MR Imaging of Atraumatic Muscle Disorders

Imaging spectrum of atraumatic muscle disorders: a radiologist's guide

Atraumatic muscle disorders comprise a very wide range of skeletal muscle diseases, including metabolic, inflammatory, autoimmune, infectious, ischemic, and neoplastic involvement of the muscles. Therefore, one must take clinical and laboratory data into consideration to elucidate the differential diagnoses, as well as the distribution of the muscle compromise along the body-whether isolated or distributed along the body in a symmetric or asymmetrical fashion. Assessment of muscular disorders often requires imaging investigation before image-guided biopsy or more invasive procedures; therefore, radiologists should understand the advantages and limitations of imaging methods for proper lesion evaluation and be aware of the imaging features of such disorders, thus contributing to proper decision-making and good patient outcomes. In this review, we propose a systematic approach for the assessment of muscle disorders based on their main imaging presentation, dividing them into patterns that can be easily recognized.

Off the wall: incidental paraspinal and pelvic muscle pathology on abdominopelvic imaging

As the use of cross-sectional abdominal and pelvic imaging has increased exponentially in the past several decades, incidental musculoskeletal findings have become commonplace. These are often unrelated to the indication for the examination and are frequently referred to as the "radiologist's blind spot" on these studies. The differential diagnosis for abnormalities of the paraspinal and pelvic musculature is, in many cases, quite different from the anterior abdominal wall muscles. Furthermore, due to their relatively deep location, pathology involving the former muscle groups is more likely to be clinically occult, often presenting only incidentally when the patient undergoes cross-sectional imaging. Effective treatment of diseases of these muscles is dependent on adherence to a diverse set of diagnostic and treatment algorithms. The purpose of this review article is to familiarize the radiologist with the unique pathology of these often-overlooked muscles of the abdomen and pelvis.

Autoimmune diseases of the spine and spinal cord

Magnetic resonance imaging (MRI) and clinicopathological tools have led to the identification of a wide spectrum of autoimmune entities that involve the spine. A clearer understanding of the unique imaging features of these disorders, along with their clinical presentations, will prove invaluable to clinicians and potentially limit the need for more invasive procedures such as tissue biopsies. Here, we review various autoimmune diseases affecting the spine and highlight salient imaging features that distinguish them radiologically from other disease entities.

Pseudolesions involving bone and soft tissue regarding orthopedic oncology

Pseudolesions in bone and muscle are encountered mostly incidentally in routine imaging studies, especially due to the recent advancements on many different imaging modalities. These lesions can be categorized into the following categories: normal variants; congenital; iatrogenic; degenerative; and postoperative. In this review, we discuss the many different radiological characteristics of musculoskeletal pseudolesions that appear on imaging, which can prevent non-essential additional studies.

Sarcopenia Among Older People in the Philippines: A Scoping Review

Aims: This review aimed to identify and map the evidence about sarcopenia among older Filipinos. Methods: Studies about sarcopenia among Filipinos aged 60 and above were included. All studies regardless of type, setting, language, and timeframe were reviewed. The Cochrane Library, Cumulative Index of Nursing and Allied Health, Embase, PubMed, and Health Research and Development Information Network were searched. The study was conducted per an a priori protocol and utilized the Joanna Briggs Institute guidance for scoping reviews. Results: From the 87 records identified, 20 studies published from 2013 to 2023 were eligible (≥ 5424 participants). The studies were varied; 11 cross-sectional, 2 conference lectures, 2 consensus reports, 1 meta-analysis, cohort study, case series, posthoc analysis, and continuing education. As to setting, 11 studies were conducted in the hospital and 4 in the community. On the level of prevention, 5 studies addressed the primary level, 10 studies secondary, and 2 studies both tertiary and secondary. The studies focused on: sarcopenia in a specific group (13 studies), consensus (4 studies), and education (3 studies). Conclusions: Sarcopenia studies among older Filipinos were limited. Most were hospital-based and involved patients with comorbidities. Some studies used sarcopenia assessment guidelines with Filipino normative references. Sarcopenia impacts the overall well-being of older Filipinos; hence more studies and health promotion programs are necessary.

Rhabdomyolysis: a review of imaging features across modalities

This review illustrates the imaging features of rhabdomyolysis across multiple modalities and in a variety of clinical scenarios. Rhabdomyolysis is the rapid breakdown of striated muscle following severe or prolonged insult resulting in the release of myocyte constituents into circulation. In turn, patients develop characteristically elevated serum creatine kinase, positive urine myoglobin, and other serum and urine laboratory derangements. While there is a spectrum of clinical symptoms, the classic presentation has been described as muscular pain, weakness, and dark urine. This triad, however, is only seen in about 10% of patients. Thus, when there is a high clinical suspicion, imaging can be valuable in evaluating the extent of muscular involvement, subsequent complications such as myonecrosis and muscular atrophy, and other etiologies or concurrent injuries causing musculoskeletal swelling and pain, especially in the setting of trauma. Sequela of rhabdomyolysis can be limb or life-threatening including compartment syndrome, renal failure, and disseminated intravascular coagulation. MRI, CT, ultrasound, and 18-FDG PET/CT are useful modalities in the evaluation of rhabdomyolysis.

