Tram-track appearance of the posterior cruciate ligament (PCL): correlations with mucoid degeneration, ligamentous stability, and differentiation from PCL tears.

OBJECTIVE: The purpose of our study was to describe the MRI findings in the posterior cruciate ligament (PCL) analogous to mucoid degeneration in the anterior cruciate ligament (ACL); to correlate MRI findings in the PCL with ligamentous stability; to differentiate the PCL tram-track appearance from the appearance of PCL tears; and to emphasize the coexistence of PCL and ACL mucoid degeneration, cruciate ganglia, and meniscal cysts. CONCLUSION: The tram-track PCL appearance commonly coexists with ACL mucoid degeneration; ganglia; and, less frequently, meniscal cysts. Both PCL tears and MRI findings suggestive of PCL mucoid degeneration show ligament thickening and increased PCL signal intensity. Tram-track PCLs are usually asymptomatic and typically have no ligamentous instability.

Elbow MR imaging findings in patients with synovial fringe syndrome.

OBJECTIVE: To describe imaging findings in patients with synovial fringe (SF) syndrome of the elbow and to compare with a control population. MATERIALS AND METHODS: Nine patients (5 men, 4 women) whose mean age was 35.7 years were diagnosed with SF syndrome and had undergone preoperative elbow MRI. The radiohumeral (RH) plica was assessed for thickness, cross-sectional area, coverage of one third or more of the radial head, blunting of the free edge, and T2 signal intensity abnormality. Other abnormalities of the RH joint were also assessed, including adjacent articular cartilage defects, subcortical bone marrow signal abnormality in the capitellum, and synovitis. Results were compared with 15 control patients who were asymptomatic laterally and posteriorly. RESULTS: Mean thickness and cross-sectional area of the RH plica were 1.8 mm and 19.4 mm(2) respectively in controls, compared with 2.5 mm and 21.9 mm(2) respectively in symptomatic patients. No statistically significant differences in the distribution of the mean thickness or cross-sectional area of the RH plica were found between the two groups. However, 67% of SF syndrome patients had a RH plica thickness greater than 2.6 mm compared with only 13% of controls (p = 0.021). Other abnormalities of the RH plica occurred more frequently in patients with SF syndrome compared with controls, but were not statistically significant. CONCLUSION: In patients presenting with posterolateral pain or mechanical symptoms in the elbow, RH plica thickness greater than 2.6 mm on elbow MRI examinations may help identify patients with SF syndrome.

Achados de ressonância magnética em cistos epidurais de origem discal em pacientes não operados e após microdiscectomia / Magnetic resonance imaging findings of disc-related epidural cysts in nonsurgical and postoperative microdiscectomy patients

OBJECTIVE: To demonstrate five discal cysts with detailed magnetic resonance imaging findings in nonsurgical and following postoperative microdiscectomy. MATERIALS AND METHODS: Five discal cysts in four patients who underwent magnetic resonance imaging were found through a search in our database and referral from a single orthopedic spine surgeon. Computed tomography in two cases and computed tomography discography in one case were also performed. RESULTS: Five discal cysts were present in four patients. Three patients had no history of previous lumbar surgery and the other patient presented with two discal cysts and recurrent symptoms after partial laminectomy and microdiscectomy. All were oval shaped and seated in the anterior epidural space. Four were ventrolateral, and the other one was centrally positioned in the anterior spinal canal. One showed continuity with the central disc following discography. Three were surgically removed. CONCLUSION: Magnetic resonance imaging can easily depict an epidural cyst and the diagnosis of a discal cyst should be raised when an homogeneous ventrolateral epidural cyst contiguous to a mild degenerated disc is identified.

OBJETIVO: Demonstrar os achados de imagem em cinco casos de cisto discal em pacientes sem cirurgia prévia e após microdiscectomia. MATERIAIS E MÉTODOS: Cinco cistos discais em quatro pacientes submetidos a exames de ressonância magnética foram identificados após procura em nossos sistemas de dados e por referência de um cirurgião ortopédico especialista em coluna. Exames de tomografia computadorizada também estavam disponíveis em dois casos e discografia por tomografia computadorizada em um caso. RESULTADOS: Três pacientes não tinham história prévia de cirurgia lombar e o outro paciente, que tinha dois cistos discais, apresentava recorrência dos sintomas após laminectomia parcial e microdiscectomia. Todos os cistos mostravam aspecto ovalado e estavam localizados no espaço epidural anterior, sendo quatro ventrolaterais, e o outro estava posicionado na região central do espaço epidural anterior. A discografia por tomografia computadorizada, disponível em um caso, demonstrou continuidade do cisto com o disco. Três foram submetidos a ressecção cirúrgica. CONCLUSÃO: A ressonância magnética pode facilmente identificar um cisto epidural e o diagnóstico de cisto discal deve ser considerado quando uma imagem cística homogênea, localizada no espaço epidural anterior, ventrolateral, e em contato com um disco parcialmente degenerado for identificada.

