Schwannoma del nervio supraescapular: Informe de un caso.(Inglés)

aDepartment of Orthopaedic Surgery, University of Pennsylvania School of Medicine, Philadelphia, PA, USA cDivision of Hand Surgery, Hospital of the University of Pennsylvania, University of Pennsylvania School of Medicine, Philadelphia, PA, USA bDepartment of Orthopaedic Surgery, University of California Davis School of Medicine, Sacramento, CA, USA The suprascapular nerve enters the supraspinatus fossa through the suprascapular notch before passing through the spinoglenoid notch and entering the infraspinatus fossa. Entrapment of the suprascapular nerve under the transverse scapular ligament and the spinoglenoid ligament has been well documented in the literature.1 and 7 In addition, suprascapular nerve compression has been reported as a result of posterior labral tears, glenoid cysts, or repeated traction in throwing athletes.3 and 6

We report the case of a 30-year-old woman with a 1-year history of right shoulder pain and weakness consistent with suprascapular nerve compression. Imaging revealed a solid mass within the suprascapular notch, and a biopsy confirmed the diagnosis of a benign schwannoma of the suprascapular nerve.

Case report A 30-year-old woman presented with a 1-year history of worsening right shoulder pain radiating down the arm. She also had weakness with activities of daily living but had no complaints of numbness or paresthesias.

The patient had no history of trauma and stated that her symptoms started insidiously. Her past medical history was significant for multiple excisions of benign schwannomas in the external ear and temporal region. A full medical workup did not reveal any of the other diagnostic criteria for neurofibromatosis 1 or 2. The patient initially presented to an orthopaedic surgeon who diagnosed her with subacromial impingement based on her clinical history and physical examination. She underwent an arthroscopic evaluation and subacromial decompression without relief of her symptoms. Because of continued symptoms of rotator cuff weakness and pain after the arthroscopic procedure, she was referred to our service for further assessment.

On physical examination, there was mild atrophy of the right infraspinatus and supraspinatus compared with the left. A small tender mass was palpable under the trapezius at the midclavicle level. Pressure in this area produced severe pain in the shoulder region radiating down to the arm. The patient had full, symmetric range of motion in forward elevation and internal and external rotation. Neurovascular examination revealed slight weakness on external rotation with the arm at the side and with the arm at 90° of abduction. Strength of internal rotation was normal in both positions. There was no evidence of subacromial impingement, and biceps-provocative maneuvers were negative. There were no skin lesions or other soft-tissue masses detected on examination.

The patient presented with plain radiographs and a magnetic resonance image of the right shoulder obtained after the initial subacromial decompression. The plain radiographs did not reveal any bony pathology, and magnetic resonance imaging (MRI) identified a well-circumscribed lesion in the suprascapular notch, non-enhancing on T1 sequences but enhancing on T2. Magnetic resonance images with gadolinium contrast revealed a mass in the suprascapular notch with contrast enhancement and a central area of necrosis, suggestive of a solid tumor rather than a cystic lesion. The patient underwent an open excisional biopsy of the lesion through a trapezius-splitting approach. At the time of surgery, a well-defined, solid mass within the sheath of the suprascapular nerve was identified. The mass was shelled out from the nerve parenchyma allowing preservation of axons within the epineurium. Gross inspection by the pathologist showed a shiny white-yellow mass with a central degenerative cyst. Histologic sections showed Antoni A and Antoni B areas as well as Verocay bodies with palisading cells, characteristic of benign schwannomas. Postoperatively, the patient reported complete resolution of her symptoms without deficits in the suprascapular nerve distribution. At 2-year follow-up, she had no pain and full strength in her rotator cuff musculature. She returned to her premorbid functional status. Functional assessment with the Disabilities of the Arm, Shoulder and Hand questionnaire revealed a score of 0, suggesting no functional disability.

Discussion Suprascapular neuropathy may occur as a result of direct trauma, repetitive motion, or compression from neighboring lesions. Compression of the nerve can occur at either the suprascapular notch or the spinoglenoid notch. Although traction injuries are more common at the suprascapular notch, where the transverse scapular ligament tethers the nerve, extrinsic compression is most often seen at the spinoglenoid notch.7 Suprascapular nerve entrapment should be considered in the differential diagnosis of poorly defined shoulder pain with weakness of abduction and external rotation.

Ganglion cysts arising from labral tears are the most common source of extrinsic suprascapular nerve compression.9 These cysts are usually identified by MRI as homogenous, low–signal intensity lesions on T1-weighted images and high–signal intensity on T2-weighted images.4 The addition of gadolinium results in rim enhancement without contrast uptake in the cavitary region of the cyst.

A review of the literature identified few reports of extrinsic suprascapular neuropathy by lesions other than ganglion cysts. Hazrati et al5 documented nerve compression at the suprascapular notch by a lipoma, and Faridah and Abdullah2 reported a case of suprascapular neuropathy in a patient with non-Hodgkin’s lymphoma. In a review of 27 masses adjacent to the suprascapular nerve described on MRI, Fritz et al4 identified 21 ganglion cysts, 2 synovial cell sarcomas, 1 Ewing’s sarcoma, 1 chondrosarcoma, 1 metastatic renal cell carcinoma, and 1 fracture hematoma. We identified one other report of a suprascapular nerve schwannoma leading to compression symptoms. Sharma et al8 described a patient with a 5-cm mass in the area of the suprascapular notch, initially identified by computed tomography scan and diagnosed as a schwannoma after excisional biopsy.

Our patient had a diagnosis of schwannomatosis, a form of neurofibromatosis in which patients have multiple schwannomas on the cranial, spinal, and peripheral nerves but do not have vestibular tumors or go deaf. This report represents the second documented case of suprascapular nerve entrapment from a benign schwannoma. Although ganglion cysts are more common sources of nerve entrapment, a thorough workup is necessary to rule out other, rare causes of compression from extrinsic masses, particularly in patients with a history of neoplastic lesions. MRI is the modality of choice to detect and delineate these lesions, and gadolinium may be a useful adjunct in differentiating solid masses from the more common cystic lesions. Suprascapular neuropathy as a result of solid, space-occupying lesions is usually treated with an open excisional biopsy. Benign schwannomas are typically shelled out of the nerve parenchyma, leading to nerve decompression without compromise of nerve function.

In conclusion, schwannomas are rare causes of suprascapular nerve entrapment at the suprascapular notch. Evaluation of masses in this area by use of MRI with gadolinium is valuable in distinguishing solid lesions from the more common ganglion cysts. With careful surgical excision, patients can expect symptom resolution and restoration of shoulder function.