Society of skeletal radiology position paper - recommendations for contrast use in musculoskeletal MRI: when is non-contrast imaging enough?

The following White Paper will discuss the appropriateness of gadolinium administration in MRI for musculoskeletal indications. Musculoskeletal radiologists should consider the potential risks involved and practice the judicious use of intravenous contrast, restricting administration to cases where there is demonstrable added value. Specific nuances of when contrast is or is not recommended are discussed in detail and listed in table format. Briefly, contrast is recommended for bone and soft tissue lesions. For infection, contrast is reserved for chronic or complex cases. In rheumatology, contrast is recommended for early detection but not for advanced arthritis. Contrast is not recommended for sports injuries, routine MRI neurography, implants/hardware, or spine imaging, but is helpful in complex and post-operative cases.

Musculoskeletal manifestations of COVID-19

During the COVID-19 pandemic, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infected millions of people worldwide, with acute respiratory distress syndrome (ARDS) being the most common severe condition of pulmonary involvement. Despite its involvement in the lungs, SARS-CoV-2 causes multiple extrapulmonary manifestations, including manifestations in the musculoskeletal system. Several cases involving bone, joint, muscle, neurovascular and soft tissues were reported shortly after pandemic onset. Even after the acute infection has resolved, many patients experience persistent symptoms and a decrease in quality of life, a condition known as post-COVID syndrome or long COVID. COVID-19 vaccines have been widely available since December 2020, preventing millions of deaths during the pandemic. However, adverse reactions, including those involving the musculoskeletal system, have been reported in the literature. Therefore, the primary goal of this article is to review the main imaging findings of SARS-CoV-2 involvement in the musculoskeletal system, including acute, subacute, chronic and postvaccination manifestations.

Swelling of the Muscles of the Shoulder Girdle in a CT Scan is a Leading Finding for the Diagnosis of Polymyositis

Polymyositis (PM) is an uncommon inflammatory disease of unknown cause, but the disease shares many characteristics with autoimmune disorders. In the past, the diagnosis criteria for PM depended primarily on clinical features, blood enzyme levels, an electromyogram, and muscle biopsies. However, there are still imperfections in the diagnostic criteria of PM. The development of muscle imaging led to revisiting not only the PM diagnosis strategy but also the patients' follow-up. Teaching point: PM should be considered and included in the differential diagnosis of a patient with inflammatory signs and muscular pain, and the radiologist should be aware of its imaging features.

Lumbrical muscle enhancement on MRI and its association with rheumatoid arthritis

OBJECTIVE

To investigate the significance of lumbrical muscle enhancement (LME) on magnetic resonance imaging (MRI) in rheumatoid arthritis (RA).

MATERIALS AND METHODS

Blinded to the diagnoses, contrast-enhanced bilateral hand MRIs of patients with suspected early RA between 2014 and 2019 were reviewed by two observers for the presence and degree (weak/strong) of LME. The presence of other inflammatory findings was also noted. The patients were then stratified into RA (n = 41), control (n = 31), and other arthritides groups(n = 28) based on their final diagnoses in the hospital records within the following 12 months. Categorical variables were compared by chi-square test or Fisher's exact test. Differences among the groups were evaluated by one-way ANOVA or Kruskal-Wallis tests. When the p-value from the Kruskal-Wallis test was statistically significant, multiple comparison test was used to identify group differences. Correlations between LME and flexor tenosynovitis were evaluated by Spearman rank correlation test. The agreement between two observers was assessed by Cohen's Kappa (κ) statistic. P-value < 0.05 was considered as statistically significant.

RESULTS

There were 100 patients (88 females) with mean age of 47.2 ± 11.2. There were no significant differences for age or sex between groups (p = 0.17, p = 0.84, respectively). RA patients showed significantly more frequent (p < 0.001) and stronger LME (p = 0.001). There were no correlations between LME and flexor tenosynovitis (p > 0.05). Interrater agreement for the degree of LME on right and left sides was substantial (κ = 0.74, κ = 0.67, respectively).

CONCLUSION

RA patients demonstrated significantly more frequent and stronger LME with substantial interrater agreement. LME could constitute a subtle radiological clue for early RA.

Complications of Cancer Therapy in Children: A Comprehensive Review of Body Imaging Findings

ABSTRACT

Complications of cancer therapy in children can result in a spectrum of toxicities that can affect any organ system and result in a range of morbidity. Complications may occur at the initiation of therapy or years following treatment. Although childhood cancer remains rare, increasing survival rates means more children are living longer following their treatment. Radiologists often play an important role in the diagnosis and evaluation of these complications, and thus, awareness of their imaging findings is essential to guide management and avoid misdiagnosis. This second part of a 2-part review aims to illustrate the typical body imaging findings of cancer therapy-related toxicities, including both early and late treatment effects. The article also discusses the differential diagnosis of imaging findings, highlighting pearls and pitfalls in making the appropriate diagnosis.

