet syndrome (TOS) that can cause upper extremity symptoms of paresthesias, pain, and/or weakness due to compression of the neurovascular bundle by the pectoralis minor muscle (PM) [1]. PMS may exist as an isolated condition or in combination with brachial
R.J. Sanders, MD Department of Surgery, HealthONE Presbyterian-St. Lukes Hospital, 4545 E. 9th Ave, #240, Denver, CO 80220, USA e-mail: [email protected]
plexus compression at the level of the supraclavicular scalene triangle (PMS + ST). Rarely, PMS may occur with predominant compression of vascular structures [2].
Anatomy The PM muscle arises from the anterior surfaces of ribs 2, 3, 4, and 5 and it inserts on the coracoid process of the scapula (see Chaps. 3 and 6). The space deep to the PM muscle contains the axillary artery (usually the most cephalad), the axillary vein (caudal to the artery), and the nerves of the brachial plexus, which are found around the
K.A. Illig et al. (eds.), Thoracic Outlet Syndrome, DOI 10.1007/978-1-4471-4366-6_15, © Springer-Verlag London 2013
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R.J. Sanders
94 Table 15.1 Etiology of isolated pectoralis minor syndrome
Etiology Auto accidents or non-work causes of neck trauma Falls on the floor, ice, etc. Work accidents and repetitive stress injury (RSI) Sports: weight lifting, swimming, baseball, tennis Spontaneous (Idiopathic) Total
# of patients 15 3 7 7 7 39
Percent (%) 38 8 18 18 18 100
Adapted from Sanders and Rao [1], p. 701–8. With permission from Elsevier
artery and between the artery and vein. The latassimus dorsi and subscapularis muscles lie deep to the neurovascular structures. Perhaps because the brachial plexus nerves are usually the most superficial structures, lying closest to the PM tendon, these nerves are most often involved in extrinsic compression.
Etiology In a recently published study of patients with PMS, either in isolation or accompanied by neuroge
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