- Email: [email protected]
Magnetic Resonance Imaging Findings in Acquired Myopathy
Images
Magnetic Resonance Imaging Findings in Acquired Myopathy Se Won Lee, MD, Margarita Manahan, MD, Naman Goel, MD, Dennis D. J. Kim, MD The magnetic resonance imaging (MRIs) presented in this report highlight the characteristic features of various acquired myopathies. MRI is particularly valuable because it can be used to assess not only the site and severity of skeletal muscle pathologies but also surrounding structures such as subcutaneous tissues. The following 2 cases, briefly reported, demonstrate the role of MRI in supporting the clinical and electrophysiological findings. An 85-year-old woman was admitted to our hospital with insidious onset of bilateral shoulder pain, swelling, and weakness for 2 weeks. Physical examination revealed 3⫹ pitting edema with tenderness in the whole arm, forearm, and hand bilaterally. On manual muscle testing, shoulder abduction/flexion was 2/5, elbow flexion 4/5, finger flexion 4/5, hip flexion 4/5, and knee flexion/extension and ankle dorsiflexion/plantarflexion 5/5. Laboratory workup revealed an increased creatine phosphokinase measurement of 1676. MRI of the left shoulder and upper extremity showed extensive edema pattern affecting the anterior and posterior muscle compartments of the arm and shoulder girdle (Figure 1). Needle electromyography of proximal limbs and paraspinal muscles revealed fibrillation and positive sharp waves with small-amplitude, shortduration motor units and early recruitment bilaterally. These findings, combined with increased creatine phosphokinase level and MRI findings, were consistent with acquired inflammatory myopathy, either polymyositis or dermatomyositis. A 36-year-old man with a history of hypertension and uncontrolled insulin-dependent diabetes mellitus presented with worsening pain, swelling, and weakness in the right thigh. Needle electromyography (EMG) examination revealed a discrete area of small-amplitude, short-duration motor unit potentials with early recruitment in the right vastus medialis suggesting focal myopathic process. MRI revealed decreased signal in the nidus surrounded by increased signal in T2-weighted and short tau inversion recovery (STIR) images in the vastus medialis and adductor muscles consistent with muscle infarction/necrosis (Figure 2). Diabetic muscle infarction (DMI) was suspected in light of the patient’s uncontrolled diabetes and negative hypercoagulability study findings. The differential diagnosis for a painful limb edema includes deep vein thrombosis, traumatic hematoma, pseudoaneurysm, arteriovenous fistula, abscess, soft-tissue tumors, compartment syndrome, polymyalgia rheumatica, and acquired myopathies, to name a few. [1] MRI has an important role in the evaluation of both soft-tissue pathologies and muscle abnormalities, as demonstrated in the aforementioned cases. Myopathy is a common cause of muscle edema. It is characterized as high signal intensity on T2-weighted images with selective fat suppression or STIR sequences in the active phase. On the basis of the pattern of distribution, myopathy can be classified as having a diffuse, focal, or multifocal pattern. Diffuse patterns include polymyositis and dermatomyositis, which involve proximal distribution symmetrically, or inclusion body myositis, which involves more distal distribution asymmetrically. The involvement of subcutaneous connective tissue septa and muscle fascia favors dermatomyositis. In the chronic phase, fatty atrophy of the musculature is seen as increased signal intensity and decreased muscle mass in the T1-weighted images. A focal muscle edema pattern can be attributed to necrotizing fasciitis, pyomyositis, DMI, radiation, and primary tumor [2]. Necrotizing fasciitis is seen on MRI as subcutaneous fluid and gas with nonenhancing fascia PM&R
884
1934-1482/11/$36.00 Printed in U.S.A.
S.W.L. Department of Physical Medicine and Rehabilitation, Montefiore Medical Center, Albert Einstein College of Medicine, 1600 Tenbroeck Avenue, Bronx, NY 10461. Address correspondence to S.W.L.; e-mail: [email protected] Disclosure: nothing to disclose M.M. Department of Physical Medicine and Rehabilitation, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY Disclosure: nothing to disclose N.G. Department of Physical Medicine and Rehabilitation, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY Disclosure: nothing to disclose D.D.J.K. Department of Physical Medicine and Rehabilitation, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY Disclosure: nothing to disclose Submitted for publication April 5, 2011; accepted April 26, 2011.