Levothyroxine use and longitudinal changes in thigh muscles in at-risk participants for knee osteoarthritis: preliminary analysis from Osteoarthritis Initiative cohort

BACKGROUND

We examined the association between levothyroxine use and longitudinal MRI biomarkers for thigh muscle mass and composition in at-risk participants for knee osteoarthritis (KOA) and their mediatory role in subsequent KOA incidence.

METHODS

Using the Osteoarthritis Initiative (OAI) data, we included the thighs and corresponding knees of participants at risk but without established radiographic KOA (baseline Kellgren-Lawrence grade (KL) < 2). Levothyroxine users were defined as self-reported use at all annual follow-up visits until the 4th year and were matched with levothyroxine non-users for potential confounders (KOA risk factors, comorbidities, and relevant medications covariates) using 1:2/3 propensity score (PS) matching. Using a previously developed and validated deep learning method for thigh segmentation, we assessed the association between levothyroxine use and 4-year longitudinal changes in muscle mass, including cross-sectional area (CSA) and muscle composition biomarkers including intra-MAT (within-muscle fat), contractile percentage (non-fat muscle CSA/total muscle CSA), and specific force (force per CSA). We further assessed whether levothyroxine use is associated with an 8-year risk of standard KOA radiographic (KL ≥ 2) and symptomatic incidence (incidence of radiographic KOA and pain on most of the days in the past 12 months). Finally, using a mediation analysis, we assessed whether the association between levothyroxine use and KOA incidence is mediated via muscle changes.

RESULTS

We included 1043 matched thighs/knees (266:777 levothyroxine users:non-users; average ± SD age: 61 ± 9 years, female/male: 4). Levothyroxine use was associated with decreased quadriceps CSAs (mean difference, 95%CI: - 16.06 mm²/year, - 26.70 to - 5.41) but not thigh muscles' composition (e.g., intra-MAT). Levothyroxine use was also associated with an increased 8-year risk of radiographic (hazard ratio (HR), 95%CI: 1.78, 1.15-2.75) and symptomatic KOA incidence (HR, 95%CI: 1.93, 1.19-3.13). Mediation analysis showed that a decrease in quadriceps mass (i.e., CSA) partially mediated the increased risk of KOA incidence associated with levothyroxine use.

CONCLUSIONS

Our exploratory analyses suggest that levothyroxine use may be associated with loss of quadriceps muscle mass, which may also partially mediate the increased risk of subsequent KOA incidence. Study interpretation should consider underlying thyroid function as a potential confounder or effect modifier. Therefore, future studies are warranted to investigate the underlying thyroid function biomarkers for longitudinal changes in the thigh muscles.

Early shoulder-girdle MRI findings in severe COVID-19-related intensive care unit-acquired weakness: a prospective cohort study

OBJECTIVE

To describe clinical and early shoulder-girdle MR imaging findings in severe COVID-19-related intensive care unit-acquired weakness (ICU-AW) after ICU discharge.

METHODS

A single-center prospective cohort study of all consecutive patients with COVID-19-related ICU-AW from November 2020 to June 2021. All patients underwent similar clinical evaluations and shoulder-girdle MRI within the first month and then 3 months (± 1 month) after ICU discharge.

RESULTS

We included 25 patients (14 males; mean [SD] age 62.4 [12.5]). Within the first month after ICU discharge, all patients showed severe proximal predominant bilateral muscular weakness (mean Medical Research Council total score = 46.5/60 [10.1]) associated with bilateral, peripheral muscular edema-like MRI signals of the shoulder girdle in 23/25 (92%) patients. At 3 months, 21/25 (84%) patients showed complete or quasi-complete resolution of proximal muscular weakness (mean Medical Research Council total score > 48/60) and 23/25 (92%) complete resolution of MRI signals of the shoulder girdle, but 12/20 (60%) patients experienced shoulder pain and/or shoulder dysfunction.

CONCLUSIONS

Early shoulder-girdle MRI findings in COVID-19-related ICU-AW included muscular edema-like peripheral signal intensities, without fatty muscle involution or muscle necrosis, with favorable evolution at 3 months. Precocious MRI can help clinicians distinguish critical illness myopathy from alternative, more severe diagnoses and can be useful in the care of patients discharged from intensive care with ICU-AW.

KEY POINTS

• We describe the clinical and shoulder-girdle MRI findings of COVID-19-related severe intensive care unit-acquired weakness. • This information can be used by clinicians to achieve a nearly specific diagnosis, distinguish alternative diagnoses, assess functional prognosis, and select the more appropriate health care rehabilitation and shoulder impairment treatment.

Spectrum of imaging findings in soft-tissue necrosis

Soft tissue necrosis can occur at different tissue levels, with numerous underlying causes. In this pictorial review, we highlight myonecrosis, and its accompanying stages, fat necrosis, devitalized soft tissue seen with infection, and necrotizing soft tissue infections. Imaging examples are provided with each entity.