Pseudotear of the peroneus longus tendon on MRI, secondary to a fibrocartilaginous node.

OBJECTIVE: The purpose of this study was to identify the presence of a fibrocartilaginous node within the distal peroneus longus tendon (PLT) just proximal to the cubital tunnel and correlate this with MRI signal characteristics of the distal PLT, which could result in a pseudotear appearance on MRI. We correlated imaging characteristics with pathologic specimens. MATERIALS AND METHODS: Institutional review board approval was obtained. Retrospectively, 91 ankle MRIs utilizing a standard ankle protocol were reviewed by two musculoskeletal radiologists. Four cadaver ankles were imaged using a standard ankle MRI protocol and reviewed by the same radiologists. All the MRIs were examined for signal changes in the PLT. The cadaver ankles then underwent PLT dissection by an orthopaedic surgeon, and a pathologic review was undertaken by a pathologist with orthopaedic specialization, who looked for an os peroneum or proposed fibrocartilaginous node relating to the signal change found on the MRIs. RESULTS: In the 91 ankle MRI studies, the PLT demonstrated normal low and increased signals. On the fat-saturated T2-weighted sequence, 76 (83.5%) ankles demonstrated low signal and 15 (16.5%) demonstrated increased signal. Of the cadaver ankle MRIs, all four demonstrated increased signal within the PLT; three contained a fibrocartilaginous node and one contained an os peroneum in that same region. CONCLUSIONS: The MRI signal of the PLT can change with the presence of a fibrocartilaginous node, which may be due to the molecular and chemical content of the fibrocartilage. This node increases the MRI signal in the distal PLT and gives the appearance of a pseudotear.

Hemi-bucket-handle tears of the meniscus: appearance on MRI and potential surgical implications.

OBJECTIVES: To describe a type of meniscus flap tear resembling a bucket-handle tear, named a "hemi-bucket-handle" tear; to compare its imaging features with those of a typical bucket-handle tear; and to discuss the potential therapeutic implications of distinguishing these two types of tears. MATERIALS AND METHODS: Five knee MR examinations were encountered with a type of meniscus tear consisting of a flap of tissue from the undersurface of the meniscus displaced toward the intercondylar notch. A retrospective analysis of 100 MR examinations prospectively interpreted as having bucket-handle type tears yielded 10 additional cases with this type of tear. Cases of hemi-bucket-handle tears were reviewed for tear location and orientation, appearance of the superior articular surface of the meniscus, presence and location of displaced meniscal tissue, and presence of several classic signs of bucket-handle tears. RESULTS: A total of 15/15 tears involved the medial meniscus, had tissue displaced toward the notch, and were mainly horizontal in orientation. The superior surface was intact in 11/15 (73.3%). In 1/15 (6.7%) there was an absent-bow-tie sign; 6/15 (40%) had a double-PCL sign; 14/15 (93.3%) had a double-anterior horn sign. CONCLUSION: We describe a type of undersurface flap tear, named a hemi-bucket-handle tear, which resembles a bucket-handle tear. Surgeons at our institution feel this tear would likely not heal if repaired given its predominantly horizontal orientation, and additionally speculate the tear could be overlooked at arthroscopy. Thus, we feel it is important to distinguish this type of tear from the typical bucket-handle tear.

Evaluation of the glenoid labrum with 3-T MRI: is intraarticular contrast necessary?