© 2011 by the American Academy of Physical Medicine and Rehabilitation Vol. 3, 884-885, September 2011 DOI: 10.1016/j.pmrj.2011.04.027
PM&R
Vol. 3, Iss. 9, 2011
885
[3]. The presence of a focal, rim-enhancing collection within the area of muscle edema in contrast-enhanced MRI is a hallmark of pyomyositis [4]. DMI most commonly affects the thigh [5] and is characterized by nonenhancing areas after contrast, reflecting underlying necrosis with high signal intensity within muscle groups on T2-weighted images. In conclusion, MRI is useful in demonstrating the softtissue and muscular changes found in patients with acquired myopathy presenting as painful limb edema.
Figure 2. T2-weighted sagittal (A), axial (B), and short tau inversion recovery (STIR) axial view (C) of right thigh revealed increased signal intensity in the vastus medialis and adductor muscles (arrowheads) with focal central nidus (arrows).
REFERENCES
Figure 1. T2-weighted sagittal and short tau inversion recovery (STIR) coronal and axial images of the left upper extremity showing pattern of edema that involves muscles of the shoulder girdle (arrow in B) as well as the anterior and posterior compartments of the arm (arrow in C). The arrow in (A) indicates the corresponding level of axial view in (C).
1. Useche JN, de Castro AM, Galvis GE, Mantilla RA, Ariza A. Use of US in the evaluation of patients with symptoms of deep venous thrombosis of the lower extremities. Radiographics 2008;28:1785-1797. 2. Yildirim Donmez F, Feldman F. Muscle compromise in diabetes. Acta Radiol 2008;49:673-679. 3. Schmid MR, Kossmann T, Duewell S. Differentiation of necrotizing fasciitis and cellulitis using MR imaging. AJR Am J Roentgenol 1998;170:615-620. 4. McMahon CJ, Wu JS, Eisenberg RL. Muscle edema. AJR Am J Roentgenol 2010;194:W284-W292. 5. Trujillo-Santos AJ. Diabetic muscle infarction: An underdiagnosed complication of long-standing diabetes. Diabetes Care 2003;26:211-215.
Magnetic Resonance Imaging Findings in Acquired Myopathy Se Won Lee, MD, Margarita Manahan, MD, Naman Goel, MD, Dennis D. J. Kim, MD The magnetic resonance imaging (MRIs) presented in this report highlight the characteristic features of various acquired myopathies. MRI is particularly valuable because it can be used to assess not only the site and severity of skeletal muscle pathologies but also surrounding structures such as subcutaneous tissues. The following 2 cases, briefly reported, demonstrate the role of MRI in supporting the clinical and electrophysiological findings. An 85-year-old woman was admitted to our hospital with insidious onset of bilateral shoulder pain, swelling, and weakness for 2 weeks. Physical examination revealed 3⫹ pitting edema with tenderness in the whole arm, forearm, and hand bilaterally. On manual muscle testing, shoulder abduction/flexion was 2/5, elbow flexion 4/5, finger flexion 4/5, hip flexion 4/5, and knee flexion/extension and ankle dorsiflexion/plantarflexion 5/5. Laboratory workup revealed an increased creatine phosphokinase measurement of 1676. MRI of the left shoulder and upper extremity showed extensive edema pattern affecting the anterior and posterior muscle compartments of the arm and shoulder girdle (Figure 1). Needle electromyography of proximal limbs and paraspinal muscles revealed fibrillation and positive sharp waves with small-amplitude, shortduration motor units and early recruitment bilaterally. These findings, combined with increased creatine phosphokinase level and MRI findings, were consistent with acquired inflammatory myopathy, either polymyositis or dermatomyositis. A 36-year-old man with a history of hypertension and uncontrolled insulin-dependent diabetes mellitus presented with worsening pain, swelling, and weakness in the right thigh. Needle electromyography (EMG) examination revealed a discrete area of small-amplitude, short-duration motor unit potentials with early recruitment in the right vastus medialis suggesting focal myopathic process. MRI revealed decreased signal in the nidus surrounded by increased signal in T2-weighted and short tau inversion recovery (STIR) images in the