Clinical Significance of Intramuscular Cysts in the Rotator Cuff and Their Relationship to Full- and Partial- Thickness Rotator Cuff Tears

Musculoskeletal Imaging Original Research Manvar et al. Cysts in the Rotator Cuff Musculoskeletal Imaging Original Research Ankur M. Manvar 1 Ajay Kamireddi 2 Sheetal M. Bhalani 2 Nancy M. Major 1,2,3 Manvar AM, Kamireddi A, Bhalani SM, Major NM Keywords: intramuscular cyst, MRI, rotator cuff tear, shoulder DOI:10.2214/AJR.07.3727 Received January 15, 2008; accepted after revision September 30, 2008. 1 Duke University, Erwin Rd., Durham, NC 27710. Address correspondence to A. M. Manvar (amm27@duke.edu). 2 Duke University School of Medicine, Durham, NC. 3 Department of Radiology, Duke University Medical Center, Durham, NC. AJR 2009; 192:719 724 0361 803X/09/1923 719 American Roentgen Ray Society Clinical Significance of Intramuscular Cysts in the Rotator Cuff and Their Relationship to Full- and Partial- Thickness Rotator Cuff Tears OBJECTIVE. Secondary signs have been sought to help in the MR diagnosis of rotator cuff tears, especially partial-thickness tears. We sought to determine whether intramuscular cysts are always present with rotator cuff tears and the types of rotator cuff tears with which they present, and to establish the clinical significance of finding intramuscular cysts. MATERIALS AND METHODS. Retrospective analysis of our institution s database of 5,101 MRI examinations of the shoulder during an 8-year period resulted in 187 examinations in 185 patients who were thought to have intramuscular cysts. Of the 187 examinations, 134 shoulders in 132 patients (62 women, 70 men) met our criteria for an intramuscular cyst. RESULTS. Of the 134 shoulders with intramuscular cysts, 102 (76.1%) showed imaging findings of both intramuscular cysts and rotator cuff tears. Thirty-two of the 134 (23.9%) shoulders were diagnosed with only an intramuscular cyst and were not associated with a rotator cuff tear. Fifty-five of 102 (53.9%) shoulders consisted of an intramuscular cyst associated with a full-thickness rotator cuff tear, and 47 of 102 (46.1%) shoulders presented with a partial-thickness rotator cuff tear. Forty-eight of 102 (47.1%) shoulders with both an intramuscular cyst and a rotator cuff tear also underwent the reference standard arthroscopy examination to confirm the MRI findings. In 46 of 48 (95.8%) shoulders that underwent arthroscopy, the findings confirmed the imaging evidence; the other two cases were shown to have an intact rotator cuff at arthroscopy. CONCLUSION. Our study echoes the findings of previous studies that suggest a relationship between intramuscular cysts and full- and partial-thickness rotator cuff tears but illustrates that the incidence of an isolated intramuscular cyst is higher than previously expected. When intramuscular cysts present with rotator cuff tears, they present with full- and partial-thickness rotator cuff tears in relatively equal proportions. The presence of an intramuscular cyst on MRI, although it may be an isolated finding, should prompt a thorough search of all the rotator cuff tendons for tears so that the patient may receive appropriate follow-up. G iven the variations in reported sensitivities in detecting partialthickness rotator cuff tears with MRI, many studies have sought secondary signs to help in the diagnosis of rotator cuff disorders, especially partialthickness rotator cuff tears [1 3]. A secondary sign that will be explored in this article is the correlation of intramuscular cysts with rotator cuff abnormalities of both full- and partial-thickness tears. Previous studies have shown an association between intramuscular cysts and full-thickness and partial-thickness rotator cuff tears. A study by Sanders et al. [4] showed, among a sample size of 13 patients who presented with intramuscular cysts on MRI, that all had either full- or partial-thickness rotator cuff tears. Five of the 13 patients underwent follow-up arthroscopy of the shoulder, and in all five, a rotator cuff abnormality was confirmed [4]. In that study, six of the 13 (46%) cases involved full-thickness rotator cuff tendon tears, and seven (54%) involved partial-thickness tears. A larger study by Kassarjian et al. [5] showed that 31 of 32 patients with intramuscular cysts evident on MRI examination of the shoulder had either full- or partial-thickness rotator cuff tears. Eleven of the 32 patients underwent follow-up arthroscopy of the shoulder, and in all 11 cases MRI findings correlated with arthroscopic findings [5]. In that study, 16 of 32 (50%) cases with intramuscular cysts had partial-thickness rotator cuff tears, and 15 of 32 (47%) had full-thickness rotator cuff tears [5]. The significance of these AJR:192, March 2009 719

