Quadrilateral Space Syndrome

Quadrilateral space syndrome (QSS) arises from compression or mechanical injury to the axillary nerve or the posterior circumflex humeral artery (PCHA) as they pass through the quadrilateral space (QS). Quadrilateral space syndrome is an uncommon cause of paresthesia and an underdiagnosed cause of digital ischemia in overhead athletes. Quadrilateral space syndrome can present with neurogenic symptoms (pain and weakness) secondary to axillary nerve compression. In addition, repeated abduction and external rotation of the arm is felt to lead to injury of the PCHA within the QSS. This often results in PCHA thrombosis and aneurysm formation, with distal emboli. Because of relative infrequency, QSS is rarely diagnosed on evaluation of athletes with such symptoms. We report on 9 patients who presented at Mayo Clinic with QSS. Differential diagnosis, a new classification system, and the management of QSS are discussed, with a comprehensive literature review. The following search terms were used on PubMed: axillary nerve, posterior circumflex humeral artery, quadrilateral space, and quadrangular space. Articles were selected if they described patients with symptoms from axillary nerve entrapment or PCHA thrombosis, or if related screening or imaging methods were assessed. References available within the obtained articles were also pursued. There was no date or language restriction for article inclusion; 5 studies in languages besides English were reported in German, French, Spanish, Turkish, and Chinese. a 2015 Mayo Foundation for Medical Education and Research n Mayo Clin Proc. 2015;nn(n):1-13 From the Department of Medicine (S.-A.N.B.), Department of Radiology (D.A.D.), Division of Vascular Medicine (C.J.B., W.E.W., I.R.M.), Division of Vascular Surgery (A.J., G.S.O., P.G.), and Division of Vascular and Interventional Radiology (H.B., I.R.M.), Mayo Clinic, Rochester, MN; and Division of Vascular and Interventional Radiology (S.G.N., E.A.H.) and Department of Orthopedic Surgery (K.J.R.), Mayo Clinic, Scottsdale, AZ. Q uadrilateral space syndrome (QSS) arises from compression or mechanical injury to the axillary nerve (neurogenic quadrilateral space syndrome [nQSS]) and/or posterior circumflex humeral artery (PCHA) (vascular quadrilateral space syndrome [vQSS]) as they pass through the quadrilateral space (QS). The QS is bounded by the edge of the long head of the triceps medially, the medial edge of the surgical neck of the humerus laterally, the tendon of the teres major and latissimus dorsi muscles inferiorly, and the teres minor muscle or the scapulohumeral capsule superiorly (Supplemental Figure 1, available online at http://www.mayoclinicproceedings.org). The term QSS was first coined by Cahill in 1980 and then again in 1983 in a subsequent article describing several patients with axillary Mayo Clin Proc. n XXX 2015;nn(n):1-13 n http://dx.doi.org/10.1016 www.mayoclinicproceedings.org n a 2015 Mayo Foundation for M nerve compression. McCarthy et al later reported partial occlusion of the PCHA in a baseball pitcher, with distal embolization to the right third digit, felt to be due to PCHA injury within the QS. Subsequently, QSS has been reported most commonly in overhead or “throwing” athletes in sports that heavily involve abduction and external rotation (AER), including volleyball, baseball, and swimming. Quadrilateral space syndrome has also been associated with other activities with frequent AER, such as yoga or window cleaning. Patients with QSS manifest with various symptoms (Figure 1). Neurogenic manifestations may include nondermatomal neuropathic pain, numbness, and weakness in the shoulder (usually posterior), often radiating down the arm. Vascular manifestations may /j.mayocp.2014.12.012 edical Education and Research 1