OBJECTIVE: The purpose of this study was to evaluate the diagnostic accuracy of 3-T MRI versus 3-T MR arthrography for assessing labral abnormalities in the shoulder using arthroscopy as the gold standard. SUBJECTS AND METHODS: Forty-two patients (28 men, 14 women; mean age, 33 years) underwent MR arthrography and conventional MRI of the same shoulder. Two patients underwent bilateral shoulder examinations, for a total of 44 shoulder examinations. Twenty-two shoulders underwent arthroscopy. The results of arthroscopy were used as the reference standard. Three musculoskeletal radiologists prospectively and independently interpreted MRI and MR arthrography examinations. Differences in performance of conventional MRI and MR arthrography were analyzed for statistical significance by the two-tailed McNemar test. RESULTS: Of the 22 arthroscopies performed, 26 labral tears were found in 18 shoulders and four shoulders were normal with respect to the labrum. There were 12 superior, nine posterior, and five anterior labral tears identified at arthroscopy. By consensus review, conventional MRI identified nine of 12 superior (sensitivity, 75%; specificity, 100%), seven of nine posterior (sensitivity, 78%; specificity, 92%), and three of five anterior (sensitivity, 60%; specificity, 94%) labral tears. MR arthrography identified nine of 12 superior (sensitivity, 75%; specificity, 100%), eight of nine posterior (sensitivity, 89%; specificity, 100%), and five of five anterior (sensitivity, 100%; specificity, 100%) labral tears. CONCLUSION: Although the power of our preliminary study is small, the results suggest that intraarticular contrast material is helpful in diagnosing labral tears in the shoulder, particularly tears of the anterior labrum. Our preliminary results suggest that MR arthrography adds value for diagnosing labral tears in the shoulder compared with conventional MRI even at 3 T.

Wrisberg variant of the discoid lateral meniscus with flipped meniscal fragments simulating bucket-handle tear: MRI and arthroscopic correlation.

An MRI diagnosis of the Wrisberg variant discoid lateral meniscus should be considered in patients presenting with an anteriorly flipped posterior horn fragment without a definable peripheral rim. We present four cases discovered on arthroscopy that were thought to resemble bucket-handle tears on preoperative MRI. Posterior hypermobility poses a surgical challenge as excessive debridement without careful attention to underlying meniscal morphology may lead to further instability. Although this diagnosis can be difficult to make on MRI, alerting the orthopedic surgeon preoperatively may influence repair technique and meniscus conservation.

Magnetic resonance arthrography of the shoulder: accuracy of gadolinium versus saline for rotator cuff and labral pathology.

OBJECTIVE: The purpose of this study was to evaluate the necessity of intra-articular gadolinium versus saline alone in magnetic resonance arthrography (MRA) of the shoulder. MATERIALS AND METHODS: Our database was reviewed for 100 consecutive shoulder MRA examinations performed between January 2007 and December 2007. Patient information was blinded and images were retrospectively reviewed by at least two radiologists with dedicated musculoskeletal training. T2-weighted (T2W) images were initially analyzed in isolation to simulate MRA with saline alone. After a delay, the full study was analyzed including T1-weighted (T1W) and T2W images. If there was a significant discordance between the two analyses with regard to rotator cuff or labral pathology, the study was again reviewed by all evaluators in consensus to determine if the T1W images offered additional diagnostic information and increased diagnostic confidence. RESULTS: Of the 100 MRA examinations, there were 15 discordant cases. Two cases were discordant with regard to rotator cuff pathology and 13 were discordant on the basis of labral pathology. When the discordant cases were reviewed in consensus, the T2W images appeared to display rotator cuff and labral pathology as definitively as the T1W images. Interobserver and intraobserver variability was favored to have played a role in causing the discordances. CONCLUSIONS: MRA of the shoulder performed with joint distention provided by saline alone appears to offer equivalent diagnostic information to MRA performed with gadolinium enhancement. This protocol modification improves efficiency by eliminating several image series and provides a small cost savings by eliminating gadolinium.

New observations on meniscal cysts.

