LESSON OF THE MONTH

An unusual cause of shoulder pain

P Wong, J V Bertouch, G A C Murrell, M Hersch, P P Youssef

A 20 year old man with no significant pastmedical problems presented with a six weekhistory of gradual onset diVuse left shoulderand scapula pain. Two weeks before the onsetof pain he had started work as a builder,performing heavy lifting. There was no historyof injury or other precipitant. In the weekbefore presenting, the severity of the pain pre-vented him from working despite regular anal-gesia. He did not complain of upper limbweakness. No constitutional symptoms werepresent. There was no preceding viral-likeillness or vaccination.

On examination, there was left infraspinatustenderness and wasting (see fig 1) withweakness of external rotation of the shoulder.Power in other muscle groups around the leftshoulder was normal. All upper limb reflexeswere present and sensation was normal.Examination of the left axilla revealed fivesmall mobile lymph nodes. There was no otherlymphadenopathy or splenomegaly.

Computed tomography (CT) of the leftscapula and axilla was performed to determineif significant lymphadenopathy was present, forexample, because of lymphomatous involve-ment. It showed wasting of the musclessurrounding the scapula but no mass lesions inthe region of the brachial plexus. There werenon-enlarged lymph nodes in the axilla.

Electromyographic (EMG) assessment re-vealed profuse fibrillations and positive sharpwaves in the left infraspinatus muscle but nounits under voluntary control, consistent with

active denervation. The left supraspinatus,biceps, triceps and deltoid were normal. Mag-netic resonance imaging (MRI) of the leftshoulder region confirmed a 2 cm by 1 cmmulti-loculated fluid collection at the spinogle-noid notch causing compression of the inferiorbranch of the suprascapular nerve that suppliesinfraspinatus (figs 2 and 3). There was no evi-dence of more proximal compression of thesuprascapular nerve. A small tear of theposterosuperior glenoid labrum was also iden-tified.

A provisional diagnosis of a ganglion wasmade and the patient was referred to an ortho-

Figure 1 Left infraspinatus wasting. (View from behind the patient).

Figure 2 Axial (T2 weighted) MRI showing the ganglioncyst in the spinoglenoid notch adjacent to the glenoidlabrum.

Figure 3 Diagram showing a ganglion in the spinoglenoidnotch causing compression of the nerve to infraspinatus.

Ganglion cyst

Suprascapular nerve

Ann Rheum Dis 1999;58:264–265264

Prince of WalesHospital, Sydney, NewSouth Wales, AustraliaP WongJ V BertouchP P Youssef

St George Hospital,Sydney, New SouthWales, AustraliaG A C MurrellM Hersch

Correspondence to:Dr P Youssef, Royal PrinceAlfred Medical Centre, Suite408, 100 Carillon Avenue,Newtown, Sydney, NewSouth Wales, Australia 2042.

Accepted for publication18 January 1999

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paedic surgeon for an arthroscopic gangliondrainage and repair of the glenoid labrum. Thiswas successfully performed. Ten weeks afterthe operation, there was significant reductionin both shoulder pain and infraspinatus wastingwith only a mild reduction in global range ofmovement. Unfortunately, the patient failed topresent for a follow up MRI three months laterto assess if there had been a recurrence of theganglion.

DiscussionWith the advent of MRI, suprascapular nervecompression is becoming increasingly recog-nised as a cause of shoulder pain in theorthopaedic,1–4 radiological,5 6 and sportsmedicine8 literature. However, we are unawareof any such reports in the rheumatologicalliterature.

The suprascapular nerve arises from theupper trunk of the brachial plexus. It thentraverses the suprascapular notch underneaththe transverse scapular ligament. On enteringthe supraspinatus fossa, it innervates thesupraspinatus muscle. It then enters the infra-spinatus fossa via the spinoglenoid notch toinnervate the infraspinatus muscle (fig 3).1 Inthis patient, the ganglion was located at thespinoglenoid notch, causing only compressionof the nerve to infraspinatus resulting in weak-ness of the infraspinatus muscle.

This patient is noteworthy because of hisrelatively acute presentation. The usual pre-senting symptom is that of longstanding, deepand diVuse posterolateral shoulder pain. How-ever, this man presented with pain of only sev-eral weeks’ duration that had worsened over thepreceding week, raising the possibility ofbrachial neuritis.

This case demonstrates that EMG and nerveconduction studies are useful in localising thesite of nerve compression. They distinguishnerve entrapment at the suprascapular notch,which produces denervation of both suprasp-inatus and infraspinatus, from that at thespinoglenoid notch, which results in infrasp-inatus weakness only. In addition, they excludemore widespread pathology, for example bra-chial neuritis.