Post-COVID-19 Myositis Based on Magnetic Resonance Imaging: A Case Report

The severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) causes COVID-19, which is known to cause fever, dry cough, exhaustion, headache, and loss of taste and smell. Although fever, sore throat, and cough have historically been the utmost characteristic symptoms of the illness, published case reports have recently started to emphasize additional uncommon and unusual presentations of infection with the coronavirus. In COVID, the musculoskeletal system is seldomly involved. In addition to reviewing the causes and imaging characteristics of COVID-19-related illnesses of the musculoskeletal system, we elaborate on a case of a middle-aged man who developed myositis as sequelae to the COVID-19 infection.

The Musculoskeletal Manifestations of COVID-19: A Narrative Review Article

The coronavirus pandemic has caused a devastating impact across the planet. Millions of lives lost and economic structures are struggling to remain afloat. Clinical effects of SARS CoV-2 virus include tiredness, fatigue, headache, cough, loss of appetite, fever, loss of sensations of taste, and smell as well as other respiratory difficulties. Pulmonary complications of coronavirus infections result in severe pneumonia with the final sequelae being sepsis, and end-stage respiratory failure. Further cardiovascular, neurological, hematological, and gastrointestinal complications build up to cause the demise of the immune system ultimately leading to death of the affected individual. The attack of the virus and the resultant reaction of the epithelial cells lining the respiratory tract have been in the limelight of most studies pertaining to the pandemic. However, a lesser number of studies have detailed the muscular and osseous pathologies that appear post-coronavirus infection. Inflammation post-infection, across the organ systems, may appear as a link to bone and joint pathology. Myalgia is a typical COVID-19 infection symptom. On the contrary, other musculoskeletal signs have very seldom been reported. Multimodality imaging techniques stand a chance at showing the diagnosis and the degree of follow-up after evaluation. Apart from myalgia, there are cases of arthralgia, myopathies, and neuropathies. According to numerous reports, there is the possibility of a link between the current drug regimen used to treat the SARS-CoV-2 infection and the musculoskeletal manifestations observed. In this study, we aim to shed light on the coronavirus pandemic and its association to various musculoskeletal manifestations, provide a different perspective of the infected patients, and address the major points that a clinician must take care while administering care to the patient. We will also address the present treatment in line with the various musculoskeletal symptoms observed.

Imaging Features of Soft Tissue Tumor Mimickers: A Pictorial Essay

Soft tissue lesions are commonly encountered and imaging is an important diagnostic step in the diagnosis and management of these lesions. While some of these lesions are true neoplasms, others are not. These soft tissue tumor mimickers can be due to a variety of conditions including traumatic, iatrogenic, inflammatory/reactive, infection, vascular, and variant anatomy. It is important for the radiologist and clinician to be aware of these common soft tissue tumor mimickers and their characteristic imaging features to avoid unnecessary workup and provide the best treatment outcome.

Imaging More than Skin-Deep: Radiologic and Dermatologic Presentations of Systemic Disorders

Background: Cutaneous manifestations of systemic diseases are diverse and sometimes precede more serious diseases and symptomatology. Similarly, radiologic imaging plays a key role in early diagnosis and determination of the extent of systemic involvement. Simultaneous awareness of skin and imaging manifestations can help the radiologist to narrow down differential diagnosis even if imaging findings are nonspecific. Aims: To improve diagnostic accuracy and patient care, it is important that clinicians and radiologists be familiar with both cutaneous and radiologic features of various systemic disorders. This article reviews cutaneous manifestations and imaging findings of commonly encountered systemic diseases. Conclusions: Familiarity with the most disease-specific skin lesions help the radiologist pinpoint a specific diagnosis and consequently, in preventing unnecessary invasive workups and contributing to improved patient care.

Deep vein thrombosis in the thigh: MR imaging in two cases with atypical presentations

Deep vein thrombosis (DVT) is a common clinical problem affecting the lower extremities. Prompt imaging of suspected DVT is helpful for rapid diagnosis and proper treatment. However, patients without clear predisposing factors for DVT may be directed to alternative diagnoses of a musculoskeletal disorder. The few case reports and studies of magnetic resonance (MR) imaging of unsuspected DVT are limited to the calf and knee. Here, we report two cases with a rare presentation of thigh MR imaging of unsuspected DVT. Identifying branching, abnormal intraluminal signals on fluid-sensitive imaging, or rim-enhancing tubular structures within the edema of the thigh muscle is important for differentiating intramuscular DVT from other thigh pathologies.

Low-velocity, civilian firearm extremity injuries-review and update for radiologists

Firearm injuries are a preventable epidemic in the USA. Extremities are commonly affected in gunshot injuries. Such injuries may be complex with concomitant osseous, soft tissue, and neurovascular components. The maximum wounding potential of a projectile is determined by its kinetic energy and the proportion of the kinetic energy that is transmitted to the target. Accurate assessment of ballistic injuries is dependent on utilizing the principles of wound ballistics, accurate bullet count, and ballistic trajectory analysis. The goals of this article are to review wound ballistics and the imaging evaluation of extremity civilian firearm injuries in the adult population, with emphasis on ballistic trajectory analysis, specific ballistic fracture patterns, and diffuse, secondary soft tissue ballistic injuries.