Manvar et al. studies is that they indicate a strong association between intramuscular cysts and rotator cuff disorders. A full-thickness rotator cuff tear is defined as a tear that extends from the articular surface to the bursal surface of one of the rotator cuff muscles. A partial-thickness rotator cuff tear is defined as a tear that involves only one surface (either articular or bursal) of the rotator cuff muscles. Intramuscular cysts have been defined as unilocular or multilocular rounded fluid collections that are located in the sheath or substance of one or more of the rotator cuff muscles but do not extend to either the articular or bursal surface [5]. Intramuscular cysts are rarely palpable on physical examination and often are not visible on arthroscopic examination. The purpose of our study was to determine whether intramuscular cysts by MRI criteria are reliable secondary signs of rotator cuff tears; whether the presence of intramuscular cysts tends to favor the presence of either a partial- or a full-thickness rotator cuff tear; and whether an intramuscular cyst can present as an isolated finding. Materials and Methods Institutional review board approval was obtained, and HIPAA compliance was maintained throughout the study. Analysis of retrospective data for all patients who underwent MRI of the shoulder by the department of radiology at our institution between January 1998 and April 2006 revealed 5,101 shoulder MR examinations. Using the keywords interstitial tear, intramuscular cyst, intra substance tear, and ganglion cyst resulted in 187 examinations in 185 patients. Several keywords were searched because of the inter changeable use of these terms by radiologists at our institution to describe the same imaging finding. Regardless of the term, any rounded or fusiform fluid collection that was contained in the fascial sheath or substance of one of the muscles of the rotator cuff and that followed fluid signal intensity on all pulse sequences was used as the main inclusion factor (Fig. 1). For this article, this pathology will be referred to by the singular term intramuscular cyst, as commonly seen in the general literature. This selection criterion is similar to that used by previous studies describing the relationship between intramuscular cysts and rotator cuff tears [5]. Of the 187 examinations, 134 shoulders in 132 patients met our criteria for an intramuscular cyst, and 53 shoulders underwent arthroscopy. Each patient s medical records were reviewed, and the following information was recorded: site of intramuscular cysts, presence of rotator cuff disorder, location of potential rotator cuff disorder, and interpretation of arthroscopy data when available. Our data set comprised 134 shoulder examinations in 132 patients. Of the 132 patients fitting the inclusion criteria, 62 were female and 70 were male. The patients had a mean age of 53.2 years (range, 14 81 years). The right shoulder was in volved in 84 cases and the left shoulder in 50 cases. MRI Protocol All patients underwent MRI of the shoulder on a 1.5-T (Signa, GE Healthcare) scanner. A routine unenhanced shoulder protocol was performed in 100 shoulders and MR arthrography in 34 shoulders. The routine shoulder protocol evolved over time but generally included fat-suppressed oblique, co ronal, sagittal, and axial T2-weighted fast spin-echo (TR/ TE, 4,000/55) sequences. Also included were oblique coronal and axial fast spin-echo proton density weighted (3,000/23) se quences. A sagittal T1-weighted (500/13) sequence was also performed. The field of view was 12 16 cm and the slice thickness was 4 mm with a 0.4-mm interslice gap. The matrix size was 256 192 with two excita tions. All fast spin-echo T2-weighted images had frequency-selective