Nevertheless, MRI is the imaging modalityof choice for defining the lesion because of itsexcellent resolution of soft tissue. In this case, itwould have been preferable to perform MRI asthe initial investigation, thereby negating theneed for EMG and nerve conduction studies.However, MRI is not readily available in ourunit. Hence, this patient had initial EMG andnerve conduction studies to delineate the neu-rological abnormality.

This case also demonstrates many of thetypical features of this condition. It is mostlyseen in men for two reasons. Firstly, there is anassociation with weight lifting.4 7 Secondly, thespinoglenoid ligament is absent in 50% ofwomen compared with 13% of men.9

The pathogenesis of this condition is uncer-tain. It is believed that trauma results in tearingof the posterior capsulo-labral complex. Thisallows synovial fluid to leak out of the joint

along the path of least resistance, thus resultingin a ganglion cyst.1 Tirman et al6 have shown anassociation between ganglion cysts and glenoidlabrocapsular tears on MRI—as seen in thispatient. They suggest that detection of a shoul-der ganglion cyst should prompt both a clinicaland MRI evaluation of the glenoid labrum andjoint capsule.

The treatment of this condition is dependentupon the extent of pain and the loss offunction. In the absence of pain, shoulderrehabilitation to maximise function is usuallythe only intervention necessary, as the func-tional deficit is usually mild.1 However, in thepresence of persistent or severe pain, as in thiscase, surgery is required. Arthroscopic evalua-tion is often necessary with simultaneous repairof intra-articular pathology to prevent a recur-rence of the ganglion. Traditionally, open gan-glion excision is performed. However, Iannottiand Ramsey2 report a series of three cases inwhich suprascapular nerve compression by aganglion cyst was treated by arthroscopicdecompression of the cyst into the shoulderjoint. In each of their three cases, the patient’ssymptoms resolved and a postoperative MRIshowed no reaccumulaton of the fluid in theganglion. The procedure was well tolerated.Successful ultrasound or CT guided aspirationof ganglia causing suprascapular nerve com-pression has also been reported.4

Overall, in patients with previously normalshoulder anatomy, a successful surgical proce-dure involving decompression of the ganglionwith repair of any underlying labral pathologyresults in a good long term prognosis.

The lessonsx Suprascapular nerve entrapment must be

considered in the diVerential diagnosis of apainful shoulder, particularly in the presenceof supraspinatus or infraspinatus weakness.

x The most appropriate investigation is MRIof the shoulder girdle. However, EMG andnerve conduction studies can be useful indetermining the site of nerve compressionand the degree of nerve dysfunction.

1 Fehrman DA, Orwin JF, Jennings RM. Suprascapular nerveentrapment by ganglion cysts: A report of six cases witharthroscopic findings and review of the literature. Arthros-copy 1995;11:727–34.

2 Iannotti JP, Ramsey ML. Arthroscopic decompression of aganglion cyst causing suprascapular nerve compression.Arthroscopy 1996;12:739–45.

3 Ogino T, Minami A, Kato H, Hara R, Suzuki K.Entrapment neuropathy of the suprascapular nerve by aganglion. J Bone Joint Surg Am 1991;73:141–7.

4 Ganzhorn RW, Hocker JT, Horowitz M, Switzer HE.Suprascapular nerve entrapment. J Bone Joint Surg Am1981;63:492–4.

5 Fritz RC, Helms CA, Steinbach LS, Genant HK. Supras-capular nerve entrapment: Evaluation with MR imaging.Radiology 1992;182:437–44.

6 Tirman PFJ, Feller JF, Janzen DL, Peterfry CG, BergmanAG. Association of glenoid labral cysts with labral tears andgleno-humeral instability: Radiologic findings and clinicalsignificance. Radiology 1994;190:653–8.

7 Neviaser TJ, Ain BR, Neviaser RJ. Suprascapular nervedenervation secondary to attenuation by a ganglion cyst. JBone Joint Surg Am 1986;68:627–8.

8 Ferrick MR, Marzo JM. Ganglion cyst of the shoulder asso-ciated with a glenoid labral tear and symptomaticglenohumeral instability. Am J Sports Med 1997;25:717–19.

9 Kaspi A, Yanai J, Pick CG, Mann G. Entrapment of the dis-tal suprascapular nerve. Int Orthop 1988;12:273–5.

An unusual cause of shoulder pain 265

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ay 1999. Dow

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