OBJECTIVE: The purpose of this study was to determine the incidence of meniscal cysts, assess the frequency of various magnetic resonance (MR) imaging characteristics, and emphasize radiographic observations not commonly reported. MATERIALS AND METHODS: A total of 2,095 consecutive knee MR imaging reports from a 22 month period were retrospectively reviewed for the presence of meniscal cysts. Two musculoskeletal radiologists reviewed the cases where cysts were reported. A meniscal cyst was considered present if abnormally increased signal was identified within an enlarged meniscus (i.e., intrameniscal cyst) or if a loculated fluid-intensity lesion with a clear connection to the adjacent meniscus was identified (i.e., parameniscal cyst). Presence or absence of a meniscal tear, intrameniscal and parameniscal signal intensity, patient age, sex, location of meniscal cyst, presence of discoid meniscus, and size of the parameniscal cyst component were recorded. All knee imaging examinations were performed on a 1.5T MR unit. Imaging findings were correlated with arthroscopic reports when available. RESULTS: A total of 167 cases (8.0%) of meniscal cysts were diagnosed in 161 patients. Of the 167 cysts, 69 (41.3%) were located in the lateral meniscus and 98 (58.7%) in the medial meniscus. In 6 patients (3.7%), meniscal cysts were present in both menisci of the same knee. Twelve (7.2%) meniscal cysts were associated with discoid menisci. Ninety-seven (57.8%) meniscal cysts were associated with meniscal tears. Of the total number of meniscal cysts, 104 (62.3%) had a parameniscal cyst. An isolated intrameniscal cyst was present in 63 (37.7%) cases. One hundred (96%) of the parameniscal cyst components were isointense to fluid on T2-weighted FSE images. All cysts exhibited abnormal intrameniscal signal. Only 14 (8.4%) of the intrameniscal components were isointense to fluid on T2-weighted FSE images. The arthroscopic reports of 88 of the 161 (54.7%) patients were available for review and correlation. A tear extending to the articular surface of the meniscus was reported to be present in 74 of the 88 (84%) arthroscopic examinations. CONCLUSIONS: Knowledge of the spectrum of findings and the relative frequency of various MR imaging characteristics as well as common potential pitfalls is important to the accurate diagnosis and management of mensical cysts. In particular, controversy exists as to the incidence of articular surface tears in association with meniscal cysts, with some authors reporting greater than 98% correlation with tears. Only 58% of cysts were associated with an articular surface tear. Ninety six percent of the parameniscal signal was isointense to fluid, only 8% of the intramensical signal was isointense to fluid.

MRI findings associated with luxatio erecta humeri.

OBJECTIVE: Luxatio erecta humeri is a rare type of inferior glenohumeral dislocation with a unique radiographic appearance; however, the magnetic resonance imaging findings associated with this dislocation have not been described in the radiology literature. The purpose of this study is to identify magnetic resonance imaging findings associated with this uncommon type of glenohumeral dislocation. MATERIALS AND METHODS: The magnetic resonance imaging features of four patients with clinical and radiographic evidence of luxatio erecta humeri were reviewed retrospectively by two musculoskeletal-trained radiologists. The reported mechanism of injury in all four patients was falling. The MR imaging examinations were evaluated for the presence of rotator cuff and biceps tendon pathology, glenoid labrum pathology, joint capsule and glenohumeral ligament injury, fractures and bone marrow contusions, articular cartilage injury, and joint effusions. RESULTS: All four patients demonstrated pathology of the glenohumeral joint. Three of the four patients demonstrated rotator cuff tears, including large full thickness tears of the supraspinatus and infraspinatus tendons in two patients, and small full thickness tear of the supraspinatus tendon with partial thickness tear of the infraspinatus tendon in the third patient. In the two patients with large full thickness tears of the supraspinatus and infraspinatus tendons, one patient demonstrated tearing of the subscapularis tendon with dislocation of a partially torn long head of the biceps tendon, and the second patient demonstrated full thickness tearing of the intra-articular biceps tendon. All four patients demonstrated injuries to the glenoid labrum and both anterior and posterior bands of the inferior glenohumeral ligament. Contusions or fractures of the humeral head were seen in two of the patients. Three of the four patients demonstrated cartilage abnormalities including a focal cartilage defect in the anterior inferior glenoid in one patient, and cartilage surface irregularity of the glenoid in the other two patients. CONCLUSION: Common magnetic resonance imaging findings in patients with a prior luxatio erecta humeri dislocation include rotator cuff tears, injury to the glenoid labrum, and injury to both the anterior and posterior bands of the inferior glenohumeral ligament. These findings are compatible with the mechanism of dislocation in luxatio erecta, and noting these findings on magnetic resonance imaging may suggest that the patient has sustained a prior inferiorly directed glenohumeral dislocation such as luxatio erecta.

MRI appearance of posterior cruciate ligament tears.