MRI Findings in Case of Post-COVID-19 Vaccination Rhabdomyolysis: A Rare Postvaccination Adverse Effect

In the era of this pandemic, without any proper and efficacious availability of antiviral agents against the novel coronavirus disease 2019 (COVID-19), vaccines have come as a hope for humankind. Although adverse reactions are common after getting the COVID-19 vaccine, serious or life-threatening side effects are very uncommon in these new emergency-approved vaccines. In this case report, we describe an unusual case of adverse reaction in a patient who received the COVID-19 vaccination. The patient who received the COVID-19 vaccination presented with progressive right lower limb pain and swelling, which further progressed to bilateral shoulder pain and swelling. Ultrasonography, Doppler, and magnetic resonance imaging of right lower limb were done for the patient.

A Muscle Biosignature Differentiating Between Limb-Girdle Muscular Dystrophy and Idiopathic Inflammatory Myopathy on Magnetic Resonance Imaging

Background: The overlapping clinical presentations of limb-girdle muscular dystrophy (LGMD) and idiopathic inflammatory myopathy (IIM) make clinical diagnosis challenging. This study provides a comprehensive evaluation of the distributions and characteristics of muscle fat substitution and edema and aims to differentiate those two diseases.

Methods: This retrospective study reviewed magnetic resonance imaging (MRI) of seventeen patients with pathologically proved diagnosis, comprising 11 with LGMD and 6 with IIM. The fat-only and water-only images from a Dixon sequence were used to evaluate muscle fat substitution and edema, respectively. The degrees of muscle fat substitution and edema were graded and compared using the appropriate statistical methods.

Results: In LGMD, more than 50% of patients had high-grade fat substitution in the majority of muscle groups in the thigh and calf. However, <50% of IIM patients had high-grade fat substitution in all muscle groups. Moreover, LGMD patients had significantly higher grade fat substitution than IIM patients in all large muscle groups (p < 0.05). However, there was no significant difference in edema in the majority of muscle groups, except the adductor magnus (p = 0.012) and soleus (p = 0.009) with higher grade edema in IIM. Additionally, all the adductor magnus muscles in LGMD (100%) showed high-grade fat substitution, but none of them showed high-grade edema.

Conclusions: MRI could be a valuable tool to differentiate LGMD from IIM based on the discrepancy in muscle fat substitution, and the adductor magnus muscle could provide a biosignature to categorizing LGMD.

Myotendinous pseudomasses: an imaging review

A mass or a tumor may not always be an underlying cause for a clinically apparent swelling. A wide range of myotendinous disorders can present as pseudomasses. These include muscle/myofascial hernia, tendon tears, benign hypertrophy, accessory muscles, tendon xanthomas, diffuse myositis, and exertional compartment syndromes. We have briefly reviewed these lesions highlighting their typical radiological findings and have also highlighted the role of different imaging modalities and the role of dynamic imaging. Although rare, radiologists should be aware of these entities to avoid mislabeling a pseudomass as a mass or malignancy and to detect the abnormality in not-so-apparent masses.

MR imaging findings of musculoskeletal involvement in microscopic polyangiitis: a comparison with inflammatory myopathy

OBJECTIVE

The purpose of this study was to evaluate the importance of MR imaging findings of musculoskeletal involvement of the lower limbs in diagnosing microscopic polyangiitis (MPA) vs polymyositis (PM) or dermatomyositis (DM).

MATERIALS AND METHODS

This study included 13 patients diagnosed with MPA clinically and through histologically, and 38 diagnosed with PM/DM, who underwent MR imaging of the lower limbs prior to treatment. Axial and coronal short tau inversion recovery (STIR) images were reviewed retrospectively.

RESULTS

The sites affected by MPA were the lower legs in six (46%) patients and the thighs in seven (54%). Intramuscular hyperintensity and fascial hyperintensity were observed in all cases of MPA (100%). Fascial hyperintensity was more frequently encountered in MPA than in PM/DM (100% vs. 45%, p < 0.01). As the predominantly involved sites, the fascial regions were more frequently affected by MPA than by PM/DM (77% vs. 18%, p < 0.01). Diffuse subcutaneous fat hyperintensity was more frequently observed in MPA than in PM/DM (100% vs. 16%, p < 0.01). However, no significant differences in intramuscular hyperintensity (100% vs. 97%, p = 0.745) and subcutaneous fat hyperintensity (54% vs. 50%, p = 0.533) were found between MPA and PM/DM.

CONCLUSION

Intramuscular hyperintensity and fascial hyperintensity have always been observed in MPA, and the predominantly affected sites were usually the fascial regions. Compared with PM/DM, fascial hyperintensity and diffuse subcutaneous fat hyperintensity were more frequent in MPA.

