Beyond schwannomas and neurofibromas: a radiological and histopathological review of lesser-known benign lesions that arise in association with peripheral nerves.

Peripheral nerve sheath tumors comprise a significant percentage of both benign and malignant soft tissue tumors. The vast majority of these lesions are schwannomas and neurofibromas, which most radiologists are familiar with including the well-described multimodality imaging features. However, numerous additional often under-recognized benign entities associated with nerves exist. These rarer entities are becoming increasingly encountered with the proliferation of cross-sectional imaging, particularly magnetic resonance imaging (MRI). It is important for the radiologist to have a basic understanding of these entities as many have near-pathognomonic MR imaging features as well as specific clinical presentations that when interpreted in concert, often allows for a limited differential or single best diagnosis. The ability to provide a prospective, pre-intervention diagnosis based solely on imaging and clinical presentation is crucial as several of these entities are "do not touch" lesions, for which even a biopsy may have deleterious consequences. To our knowledge, the majority of these benign entities associated with nerves have only been described in scattered case reports or small case series. Therefore, the aim of this article is to provide a radiopathologic comprehensive review of these benign entities that arise in association with nerves with a focus on characteristic MRI features, unique histopathologic findings, and entity specific clinical exam findings/presentation.

Effect of Pulsed Low-Intensity Ultrasonography on Symptom Relief and Tibiofemoral Articular Cartilage Thickness Among Veterans Affairs Enrollees With Knee Osteoarthritis: A Randomized Clinical Trial.

Importance: Osteoarthritis (OA) is a major cause of disability in the US, with no approved treatments to slow progression, but animal models suggest that pulsed low-intensity ultrasonography (PLIUS) may promote cartilage growth. Objective: To evaluate the efficacy of PLIUS in providing symptom reduction and decreased loss of tibiofemoral cartilage thickness in patients with knee OA. Design, Setting, and Participants: A phase 2A, sham-controlled, parallel, double-blind randomized clinical trial was conducted at 2 Veterans Affairs hospitals in Salt Lake City, Utah, and San Diego, California, from May 22, 2015, to January 31, 2019. Data were analyzed from June 27, 2020, to October 20, 2020. Participants recruited through the US Department of Veterans Affairs (N = 132) with clinical and radiographic evidence of early knee OA were randomly assigned to receive PLIUS or a sham device, self-administered for 20 minutes daily over the medial compartment of the knee. All enrollees participated in a 4-week prerandomization sham run-in period, followed by a 48-week treatment period. Randomization was stratified by study site and Kellgren-Lawrence grades 1 (n = 15), 2 (n = 51), and 3 (n = 66). Intervention: Participants either received 48 weeks of PLIUS or sham ultrasonography. Main Outcomes and Measures: The trial incorporated 2 coprimary outcomes: symptomatic improvement assessed by Outcome Measures in Rheumatology Clinical Trials-Osteoarthritis Research Society International Responder Criteria (ie, met if either >50% improvement in pain and function with at least a 20% absolute improvement of at least 2 of the following 3 factors: improvement by at least 20% [pain, function, and patient global assessment] with at least a 10-mm absolute improvement), and cartilage preservation assessed as change in central medial femoral condyle cartilage thickness by magnetic resonance imaging. Intention-to-treat analysis was used. Results: The mean (SD) participant age was 63.6 (10.7) years and 119 were men (90.2%). The mean (SD) duration of OA symptoms was 13.4 (12.3) years. In the PLIUS group, 70.4% (95% CI, 58.2%-82.6%) of the participants experienced symptomatic improvement, compared with 67.3% (95% CI, 54.9%-79.7%) of participants in the sham group (P = .84); there was no statistically significant difference in response rates between the treatment groups, and the between-group rate difference of 3.1% (95% CI, -14.3% to 20.5%) did not meet the predefined 10% threshold for clinically significant symptomatic improvement from application of PLIUS. At 48 weeks of treatment, central medial femoral condyle cartilage thickness decreased by a mean (SD) of 73.8 (168.1) µm in the PLIUS group and by 42.2 (297.0) µm in the sham group. This 48-week mean change between the 2 groups did not reach statistical significance (P = .44), and the between-group 48-week difference of -31.7 µm (95% CI, -129.0 µm to 65.7 µm) did not meet the predefined threshold. There were 99 nonserious adverse events in the PLIUS group and 89 in the sham group during the trial. No serious adverse events were deemed related to the study device. Conclusions and Relevance: PLIUS, as implemented in this study, demonstrated neither symptomatic benefit nor a decrease in loss of tibiofemoral cartilage thickness in knee OA. Trial Registration: ClinicalTrials.gov Identifier: NCT02034409.

