Ultrasound findings of teres minor denervation in suspected quadrilateral space syndrome

Abstract

Isolated teres minor denervation is an uncommon finding on sonographic examination. We present a case of a 64-year-old man with increased echogenity of the teres minor muscle and a slight reduction in muscle bulk. Investigation of a suspected axillary nerve lesion included a detailed sonographic examination of the posterior shoulder and the axillary space, followed by MR imaging and electrophysiologic testing. This case demonstrates the potential importance of examining rotator cuff muscles when performing sonographic examination of the shoulder in patients with persistent symptoms, no history of trauma, and absence of tendon tears.

Quadrilateral Space Syndrome

“…Patients with muscle atrophy occurring from nQSS present with paresis, paresthesia, poorly localized shoulder pain, 2 or tenderness with palpation of the anterior, 26,51 lateral, 60 or most often posterior 27 shoulder (over the QS 2 ), corresponding to deltoid and teres minor muscle fibers (Figure 1). There is often radiation of paresthesias to the arm or the forearm in a nondermatomal distribution.…”

“…Various fixed anatomic anomalies can lead to nQSS, with fibrous bands being the most common. 2,5,23,32,[46][47][48][49][50][51] In cadaveric shoulder dissections, fibrous bands were located between the teres major and the long head of the triceps; external rotation reduced the cross-sectional area of the QS. 2 The fibrous band often results from overt or occult repeated microtrauma to connective tissue in the QS with the formation of permanent scarring and adhesions.…”

“…This suggests possibly a 2:1 prevalence of nQSS relative to vQSS. The Table catalogs a larger distribution of published nQSS [3][4][5]17,18,23,24,26,32,[46][47][48][49][50][51][54][55][56][57]60,62 and vQSS [6][7][8][9][10][11][12][13][14][15]21,22,25,28,34,41,42 cases. Results from the Table support a 1.5:1 prevalence of nQSS relative to vQSS, with a male predominance (male/female ratio, 7:1) for all QSS, and an almost exclusive male population for vQSS (likely due to traditional sex distribution in overhead athletics).…”

Clinical outcomes after decompression of the nerve to the teres minor in patients with idiopathic isolated teres minor fatty atrophy

“…Isolated teres minor atrophy is a recently described and potentially important clinical entity 1 . The main clinical presentation includes: posterior shoulder pain, weakness of abducted external rotation (hornblower’s position), isolated teres minor atrophy on MRI or ultrasonography, and/or isolated teres minor involvement on EMG 4 .…”

“…Fibrous bands in the quadrilateral space have been suggested as an etiology of isolated teres minor atrophy 1; 10 . An anatomical study by Chafik et al 3 described two variants of fascial anatomy in the teres minor: 11/23 specimens had an individual fascial compartment enveloping the teres minor and 12 specimens had no circumferential individual compartment.…”