fat sup pression. Thirty-four of the 134 studies were MR arthrography with similar protocol parameters; therefore, the field of view, number of excitations, and slice thickness were the same as for con ventional MRI. The MR arthrogra phy protocol included fat-suppressed T1- weighted images (1,600/13) in oblique coronal, oblique axial, and oblique sagittal planes. Fat-suppressed T2-weighted images were obtained in the same planes (TR/TE as above). An additional sagittal oblique T1 weighted, non fat-suppressed image was also obtained. A Fig. 1 25-year-old man with intramuscular cyst. A, Oblique sagittal fat-suppressed, fast spin-echo T2-weighted image shows rounded or fusiform focus contained in fascial sheath of supraspinatus muscle (arrow) and consistent with typical appearance of intramuscular cyst. B, Axial fat-suppressed, fast spin-echo T2-weighted image shows another view of isolated supraspinatus intramuscular cyst (arrow). Presence of intramuscular cyst was confirmed at arthroscopy. B 720 AJR:192, March 2009

Cysts in the Rotator Cuff Image Interpretation All MR images were independently evaluated retrospectively by three radiologists two of whom were trained in musculoskeletal radiology and one of whom was a senior radiology resident who had 30, 12, and 1 years of experience, respectively. The radiologists assessed the images for the presence of intramuscular cysts and rotator cuff tears. MRI criteria for an intramuscular cyst were a rounded or fusiform fluid collection that was contained in the fascial sheath or substance of one of the muscles of the rotator cuff and that followed fluid signal intensity on all pulse sequences. Rotator cuff tears were defined as areas of tendon discontinuity that showed increased signal intensity on proton density weighted images and remained of high signal intensity on T2-weighted sequences. Full-thickness tears were defined as tears that extended from the articular surface to the bursal surface of a given tendon. Partial-thickness tears were defined as tears that involved either the articular or bursal surface but did not extend through the full thickness of a tendon. Results Of the 134 shoulders with intramuscular cysts, 102 (76.1%) had radiologic evidence of both intramuscular cysts and rotator cuff tear (full- or partial-thickness). Forty-seven of 102 (46.1%) shoulders consisted of intramuscular cysts associated with a partial-thickness A Fig. 2 39-year-old man with partial-thickness rotator cuff tear and intramuscular cyst. A, Oblique coronal fat-suppressed, fast spin-echo T2-weighted image shows partial-thickness rotator cuff tear (rim rent) (dashed arrow) with corresponding supraspinatus intramuscular cyst (solid arrow). B, Oblique sagittal fat-suppressed, fast spin-echo T2-weighted image shows partial-thickness rotator cuff tear with corresponding supraspinatus intramuscular cyst (arrow). Presence of partial-thickness rotator cuff tear and intramuscular cyst were confirmed at arthroscopy. rotator cuff tear (Fig. 2), and 55 of 102 (53.9%) had a full-thickness tear (Fig. 3). Furthermore, in 48 of the 102 (47.1%) shoulders with both intramuscular cyst and a rotator cuff disorder, MRI was followed by arthroscopy to confirm the MRI findings. Thirty of the 48 shoulders that underwent arthroscopy had a full-thickness rotator cuff tear, and 18 of 48 had a partial-thickness tear Fig. 3 48-year-old woman with full-thickness rotator cuff tear and intramuscular cyst. Oblique sagittal T1-weighted image with fat suppression and injection of intraarticular dilute gadolinium reveals gadolinium solution in subacromial subdeltoid bursa, consistent with fullthickness rotator cuff tear. Intramuscular cyst is also noted in infraspinatus tendon in oblique sagittal plane (arrow). Presence of fullthickness rotator cuff tear and intramuscular cyst was confirmed at arthroscopy. by MRI criteria. In 46 of 48 (95.8%) shoulders that underwent arthroscopy, the surgical findings confirmed the preoperative MRI findings; the other two cases were shown to have an intact rotator cuff at arthroscopy. The remaining shoulders (54/102) diagnosed with both an intramuscular cyst and a rotator cuff tear (25 full-thickness and 29 partial-thickness) were treated nonsurgically. Thirty-two B AJR:192, March 2009 721