Septic Arthritis: An Evidence-Based Review of Diagnosis and Image-Guided Aspiration.

OBJECTIVE. The purpose of this evidence-based review is to equip radiologists to discuss and interpret findings obtained with various imaging modalities, guide patient selection for percutaneous aspiration, and safely perform arthrocentesis to assess for infection in both native and prosthetic joints. CONCLUSION. Septic arthritis is an emergency that can lead to rapidly progressive, irreversible joint damage. Despite the urgency associated with this diagnosis, there remains a lack of consensus regarding many aspects of the management of native and periprosthetic joint infections.

Untreated plasmacytoma of bone containing macroscopic intralesional fat and mimicking intraosseous lipoma: A case report and review of the literature.

Solitary plasmacytoma is a rare form of plasma cell neoplasm defined by local neoplastic accumulation of monoclonal plasma cells in the absence of systemic proliferative plasma cell disease. In this case report, a 65-year-old female with remote past medical history of papillary thyroid cancer presented with shoulder pain and radiographs showing an aggressive osteolytic lesion presumed to represent an osseous metastasis. The subsequent MRI and CT examinations demonstrated diffuse intralesional macroscopic fat without a nonlipogenic soft tissue component or focal, nodular mass-like enhancement. The presence of macroscopic fat in an untreated osseous lesion suggested a benign lesion with the favored diagnosis an intraosseous lipoma with non-displaced pathological fracture. Therefore, the decision was made to forego image-guided percutaneous biopsy and instead proceed directly to open surgical biopsy and partial distal claviculectomy. Pathology of the resected specimen showed focally dense infiltration of plasma cells within the marrow space and scant hematopoiesis compatible with a plasma cell neoplasm. To the best of our knowledge, this is first case report of solitary plasmacytoma of bone, or any untreated plasma cell neoplasm, containing macroscopic fat upon imaging. The decision to forego image-guided percutaneous biopsy had significant treatment implications as the primary therapy for patients with SPB is not surgical, but localized radiation therapy. Based on this case, solitary plasmacytoma of bone may be included as one of the rare fat containing malignant bone lesions and imaging guided percutaneous biopsy should be considered in symptomatic fat-containing bone lesions.

Avulsion Injuries of the Hand and Wrist.

Injuries of the hand and wrist are frequently encountered in radiology. Avulsions of the hand and wrist are a heterogeneous group of injuries, but they often have a characteristic imaging appearance that relates to the intricate bone and soft-tissue anatomy and the mechanism of injury. The imaging appearance and this intricate form and function dictate treatment of hand and wrist avulsions. This article reviews frequently and infrequently encountered avulsion injuries and describes abnormalities that may mimic the imaging appearance of avulsions. Specifically discussed entities include the Bennett and reverse Bennett fracture, ulnar collateral ligament avulsion, radial and ulnar styloid process avulsion, triquetral avulsion, mallet and jersey finger, central slip avulsion, and acute and chronic volar plate avulsion injuries. Uncommon avulsion injuries are also described and include avulsions of the scapholunate ligament, extensor carpi radialis longus and brevis tendons, trapeziometacarpal ligament, radial collateral ligament, and flexor digitorum profundus tendon. Emphasis is placed on the relevant anatomy and typical imaging findings for each diagnosis, with pertinent clinical history, pathophysiologic evaluation, and treatment discussed briefly. Understanding the anatomy and expected imaging findings can aid the radiologist in recognizing and characterizing these injuries.©RSNA, 2020.

Pearls and Pitfalls for Soft-Tissue and Bone Biopsies: A Cross-Institutional Review.

Management of soft-tissue and bone neoplasms depends on a definitive histologic diagnosis. Percutaneous image-guided biopsy of bone and soft-tissue tumors is a cost-effective and accurate method to obtain a histopathologic diagnosis. Biopsy requests must be approached thoughtfully to avoid numerous potential pitfalls. Hasty biopsy planning places the patient at increased risk for misdiagnosis, delayed therapy, repeated invasive procedures, and substantial morbidity. Biopsy planning begins with a thorough review of the relevant clinical history and pertinent imaging. The biopsy route must be planned in concert with the referring orthopedic oncologist to preserve limb-sparing options. Carefully selecting the most appropriate imaging modality to guide the biopsy increases the chances of reaching a definitive diagnosis. It is also critical to identify and target with expertise the part of the lesion that is most likely to yield an accurate diagnosis. Percutaneous biopsy is a safe procedure, and familiarity with preprocedural laboratory testing parameters, anticoagulation guidelines, and commonly used sedation medications minimizes the risk of complications while ensuring patient comfort. Nondiagnostic biopsy results are not infrequent and may still have value in guiding patient treatment. Awareness of the imaging manifestations of tumor recurrence is also important. The aim of this article is to provide a comprehensive review of pertinent preprocedural, periprocedural, and postprocedural considerations for bone and soft-tissue musculoskeletal biopsies.The online slide presentation from the RSNA Annual Meeting is available for this article.©RSNA, 2020.

