Quadrilateral space syndrome
Weight-lifter with chronic pain in the right shoulder. No history of trauma.
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Transverse ultrasound scan over the muscle bellies at the inferior aspect of the infraspinal fossa of the scapula, demonstrating reduced volume and hyperecogenicity of the right teres minor muscle (TM), in comparison to the normal contralateral shoulder, consistent with muscle atrophy. The infraspinatus muscle is also partially seen (IS). No mass was seen in the quadrilateral space.
Quadrilateral space syndrome is due to compression of the axillary nerve in the quadrilateral space. In weight-lifters, muscle hypertrophy may narrow the quadrilateral space and induce nerve compression. Other possible cause for neuropathy in this patient is nerve stretching from chronic overuse.
The axillary nerve innervates the teres minor and deltoid muscles and also gives a sensory branch to the deltoid region. Pain in the deltoid region and selective denervation of the teres minor are the most common presentations of the syndrome. In chronic cases the denervation leads to fatty infiltration and reduced muscle volume, as shown in this case.