Manvar et al. shoulders (32/134) were diagnosed with only an intramuscular cyst and were not associated with a rotator cuff abnormality (Figs. 1 and 4). Five of the 32 shoulders underwent arthroscopy, and all five were confirmed to have intact rotator cuffs. Of the 134 shoulders with intramuscular cysts, 42 (31.3%) had intramuscular cysts confined to the supraspinatus tendon, 70 (52.2%) were isolated to the infraspinatus tendon, and eight (6.0%) involved the subscapularis tendon. Ten (7.5%) of the shoulders showed intramuscular cysts in both the supraspinatus and infraspinatus tendon; three (2.2%) shoulders consisted of intramuscular cysts in both the subscapularis and infraspinatus; and one (0.7%) shoulder involved separate fluid collections in the supraspinatus, infraspinatus, and subscapularis tendons. Furthermore, 34 of 134 cases that were found to have intramuscular cysts on conventional MRI underwent shoulder imaging with intraarticular gadolinium; in all 34 (100%) cases, the gadolinium filled the intramuscular cyst. Of the 102 shoulders associated with both intramuscular cyst and rotator cuff tear, there were 40 full-thickness and 35 partial-thickness rotator cuff tears in the supraspinatus tendon (73.5%). Of those with rotator cuff tears isolated to the supraspinatus tendon, 21 A Fig. 4 36-year-old man with intramuscular cyst but no rotator cuff tear. A, Oblique coronal fast spin-echo T2-weighted image with fat suppression reveals isolated intramuscular cyst in infraspinatus (arrow). B, Fast spin-echo T2-weighted image with fat suppression reveals isolated intramuscular cyst of infraspinatus (arrow) in oblique sagittal plane. Presence of intramuscular cyst was confirmed at arthroscopy. (28%) intramuscular cysts were associated with the supraspinatus, 42 (56.0%) with the infraspinatus, five (6.7%) with the subscapularis, five (6.7%) with both the infraspinatus and supraspinatus, and two with the infraspinatus and subscapularis. Tables 1 and 2 display the various combinations of torn rotator cuff muscles and coexisting intramuscular cysts and the spectrum of rotator cuff tears involved in this study. Discussion The accuracy of conventional MRI in diagnosing full-thickness rotator cuff tears ranges from 90% to 95% [1 3, 6]. The sensitivity and specificity of MR arthrography for the diagnosis of partial-thickness rotator cuff tears are 84 95% and 96 100%, respectively [7, 8]. However, the accuracy of conventional MRI in diagnosing partial-thickness rotator cuff tears ranges from 15% to 90% [1 3]. Thus, identifying secondary findings that may illuminate the need to carefully look for rotator cuff tears, especially partialthickness tears, is important. The association between intramuscular cysts and rotator cuff tears was first published as a case report in the orthopedic literature [9]. This association was further elucidated by Sanders et al. [4] and Kassarjian et al. [5], who showed correlations of 100% and 97%, respectively, between intramuscular cysts and full- and partial-thickness rotator cuff tears. Our study shows 102 of 134 (76.1%) intramuscular cysts to be associated with rotator cuff disorders. Of the 102 cases with both intramuscular cysts and rotator cuff tears, 55 (53.9%) had a full-thickness rotator-cuff tear and 47 (46.1%) had a partial-thickness tear (Figs. 2 and 3). This indicates that when intramuscular cysts present with rotator cuff tears, they can be present in almost equal proportions with either full-thickness or partial-thickness tears. These results are similar but not identical to those of the previous studies, which also indicated equal distribution of either full- or partial-thickness rotator cuff tears in patients with intramuscular cysts but a slightly increased likelihood of partial-thickness tears [4, 5]. In 43 of 102 (42.2%) cases with a confirmed location of both intramuscular cysts and rotator cuff tears, the intramuscular cyst was located in at least one of the tendons involved in that particular rotator cuff tear. For example, if a case involved a partial-thickness rotator cuff tear of both the infraspinatus and the supraspinatus, and the intramuscular cyst was found in the infraspinatus, then this individual has an intramuscular B 722 AJR:192, March 2009