Radiographic Evidence of Soft-Tissue Gas 14 Days After Total Knee Arthroplasty Is Predictive of Early Prosthetic Joint Infection.

OBJECTIVE. The diagnosis of early prosthetic joint infection (PJI)-defined as within 6 weeks after a total knee arthroplasty (TKA)-can be difficult because of expected postsurgical changes and elevated inflammatory markers. The role of radiographic evaluation in this situation carries unclear clinical significance. This study had three primary aims: first, to determine when soft-tissue gas is no longer an expected postoperative radiographic finding; second, to determine whether soft-tissue gas is predictive of early PJI; and, third, to determine whether the presence of soft-tissue gas correlates with specific patient characteristics and microbiology culture results. MATERIALS AND METHODS. This retrospective study was of patients who underwent TKA from 2008 to 2018 with available imaging between 5 days and 6 weeks after TKA and no interval intervention before imaging. All confirmed early PJIs were included (n = 24 cases; 15 patients). For comparison, patients who underwent TKA but did not have a PJI (n = 180 cases; 150 patients) were selected randomly. Radiographs were reviewed by two readers. A two-tailed p < 0.05 was considered significant. RESULTS. Soft-tissue gas was identified on postoperative radiography of 13 of 24 (54.2%) cases (mean ± standard error of the mean [SEM], 28.3 ± 2.3 days after TKA) with early PJI and four of 180 (2.2%) cases (mean ± SEM, 15.3 ± 7.3 days after TKA) without PJI (p < 0.0001; odds ratio, 52.0 [95% CI, 14.7-156.9]). The presence of soft-tissue gas on radiography 14 days after TKA had a sensitivity of 0.54 (95% CI, 0.35-0.72) and specificity of 0.99 (95% CI, 0.97-1.00) for early PJI. Staphylococcus species were the dominant organisms; cases with soft-tissue gas showed a wider variety of microbiology species (p < 0.01). CONCLUSION. Postoperative soft-tissue gas present on radiography performed 14 days or more after TKA is predictive of early PJI and is associated with a wider spectrum of microorganisms.

Pearls and pitfalls of fluoroscopic-guided foot and ankle injections: what the radiologist needs to know.

OBJECTIVE: This article provides a comprehensive, joint-by-joint review of fluoroscopic-guided foot and ankle injections and emphasizes pre-procedural planning, relevant anatomy, appropriate technique, troubleshooting the difficult procedure, and the importance of communicating unexpected findings with the referring clinician. The interrogation of pain generators including variant ossicles, fractures, and post-surgical/traumatic findings is also described. CONCLUSIONS: Even the most challenging foot and ankle injections may be successfully completed with a solid anatomical understanding and thoughtful approach.

Spinal Marrow Imaging: Clues to Disease.

Benign and malignant as well as focal and diffuse disease processes can involve the spinal marrow. This is a review of the commonly encountered spinal marrow abnormalities and the distinguishing magnetic resonance features that may provide clues to disease.

Exercise-stimulated arterial transit time in calf muscles measured by dynamic contrast-enhanced magnetic resonance imaging.

The primary goal of this study was to evaluate arterial transit time (ATT) in exercise-stimulated calf muscles as a promising indicator of muscle function. Following plantar flexion, ATT was measured by dynamic contrast-enhanced (DCE) MRI in young and elderly healthy subjects and patients with peripheral artery disease (PAD). In the young healthy subjects, gastrocnemius ATT decreased significantly (P < 0.01) from 4.3 ± 1.5 to 2.4 ± 0.4 sec when exercise load increased from 4 lbs to 16 lbs. For the same load of 4 lbs, gastrocnemius ATT was lower in the elderly healthy subjects (3.2 ± 1.1 sec; P = 0.08) and in the PAD patients (2.4 ± 1.2 sec; P = 0.02) than in the young healthy subjects. While the sensitivity of the exercise-stimulated ATT is diagnostically useful, it poses a challenge for arterial spin labeling (ASL), a noncontrast MRI method for measuring muscle perfusion. As a secondary goal of this study, we assessed the impact of ATT on ASL-measured perfusion with ASL data of multiple post labeling delays (PLDs) acquired from a healthy subject. Perfusion varied substantially with PLD in the activated gastrocnemius, which can be attributed to the ATT variability as verified by a simulation. In conclusion, muscle ATT is sensitive to exercise intensity, and it potentially reflects the functional impact of aging and PAD on calf muscles. For precise measurement of exercise-stimulated muscle perfusion, it is recommended that ATT be considered when quantifying muscle ASL data.