OBJECTIVE: There is little in the radiology literature regarding the MRI appearance of a torn posterior cruciate ligament (PCL). The purpose of this study was to describe the MRI appearance of surgically proven PCL tears and to emphasize previously unreported signs. CONCLUSION: The PCL is usually injured as the result of stretching deformation; on MRI, the ligament maintains continuity as a single structure with apparent thickening. On sagittal T2-weighted images, an anteroposterior diameter of 7 mm or more is highly suggestive of a torn PCL. Increased intrasubstance signal intensity in the PCL on proton-density images with lower signal intensity on T2-weighted images is another common feature.

The posterolateral corner of the knee.

OBJECTIVE: The purpose of this article is to review the clinical importance and MRI appearances of injuries to the posterolateral corner of the knee. CONCLUSION: Injuries to the posterolateral corner structures of the knee can cause significant disability due to instability, cartilage degeneration, and cruciate graft failure. Becoming familiar with the anatomy of this region can improve one's ability to detect subtle abnormalities and can perhaps lead to improvements in diagnosing and understanding injuries to this area.

MRI appearance of surgically proven abnormal accessory anterior-inferior tibiofibular ligament (Bassett's ligament).

OBJECTIVE: A thickened accessory anterior-inferior tibiofibular ligament (Bassett's ligament) of the ankle can be a cause of ankle impingement. Its imaging appearance is not well described. The purpose of this study was to determine if the ligament could be identified on magnetic resonance imaging (MRI), to determine associated abnormalities, and to determine if MRI could be used to differentiate normal from abnormal. MATERIALS AND METHODS: Eighteen patients with a preoperative ankle MRI and an abnormal Bassett's ligament reported at surgery were found retrospectively. A separate cohort of 18 patients was selected as a control population. The presence of Bassett's ligament and its thickness were noted. The integrity and appearance of the lateral ankle ligaments, talar dome cartilage, and anterolateral gutter were also noted. RESULTS: In 34 of the 36 cases (94%), Bassett's ligament was identified on MRI. The ligament was seen in all three imaging planes and most frequently in the axial plane. The mean thickness of the ligament in the surgically abnormal cases was 2.37 mm, compared with 1.87 mm in the control with a p value=0.015 (t test). Nine of the 18 abnormal cases (50%) had talar dome cartilage lesions as a result of contact with the ligament at surgery, with only 3 cases of high-grade defects seen on MRI. Fourteen of the 18 abnormal cases (78%) had of synovitis or scarring in the lateral gutter at surgery, with only 5 cases with scarring seen on MRI. The anterior-inferior tibiofibular ligament was abnormal or torn in 8 of the 18 abnormal cases (44%) by MRI and confirmed in only 3 cases at surgery. DISCUSSION: Bassett's ligament can be routinely identified on MRI and was significantly thicker in patients who had it resected at surgery. An abnormal Bassett's ligament is often present in the setting of a normal anterior-inferior tibiofibular ligament. The cartilage abnormalities and synovitis associated with an abnormal Bassett's ligament are poorly detected by conventional MRI.

Disc space-targeted angled axial MR images of the lumbar spine: a potential source of diagnostic error.

OBJECTIVE: To compare the sensitivities of contiguous axial (CA) images and disc space-targeted angled axial (DSTAA) images of the lumbar spine for: (1) the detection of spondylolysis defects, and (2) the identification of disc material which has migrated away from the parent disc. MATERIALS AND METHODS: Prospective imaging of the lumbar spine was performed over a 22-month period in 103 patients. Imaging protocols included spin-echo T1- and fast spin-echo (FSE) T2-weighted images in the sagittal and axial planes. For each patient, axial images were obtained both contiguously throughout the lumbar spine and as angled images, targeted at the region of the disc space only. Two separate data sets were compiled: one that included contiguous axial images (CA data set) and another that included targeted angled images through the disc spaces only (DSTAA data set). Identical sagittal images were included with both sets. A single radiologist independently interpreted the two data sets for a given patient following an intervening time lapse. The radiologist was blinded to the initial interpretation. Results from the two independent interpretations were then compared. RESULTS: Spondylolysis defects were identified at 15 different levels in 14 patients (14%) using the contiguous axial imaging protocol compared with 8 (7%) identified using the disc space targeted angled axial imaging protocol (P = 0.12). Migrated disc material was identified in 12 patients (12%) using the CA protocol compared with 3 patients (3%) identified with the DSTAA protocol (P = 0.016). CONCLUSIONS: MR imaging of the lumbar spine using contiguous axial data obtained through both the level of the disc and vertebral body demonstrates migrated disc material and spondylolysis defects better than did disc space-targeted angled data.