Cysts in the Rotator Cuff TABLE 1: Relationship Between Rotator Cuff Tears and Location of Intramuscular Cysts Cyst Location Tear Location cyst located in at least one of the tendons involved in that particular tear. This differs from the findings by Kassarjian et al. [5], who found that in 24 of 31 (77.4%) cases, the intramuscular cyst was located in the tendon involved in the rotator cuff tear. In our study, this dichotomy was clearly evidenced by supraspinatus rotator cuff tendon tears. Although 75 cases involved rotator cuff tears of only the supraspinatus tendon (both partialand full-thickness tears), only 26 of 75 (34.7%) cases had a corresponding intramuscular cyst involving the supraspinatus tendon, whereas 49 of 75 (65.3%) had a corresponding intramuscular cyst involving the infraspinatus tendon. The accuracy of identifying intramuscular cysts on MRI is evidenced by the fact that 34 of 134 cases that were found to have intramuscular cysts on conventional MRI underwent shoulder imaging with intraarticular gadolinium; in all 34 (100%) cases, gadolinium filled the intramuscular cyst. A possible explanation for the association of these intramuscular cysts with rotator cuff tears is that the cysts are secondary to disruptions along the tendon attachments of the rotator cuff. In other words, a defect of the surface of the rotator cuff tendon may allow fluid from either the bursae or glenohumeral joint to enter the substance of the rotator cuff tendon and then track along the tendon fibers along the sheath or in the substance of the muscle [5, 10]. The collection of synovial fluid in these locations then produces the intramuscular cysts seen on MRI. These explanations are certainly plausible for coincident rotator cuff tendon tears and intramuscular cysts. Supraspinatus Infraspinatus Subscapularis Supraspinatus, Infraspinatus The presence of an intramuscular cyst involving a tendon not associated with a rotator cuff tear (either full- or partial-thickness) is a more difficult scenario to explain. For example, there was a high association in our series of supraspinatus rotator cuff tears with intramuscular cysts of the infraspinatus. Possibly small rotator cuff tears have occurred in the substance of the tendons that are not detected, which may in fact suggest more significant cuff disease. However, it is not yet clear whether an intramuscular cyst is a predictor of significant rotator cuff disorders. Longterm studies that follow intramuscular cysts would be necessary to determine whether they are accurate predictors of the subsequent development of a rotator cuff tear. The extremely high rate of association, 100% and 97%, found between intramuscular cysts and rotator cuff tears in the previous studies, Sanders et al. [4] and Kassarjian et al. [5], was not mirrored in our study. Instead, a significant portion of our study sample, 32 of 134 (23.9%) cases, was found to Infraspinatus, Subscapularis Supraspinatus, Infraspinatus, Subscapularis Unknown Supraspinatus 21 42 5 5 2 75 Infraspinatus 1 4 5 Subscapularis 2 1 3 Supraspinatus, infraspinatus 1 6 1 1 1 10 Supraspinatus, subscapularis 1 4 5 Infraspinatus, subscapularis 1 1 Infraspinatus, supraspinatus, subscapularis Infraspinatus, supraspinatus, teres minor 2 2 1 1 Total 27 59 6 6 2 1 1 102 TABLE 2: Distribution of Rotator Cuff Tears Total have intramuscular cysts alone without any rotator cuff tear on conventional MRI. In terms of follow-up, 48 of 102 (47.1%) cases with rotator cuff tear and intramuscular cysts underwent surgical intervention. Of these 48 cases, 30 (62.5%) were full-thickness rotator cuff tears and 18 (37.5%) were partialthickness tears. The remaining 54 (52.9%) cases were treated conservatively with either corticosteroid injections, pain medications, or rehabilitation. Of those treated conservatively, 25 of 54 (46.3%) were full-thickness rotator cuff tears and 29 (53.7%) were partial-thickness tears by MR criteria. Finally, five of the 32 patients with isolated intramuscular cysts without a related rotator cuff tear underwent arthroscopy. Of those patients, all five had an intact rotator cuff seen at arthroscopy. Limitations of our study include that not all patients diagnosed with rotator cuff tears on MRI had surgical follow-up for correlation of the findings. There are a variety of reasons for this, including patient s pain improved after Tear Location Partial-Thickness Full-Thickness Total Supraspinatus 35 40 75 Infraspinatus 5 0 5 Subscapularis 3 0 3 Supraspinatus, infraspinatus 3 7 10 Supraspinatus, subscapularis 0 5 5 Infraspinatus, subscapularis 1 0 1 Infraspinatus, supraspinatus, subscapularis 0 2 2 Infraspinatus, supraspinatus, teres minor 0 1 1 Total 47 55 102 AJR:192, March 2009 723