Naviculocuneiform and Second and Third Tarsometatarsal Articulations: Underappreciated Normal Anatomy and How It May Affect Fluoroscopy-Guided Injections.

OBJECTIVE: Because the second and third tarsometatarsal (TMT) and naviculocuneiform joints normally communicate, the least arthritic or technically most straightforward joint was injected when a fluoroscopically guided therapeutic injection was ordered for one or both joints. We hypothesized that pain relief would be equivalent regardless of the joint injected and would result in less radiation and a lower steroid dose compared with patients who had both articulations injected. MATERIALS AND METHODS: Seventy-eight patients were divided into four joint groups: naviculocuneiform requested and injected (n = 15), nonrequested naviculocuneiform or second and third TMT injected (n = 25), both injected (n = 23), and TMT requested and injected (n = 15). Variables recorded included patient age and sex, fluoroscopy time, steroid dose, pre- and postprocedural pain, osteoarthrosis (OA) grade, and confidence of intraarticular injection. Statistical analysis compared mean pain level change before and after injection, mean fluoroscopy time, and mean steroid dose between groups. The mean OA grade of the nonrequested joint was compared with that of the requested joint in patients whose injected and requested joints did not match (group 2). RESULTS: Pre- and postinjection pain reduction (p = 0.630) and postinjection pain (p = 0.935) were not significantly different. Mean steroid dose (p < 0.001) and fluoroscopy time (p = 0.0001) were significantly increased for the both joint injection group. Within the nonrequested naviculocuneiform or second and third TMT injection group, there was a significant difference in OA grade between injected (least arthritic) and requested joints (p = 0.001). CONCLUSION: When faced with challenging naviculocuneiform or second and third TMT joint injections, choosing the technically most straightforward joint may result in less radiation and steroid dose without compromising quality of care or pain reduction.

Exercise-induced calf muscle hyperemia: quantitative mapping with low-dose dynamic contrast enhanced magnetic resonance imaging.

Peripheral artery disease (PAD) in the lower extremities often leads to intermittent claudication. In the present study, we proposed a low-dose DCE MRI protocol for quantifying calf muscle perfusion stimulated with plantar flexion and multiple new metrics for interpreting perfusion maps, including the ratio of gastrocnemius over soleus perfusion (G/S; for assessing the vascular redistribution between the two muscles) and muscle perfusion normalized by whole body perfusion (for quantifying the muscle's active hyperemia). Twenty-eight human subjects participated in this Institutional Review Board-approved study, with 10 healthy subjects ( group A) for assessing interday reproducibility and 8 healthy subjects ( group B) for exploring the relationship between plantar-flexion load and induced muscle perfusion. In a pilot group of five elderly healthy subjects and five patients with PAD ( group C), we proposed a protocol that measured perfusion for a low-intensity exercise and for an exhaustion exercise in a single MRI session. In group A, perfusion estimates for calf muscles were highly reproducible, with correlation coefficients of 0.90-0.93. In group B, gastrocnemius perfusion increased linearly with the exercise workload ( P < 0.05). With the low-intensity exercise, patients with PAD in group C showed substantially lower gastrocnemius perfusion compared with elderly healthy subjects [43.4 (SD 23.5) vs. 106.7 (SD 73.2) ml·min-1·100 g-1]. With exhaustion exercise, G/S [1.0 (SD 0.4)] for patients with PAD was lower than both its low-intensity level [1.9 (SD 1.3)] and the level in elderly healthy subjects [2.7 (SD 2.1)]. In conclusion, the proposed MRI protocol and the new metrics are feasible for quantifying exercise-induced muscle hyperemia, a promising functional test of PAD. NEW & NOTEWORTHY To quantitatively map exercise-induced hyperemia in calf muscles, we proposed a high-resolution MRI method shown to be highly reproducible and sensitive to exercise load. With the use of low contrast, it is feasible to measure calf muscle hyperemia for both low-intensity and exhaustion exercises in a single MRI session. The newly proposed metrics for interpreting perfusion maps are promising for quantifying intermuscle vascular redistribution or a muscle's active hyperemia.