Myositis in a patient with coronavirus disease 2019: A rare presentation

The world is presently struggling with coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A patient with COVID-19 typically presents with fever, non-productive cough, dyspnea, and myalgia. A 49-year-old female presented with complaints of subacute onset and progressive symmetrical proximal muscle weakness of both upper limbs and lower limbs with no sensory, cranial nerve deficit. She had elevated creatine phosphokinase levels of 906 U/L, an aspartate aminotransferase level of 126 IU/L, a lactate dehydrogenase level of 354 U/L, and an erythrocyte sedimentation rate of 68 mm/1 hr, and magnetic resonance imaging of the pelvis and thigh revealed muscle edema suggestive of myositis. Her reverse transcriptase-polymerase chain reaction result for SARS-CoV-2 was positive. Her evaluation for other causes of myositis was negative. She was managed with intravenous immunoglobulins and supportive care. She showed rapid improvement in symptoms and motor weakness. To our knowledge, this is the first reported case of COVID-19 related disabling myositis in India.

Imaging review of normal anatomy and pathological conditions involving the popliteus

Popliteus is an integral component of the posterolateral corner of the knee. We review the anatomy and various pathologies affecting the popliteus.

Multidisciplinary approach to L3/L4 lumbar disc prolapse masquerading as focal limb myositis-a radiological challenge

Prolapsed intervertebral discs are commonly associated with back ache and sciatica. Management is often conservative with analgesia and physiotherapy. Nerve root injections and discectomy procedures are used where conservative measures fail. Majority of patients present with symptoms of pain and motor weakness; however, a few can present as focal myositis of lower limb muscles in the distribution of radiculopathy. MRI scans of limbs are rarely done in these cases but if done can confound the radiologist. Our case report emphasize the importance of multidisciplinary approach for a L3 nerve radiculopathy with confounding clinical presentation of focal lower limb myositis of unknown etiology.

Radiologic Definition of Sarcopenia in Chronic Liver Disease

Sarcopenia is prevalent in patients with chronic liver disease, and affected patients tend to have worse clinical outcomes and higher mortality. However, relevant analyses are limited by heterogeneity in the definition of sarcopenia and in the methodological approaches in assessing it. We reviewed several radiologic methods for sarcopenia in patients with chronic liver disease. Dual energy X-ray absorptiometry (DXA) can measure muscle mass, but it is difficult to evaluate muscle quality using this technique. Computed tomography, known as the gold standard for diagnosing sarcopenia, enables the objective measurement of muscle quantity and quality. The third lumbar skeletal muscle index (L3 SMI) more accurately predicted the mortality of subjects than the psoas muscle index (PMI). Few studies have evaluated the sarcopenia of chronic liver disease using ultrasonography and magnetic resonance imaging, and more studies are needed. Unification of the measurement method and cut-off value would facilitate a more systematic and universal prognosis evaluation in patients with chronic liver disease.

Radiologic Definition of Sarcopenia in Chronic Liver Disease

Sarcopenia is prevalent in patients with chronic liver disease, and affected patients tend to have worse clinical outcomes and higher mortality. However, relevant analyses are limited by heterogeneity in the definition of sarcopenia and in the methodological approaches in assessing it. We reviewed several radiologic methods for sarcopenia in patients with chronic liver disease. Dual energy X-ray absorptiometry (DXA) can measure muscle mass, but it is difficult to evaluate muscle quality using this technique. Computed tomography, known as the gold standard for diagnosing sarcopenia, enables the objective measurement of muscle quantity and quality. The third lumbar skeletal muscle index (L3 SMI) more accurately predicted the mortality of subjects than the psoas muscle index (PMI). Few studies have evaluated the sarcopenia of chronic liver disease using ultrasonography and magnetic resonance imaging, and more studies are needed. Unification of the measurement method and cut-off value would facilitate a more systematic and universal prognosis evaluation in patients with chronic liver disease.

A case of statin-associated immune-mediated necrotizing myopathy with atypical biopsy features

Statin-associated immune-mediated necrotizing myopathy (IMNM) is a rare presentation of a statin-associated myopathy. Patients usually present with muscle weakness and pain in the setting of statin use with elevated creatine kinase (CK) levels and a positive anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (anti-HMGCR) antibody. Muscle biopsies typically show necrosis, CD68+ macrophages, and minimal lymphocytes. We present a case of a 67-year-old woman who had 2 months of progressive weakness and bilateral lower extremity pain after initiating atorvastatin therapy with symptoms persisting after statin cessation. She was found to have high anti-HMGCR antibody titers, and the biopsy of the rectus femoris muscle showed a prominent endomysial inflammatory cell infiltrate with necrotic and regenerative fibers and an atypical extensive inflammatory infiltrate composed of both CD4+ helper T cells and CD8+ cytotoxic T cells. She showed symptom resolution and normalization of CK levels and inflammatory markers with treatment involving a prolonged prednisone taper and a brief course of azathioprine, which was stopped because of the adverse effects.

Musculoskeletal involvement of COVID-19: review of imaging

The global pandemic of coronavirus disease 2019 (COVID-19) has revealed a surprising number of extra-pulmonary manifestations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. While myalgia is a common clinical feature of COVID-19, other musculoskeletal manifestations of COVID-19 were infrequently described early during the pandemic. There have been emerging reports, however, of an array of neuromuscular and rheumatologic complications related to COVID-19 infection and disease course including myositis, neuropathy, arthropathy, and soft tissue abnormalities. Multimodality imaging supports diagnosis and evaluation of musculoskeletal disorders in COVID-19 patients. This article aims to provide a first comprehensive summary of musculoskeletal manifestations of COVID-19 with review of imaging.