Manvar et al. rehabilitation, patient received follow-up and care at other institutions, and associated comorbidities that made patients poor surgical candidates. Also, not all patients with isolated intramuscular cysts had surgical follow-up to confirm the lack of a rotator cuff tear. The presence of intramuscular cysts was not mentioned in any of the arthroscopic interventions because of the inability to identify these intramuscular cysts with arthroscopy. These limitations are minimized by the fact that a significant proportion (47.1%) of patients did receive surgical follow-up for correlation of the findings, and a small percentage of isolated intramuscular cysts (18.8%) received surgical follow-up. Our study indicates that MRI is an accurate technology for identifying the presence of intramuscular cysts in the shoulder. Although our study echoes the sentiments of previous studies that suggest a relationship between intramuscular cysts and rotator cuff tears, it illustrates that the incidence of isolated intramuscular cysts is higher than previously expected. Moreover, the presence of intramuscular cysts remains an important predictor for possible rotator cuff tears, but it does not necessarily indicate whether the FOR YOUR INFORMATION tear is full-thickness or partial-thickness. Future directions of study in this area would involve tracking the progression of these isolated intramuscular cysts and to discover whether they are a harbinger of future rotator cuff tears. The radiologist should be made aware of the association of intramuscular cysts with rotator cuff tears in particular, partial-thickness rotator cuff tears to properly evaluate and diagnose these tears in patients. However, the absence of rotator cuff tears should not dissuade the radiologist from making a diagnosis of isolated intramuscular cysts. The significance of this finding in isolation remains unknown. References 1. Rafii M, Firooznia H, Sherman O, et al. Rotator cuff lesions: signal patterns at MR imaging. Radiology 1990; 177:817 823 2. Reinus WR, Shady KL, Mirowitz SA. MR diagnosis of rotator cuff tears of the shoulder: value of using T2-weighted fat-saturated images. AJR 1995; 164:1451 1455 3. Kaplan P, Helms C, Dussault R, Anderson M, Major N. Musculoskeletal MRI. Philadelphia, PA: Saunders, 2001 4. Sanders TG, Tirman PF, Feller JF, Genant HK. Association of intramuscular cysts of the rotator cuff with tears of the rotator cuff: MRI findings and clinical significance. AJR 2000; 16:230 235 5. Kassarjian A, Torriani M, Ouellette H, Palmer WE. Intramuscular rotator cuff cysts: association with tendon tears on MRI and arthroscopy. AJR 2005; 185:160 165 6. Balich SM, Sheley RC, Brown TR, Sauser DD, Quinn SF. MR imaging of the rotator cuff tendon: interobserver agreement and analysis of interpretive errors. Radiology 1997; 204:191 194 7. Ferrari FS, Governi S, Burresi F, Vigni F, Stefani P. Supraspinatus tendon tears: comparison of US and MR arthrography with surgical correlation. Eur Radiol 2002; 12:1211 1217 8. Meister K, Thesing J, Montgomery WJ, Indelicato PA, Walczak S, Fontenot W. MR arthrography of partial thickness tears of the undersurface of the rotator cuff: an arthroscopic correlation. Skeletal Radiol 2004; 33:136 141 9. Craig EV. The acromioclavicular joint cyst: an unusual presentation of a rotator cuff tear. Clin Orthop Relat Res 1986; 202:189 192 10. Clark JM, Harryman DT II. Tendons, ligaments, and capsule of the rotator cuff: gross and microscopic anatomy. J Bone Joint Surg 1992; 74:713 725 The comprehensive book based on the ARRS 2008 annual meeting categorical course on State-of-the-Art Emergency and Trauma Radiology is now available! For more information or to purchase a copy, see www.arrs.org. 724 AJR:192, March 2009