Sampling arterial input function (AIF) from peripheral arteries: Comparison of a temporospatial-feature based method against conventional manual method.

It is often difficult to accurately localize small arteries in images of peripheral organs, and even more so with vascular abnormality vasculatures, including collateral arteries, in peripheral artery disease (PAD). This poses a challenge for manually sampling arterial input function (AIF) in quantifying dynamic contrast-enhanced (DCE) MRI data of peripheral organs. In this study, we designed a multi-step screening approach that utilizes both the temporal and spatial information of the dynamic images, and is presumably suitable for localizing small and unpredictable peripheral arteries. In 41 DCE MRI datasets acquired from human calf muscles, the proposed method took <5 s on average for sampling AIF for each case, much more efficient than the manual sampling method; AIFs by the two methods were comparable, with Pearson's correlation coefficient of 0.983 ±â€¯0.004 (p-value < 0.01) and relative difference of 2.4% ±â€¯2.6%. In conclusion, the proposed temporospatial-feature based method enables efficient and accurate sampling of AIF from peripheral arteries, and would improve measurement precision and inter-observer consistency for quantitative DCE MRI of peripheral tissues.

Diagnostic Accuracy of Noncontrast MR Angiography Protocols at 3T for the Detection and Characterization of Lower Extremity Peripheral Arterial Disease.

PURPOSE: To compare the diagnostic accuracy of established non-gadolinium (Gd)-enhanced magnetic resonance (MR) angiography protocols with Gd-enhanced MR angiography at 3T for evaluating lower extremity peripheral arterial disease (PAD). MATERIALS AND METHODS: From February 2014 to 2015, 20 patients with PAD and intermittent claudication (16 men; age range, 51-76 y; Fontaine stage II) underwent 3-station (abdominopelvic, thigh, and calf) non-Gd MR angiography and bolus-chase Gd MR angiography protocols performed at 3T (Siemens Tim Trio), including quiescent-interval single-shot (QISS) MR angiography for all 3 stations and a combination of quadruple inversion recovery (QIR) MR angiography for the abdominopelvic station and electrocardiogram-gated fast spin echo (ECG-FSE) MR angiography for the extremities. Two radiologists independently evaluated vessel segments for vascular stenosis, diagnosis confidence, graft presence, and Trans-Atlantic Inter-Society Consensus (TASC) II classification for each station. Diagnostic accuracies and κ agreement were assessed. RESULTS: Of 573 vascular segments imaged, 16.9% (97/573, 19/20 patients) demonstrated hemodynamically significant abnormalities. Reader confidence was sufficient for diagnosis in 98% of segments with Gd MR angiography, 93% with QIR/ECG-FSE, and 95% with QISS. Overall reader confidence was higher with QISS than QIR/ECG-FSE within all 3 stations combined (P < .05). With low-confidence segments treated as misdiagnosis, sensitivity, specificity, positive predictive value, negative predictive value, accuracy, and κ agreement for all 3 stations combined were 81.4/87.2/57.0/95.8/86.2%/0.578 for QIR/ECG-FSE and 75.0/90.6/61.6/94.7/88.0%/0.597 for QISS. Using TASC II criteria to assess severity, QISS and QIR/ECG-FSE had no statistical difference in agreement with Gd MR angiography. CONCLUSIONS: QISS and QIR/ECG-FSE MR angiography protocols demonstrate comparable diagnostic accuracies with high specificity. Either protocol provides an alternative to Gd MR angiography at 3T for patients with PAD.

Isolated avulsion fracture of the first metatarsal base at the peroneus longus tendon attachment: a case report.

Avulsion fractures of the first metatarsal (MT1) base at the peroneus longus (PL) tendon attachment are rare and may be undiagnosed during an emergency visit. If the injury is not treated properly, chronic pain or persistent impairment for inversion and plantar-flexion of the first ray may occur. This case report presents a 30-year-old woman who presented 10 weeks post trauma to a foot and ankle surgeon due to a swollen right midfoot with diffuse tenderness over the medial Lisfranc joint. Further evaluation showed an isolated avulsion fracture of the first metatarsal, which was undiagnosed during the emergent visit following the accident. In this case, the patient was successfully treated conservatively. The goal of this article is to raise awareness of this rare injury for radiologists and orthopedic surgeons.