Rim-rent tear of the rotator cuff: a common and easily overlooked partial tear.

OBJECTIVE: The purpose of this study was to determine the incidence of rim-rent rotator cuff tears in a population of patients referred for shoulder MRI and to determine the sensitivity of MRI for the detection of these tears. CONCLUSION: Rim-rent tears are a common type of partial-thickness rotator cuff tear, much more commonly present than has been previously reported. In particular, infraspinatus rim-rent tears are more common than previously believed. Rim-rent tears of the infraspinatus tendon and those involving the anterior-most fibers of the supraspinatus tendon are commonly overlooked on MRI, possibly because of failure to appreciate the high incidence of these types of tears and failure to inspect the anterior-most fibers of the rotator cuff.

MRI of the posterolateral corner injury: a concise review.

The posterolateral corner of the knee represents a complicated area of anatomy and function. Failure to recognize injury to the posterolateral structures in the acute setting can result in long-term disability. Magnetic resonance imaging (MRI) provides a noninvasive evaluation of such structures. A systematic and simplified approach to the MRI evaluation of posterolateral corner injury can aid in diagnosis and subsequent surgical consideration.

MRI appearance of Wrisberg variant of discoid lateral meniscus.

OBJECTIVE: A discoid lateral meniscus is a common normal variant, occurring in approximately 3-5% of the population. A subgroup of the discoid lateral meniscus known as the Wrisberg variant occurs when there is no posterior attachment of the lateral meniscus. Instead, Wrisberg's ligament becomes the only lateral meniscus posterior stabilizer, with a symptomatic hypermobile meniscus. Although it is commonly described in the orthopedics literature, to our knowledge the Wrisberg variant of the discoid lateral meniscus is not mentioned in the radiology literature. This article describes the MRI appearance of this important yet often unrecognized process. CONCLUSION: The Wrisberg variant of the discoid lateral meniscus is a rare condition with a highly suggestive clinical history. The musculoskeletal radiologist should consider this diagnosis whenever a discoid lateral meniscus is identified because making this elusive diagnosis may prove immensely useful for the orthopedic surgeon.

Parsonage-Turner syndrome: MR imaging findings and clinical information of 27 patients.

PURPOSE: To review retrospectively the magnetic resonance (MR) imaging findings and clinical information of patients with Parsonage-Turner syndrome (PTS). MATERIALS AND METHODS: The institutional review board did not require its formal approval or informed patient consent at the time of the study. However, the study was HIPAA compliant. The information in a computerized database of 2875 consecutive shoulder MR examinations was retrospectively reviewed. With use of key terms, the database software identified 81 examinations potentially associated with PTS. Both authors together reviewed the 81 imaging reports and the corresponding patients' medical records. In consensus, they made the diagnosis of PTS in 21 patients (two with bilateral involvement) on the basis of MR findings, electromyographic results, and clinical data. They also examined the data of an additional six patients (one with bilateral involvement) obtained from outside facilities. Ultimately, 30 shoulders of 27 patients (18 male, nine female; age range, 12-81 years; mean age, 41 years) were evaluated. The MR findings and clinical information (ie, regarding atrophy, pain, weakness, electromyographic results, neck and spine history, trauma, excessive overhead activity, recent surgery, vaccination, and illness) of all patients with PTS were reviewed. MR findings of diffuse high T2 signal intensity abnormality and fatty atrophy of muscles were evaluated to assess the pattern of nerve involvement. Structural causes (eg, ganglion cyst or other mass) of neurogenic high T2 signal intensity abnormality were excluded at MR imaging. RESULTS: Twenty-nine (97%) of 30 shoulders had suprascapular nerve involvement; in 15 (50%) shoulders, the involvement was limited to this nerve. Fifteen (50%) shoulders had axillary nerve involvement; in only one (3%) shoulder, the involvement was limited to this nerve. One shoulder (3%) had subscapular nerve involvement. Nine (30%) shoulders demonstrated focal muscular atrophy. Eleven (41%) of 27 patients also underwent electromyography; all of these patients demonstrated neuropathies that matched the patterns of neurogenic high T2 signal intensity abnormality seen at MR imaging. CONCLUSION: The suprascapular nerve was almost invariably involved (in 97% of shoulders) in patients with PTS. Axillary nerve involvement also was commonly observed (in 50% of shoulders). Subscapular nerve involvement was uncommon (in 3% of shoulders).