Muscle Imaging

Evaluation and characterization of skeletal muscle pathology is a frequently encountered indication for musculoskeletal imaging. Causes of muscle pathology are diverse and include traumatic, autoimmune, infectious, inflammatory, neurologic, and neoplastic. Each etiology while dramatically different in the pathophysiology may present with similar imaging features. An understanding of the subtle differences in imaging features between the pathologic conditions may serve to guide diagnosis and treatment in these often complex cases. In this section, we will discuss the various skeletal muscle pathologies and the imaging features associated with each.

MRI T2/STIR epaxial muscle hyperintensity in some dogs with intervertebral disc extrusion corresponds to histologic patterns of muscle degeneration and inflammation

Magnetic resonance imaging hyperintensity on T2-weighted turbo SE and STIR sequences of the paraspinal musculature in canine patients being imaged for thoracolumbar intervertebral disc extrusion is frequently observed but poorly understood in veterinary medicine. The objective of this prospective analytical study was to describe the histopathology of muscle hyperintensity in dogs with thoracolumbar intervertebral disc extrusions and to determine if a relationship exists between the presence of this hyperintensity and various patient factors. Twenty privately owned dogs who underwent surgical decompression of intervertebral disc extrusions diagnosed on MRI were enrolled (10 normal "control or nonaffected cases" without MRI paraspinal musculature hyperintensity and 10 "affected cases" with hyperintensity). Surgical biopsies of the epaxial musculature at the region of hyperintensity (affecteds) and at the site of the disc herniation (controls) were submitted for histopathology. The degree of myofiber degeneration and necrosis was scored using an ordinal scoring system: absent (0), minimal (10), mild (20), moderate (30), marked/severe (40), and massive (50). Associations between hyperintensity presence and patient age, weight, body condition, neurologic status, acuteness of onset, number of disc herniation sites, degree of spinal cord compression, and volume of herniated material were investigated. Nonaffected patients were significantly older (median age = 9.4 years) than affected patients (median age = 3.5 years), but no other significant associations were found. Acute myofiber degeneration/necrosis and intramuscular inflammation were observed in half of affected patients. Therefore, T2/STIR muscle hyperintensity in some patients with intervertebral disc extrusion may represent muscle degeneration and inflammation.

Retrobulbar and Tongue Base Pyogranulomatous Myositis Resulting in Strabismus in a Dog: Case Report

A seven-year-old female spayed Australian Shepherd was presented for a 3-day history of left eye ventromedial strabismus, episcleral injection, protrusion of the third eyelid, miosis, and enophthalmia. Magnetic Resonance Imaging (MRI) identified lesions in the left medial pterygoid muscle and left tongue base. Cytology and histopathology revealed pyogranulomatous inflammation with rod-shaped bacteria and pyogranulomatous myositis, respectively. One month of oral antibiotics resolved both lesions. Repeat MRI showed a mild decrease in size of the left medial pterygoid muscle consistent with fibrosis. Clinically, residual, positional ventral strabismus remained upon dorsal neck extension, but all other ophthalmic abnormalities resolved. To the authors' knowledge, this is the first report of pyogranulomatous myositis causing this constellation of clinical signs and of repeat imaging depicting resolution of these lesions with therapy.

Diagnostic utility of perilesional muscle edema in myositis ossificans

OBJECTIVES

To investigate the value of extensive perilesional muscle edema for the differentiation between myositis ossificans (MO) and malignant intramuscular soft tissue tumors on MRI.

MATERIALS AND METHODS

Two blinded readers analyzed MR examinations of 90 consecutive patients with intramuscular soft tissue masses (group 1: MO, n = 20; group 2: malignant tumors, n = 70). Extent of edema around lesions was graded (0, none; 1, minimal edema; 2, moderate edema; 3, extensive edema). Edema-lesion ratio (ELR = ratio of the maximal diameter of the edema and the maximal diameter of the central lesion) was calculated. ROC analysis, Mann-Whitney U test, and Kappa test were used.

RESULTS

A total of 70% and 60% of patients with MO had edema grade 3 (reader 1/reader 2), 30%/40% edema grade 2. For the patients with malignant tumors, it was 2.9%/1.4% (edema grade 3) and 16%/23% (edema grade 2). Interrater reliability was substantial (kappa = 0.66). Extent of edema was significantly higher for patients of group 1 (p < 0.0001, both readers). Mean ELR was 3.60 (group 1) and 1.35 (group 2), with statistically significant differences (p < 0.0001). Grade 3 edema showed a sensitivity/specificity of 70%/97.1% (reader 1) and 60%/99% (reader 2) for diagnosing MO. For ELR > 2.0, sensitivity was 90% and specificity 91% for diagnosing MO.

CONCLUSIONS

Extensive perilesional muscle edema on MRI of more than double the size of the central lesion is highly specific, but not pathognomonic for myositis ossificans in the early/intermediate stage in the differentiation to malignant intramuscular soft tissue lesions.

