Hourglass-like constriction of the suprascapular nerve: a contraindication for minimally invasive surgery

Abstract

Suprascapular nerve (SSN) entrapment is usually ascribed to static or dynamic compression. When no cause of compression is found, SSN entrapment is defined as idiopathic. Focal hourglass-like constriction (H-LC) of the SSN that results in muscle paralysis represents an unusual condition that may be misinterpreted and erroneously diagnosed as SSN entrapment or as neuralgic amyotrophy. With the aim of finding clinical and surgical clues that could differentiate the traditional form of idiopathic SSN entrapment from the rare H-LC, a series of 6 cases of SSN palsy caused by H-LC is presented. All but 1 supraspinatus muscle recovered M5 muscle strength. The Constant shoulder score was excellent in 3 patients, good in 1, fair in 1, and poor in 1. If a diagnosis is not made in time, H-LC may evolve from mild to severe nerve torsion that may require a shift in surgical procedure from epineurotomy and external neurolysis to focal resection and suture. If an incorrect therapy is chosen, the chance of recovery might be definitively compromised with the persistence of muscle palsy. Conversely, when SSN palsy persists despite notch decompression, especially when it is performed with a limited open approach or arthroscopically, concerns about the real etiology and location of nerve compression responsible for the nerve palsy may arise. When approaching SSN pathology, H-LC should be considered as a potential cause of nerve palsy, as it may represent a contraindication for a limited open approach or arthroscopic decompression.