Glossary of terms for musculoskeletal radiology

Members of the International Skeletal Society compiled a glossary of terms for musculoskeletal radiology. The authors also represent national radiology or pathology societies in Asia, Australia, Europe, and the USA. We provide brief descriptions of musculoskeletal structures, disease processes, and syndromes and address their imaging features. Given the abundance of musculoskeletal disorders and derangements, we chose to omit most terms relating to neoplasm, spine, intervention, and pediatrics. Consensus agreement was obtained from 19 musculoskeletal radiology societies worldwide.

Characterization of intramuscular calf vein thrombosis on routine knee MRI

OBJECTIVE

Literature regarding intramuscular calf vein thrombosis (IMCVT) or infrapopliteal deep vein thrombosis (DVT) evaluation by magnetic resonance imaging (MRI) is limited, particularly with regard to routine unenhanced knee examinations. We attempt to correlate routine unenhanced MRI findings with ultrasound evaluations of the lower extremity deep venous system.

MATERIALS AND METHODS

The radiology information system was searched, yielding a total of 67 patients who had undergone both routine knee MRI and duplex ultrasound examinations within 14 days. The MRI examination findings recorded were the presence and pattern of edema, segmental vein dilation, intraluminal signal on fluid-sensitive sequences, and abnormal hyperintense signal on axial T1-weighted sequences. The presence and extent of thrombus more centrally (i.e., intramuscular calf vein thrombosis with or without extension into the popliteal vein) was reassessed on ultrasound.

RESULTS

When comparing patients with positive (n = 13) and negative (n = 54) ultrasound, there were significant differences in each of these parameters: perivascular edema, intramuscular edema, focal vein dilation, and abnormal fluid-sensitive signal. In the subset of patients with popliteal extension of the intramuscular calf vein thrombosis compared with those without any deep vein thrombosis, there was a statistically significant increase in peripopliteal edema, abnormal fluid-sensitive signal, and abnormal hyperintense T1 signal.

CONCLUSION

Imaging findings on routine unenhanced MRI have a high rate of concordance with duplex ultrasound performed through the calf in the detection of intramuscular calf vein thrombosis.

Colchicine Myopathy: A Case Series Including Muscle MRI and ABCB1 Polymorphism Data

Colchicine is a medication most commonly used in the treatment of gout and familial mediterannean fever. A rare complication of therapy is toxicity causing proximal myopathy and polyneuropathy. Colchicine myopathy has been associated with the coadministration of other medications with colchicine, such as statins or tacrolimus, and is more common in patients with renal impairment. Otherwise, it is unclear which patients are at greatest risk of developing this adverse drug reaction. ABCB1 is important to the metabolism of colchicine, so we speculated that it was possible that colchicine myopathy patients may have a particular genotype that is associated with this side effect. We describe two cases of colchicine myopathy which occurred with co-administration of rosuvastatin. From one case, we present the first published data on muscle MRI in this condition. We additionally present an analysis of four genetic polymorphisms in ABCB1 and transcript levels in muscle tissue, and demonstrate the descriptive finding of reduced ABCB1 transcript levels in the colchicine myopathy patients.

Diagnostic Imaging of Inflammatory Myopathies: New Concepts and a Radiological Approach

PURPOSE OF REVIEW

The purpose of this review article is to highlight the current role of diagnostic imaging in the assessment of inflammatory myopathies.

RECENT FINDINGS

Recent research demonstrates that imaging plays an important role in evaluating patients with symptoms of an inflammatory myopathy. In general, MRI is the pivotal imaging modality for assessing inflammatory myopathies, revealing precise anatomic details because of changes in the signal intensity of the muscles. Whole-body MR imaging has become increasingly important over the last several years. US is also a valuable imaging modality for scanning muscles. Together with the clinical history, familiarity with the imaging features of inflammatory myopathies is essential for formulating an accurate diagnosis.

Detecting Toxic Myopathies as Medication Side Effect

The goal of this article is to provide physiatrists, neurologists, and neuromuscular medicine physicians a framework that can be easily used in the process of evaluating, identifying, and treating patients with toxic myopathies. This review attempts to classify these rare but potentially deadly conditions in clinical patterns and distinguishes the cellular mechanisms in which the offending agents tend to impact the structure and function of myocytes.

Fasciae of the musculoskeletal system: normal anatomy and MR patterns of involvement in autoimmune diseases

Abstract

The fascial system is a three-dimensional continuum of connective tissues present everywhere throughout the body, from the head to the toes and from the skin to the bone. The current article aims to review the normal anatomy of the fasciae of the musculoskeletal system with macroscopic and microscopic correlations and to describe their appearance at MRI in normal subjects and in patients with autoimmune diseases of the musculoskeletal system.

Key Points

• The fascial system is a three-dimensional continuum of connective tissues.

• It is present everywhere throughout the body, from the head to the toes and from the skin to the bone.

• The normal fascial system is barely visible at MRI.

• MR patterns of fascial involvement in autoimmune diseases reflect the complex anatomy of the fasciae of the musculoskeletal system.