vastus medialis and adductor muscles consistent with muscle infarction/necrosis (Figure 2). Diabetic muscle infarction (DMI) was suspected in light of the patient’s uncontrolled diabetes and negative hypercoagulability study findings. The differential diagnosis for a painful limb edema includes deep vein thrombosis, traumatic hematoma, pseudoaneurysm, arteriovenous fistula, abscess, soft-tissue tumors, compartment syndrome, polymyalgia rheumatica, and acquired myopathies, to name a few. [1] MRI has an important role in the evaluation of both soft-tissue pathologies and muscle abnormalities, as demonstrated in the aforementioned cases. Myopathy is a common cause of muscle edema. It is characterized as high signal intensity on T2-weighted images with selective fat suppression or STIR sequences in the active phase. On the basis of the pattern of distribution, myopathy can be classified as having a diffuse, focal, or multifocal pattern. Diffuse patterns include polymyositis and dermatomyositis, which involve proximal distribution symmetrically, or inclusion body myositis, which involves more distal distribution asymmetrically. The involvement of subcutaneous connective tissue septa and muscle fascia favors dermatomyositis. In the chronic phase, fatty atrophy of the musculature is seen as increased signal intensity and decreased muscle mass in the T1-weighted images. A focal muscle edema pattern can be attributed to necrotizing fasciitis, pyomyositis, DMI, radiation, and primary tumor [2]. Necrotizing fasciitis is seen on MRI as subcutaneous fluid and gas with nonenhancing fascia PM&R
884
1934-1482/11/$36.00 Printed in U.S.A.
S.W.L. Department of Physical Medicine and Rehabilitation, Montefiore Medical Center, Albert Einstein College of Medicine, 1600 Tenbroeck Avenue, Bronx, NY 10461. Address correspondence to S.W.L.; e-mail: [email protected] Disclosure: nothing to disclose M.M. Department of Physical Medicine and Rehabilitation, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY Disclosure: nothing to disclose N.G. Department of Physical Medicine and Rehabilitation, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY Disclosure: nothing to disclose D.D.J.K. Department of Physical Medicine and Rehabilitation, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY Disclosure: nothing to disclose Submitted for publication April 5, 2011; accepted April 26, 2011.
© 2011 by the American Academy of Physical Medicine and Rehabilitation Vol. 3, 884-885, September 2011 DOI: 10.1016/j.pmrj.2011.04.027
PM&R
Vol. 3, Iss. 9, 2011
885
[3]. The presence of a focal, rim-enhancing collection within the area of muscle edema in contrast-enhanced MRI is a hallmark of pyomyositis [4]. DMI most commonly affects the thigh [5] and is characterized by nonenhancing areas after contrast, reflecting underlying necrosis with high signal intensity within muscle groups on T2-weighted images. In conclusion, MRI is useful in demonstrating the softtissue and muscular changes found in patients with acquired myopathy presenting as painful limb edema.
Figure 2. T2-weighted sagittal (A), axial (B), and short tau inversion recovery (STIR) axial view (C) of right thigh revealed increased signal intensity in the vastus medialis and adductor muscles (arrowheads) with focal central nidus (arrows).
REFERENCES
Figure 1. T2-weighted sagittal and short tau inversion recovery (STIR) coronal and axial images of the left upper extremity showing pattern of edema that involves muscles of the shoulder girdle (arrow in B) as well as the anterior and posterior compartments of the arm (arrow in C). The arrow in (A) indicates the corresponding level of axial view in (C).
1. Useche JN, de Castro AM, Galvis GE, Mantilla RA, Ariza A. Use of US in the evaluation of patients with symptoms of deep venous thrombosis of the lower extremities. Radiographics 2008;28:1785-1797. 2. Yildirim Donmez F, Feldman F. Muscle compromise in diabetes. Acta Radiol 2008;49:673-679. 3. Schmid MR, Kossmann T, Duewell S. Differentiation of necrotizing fasciitis and cellulitis using MR imaging. AJR Am J Roentgenol 1998;170:615-620. 4. McMahon CJ, Wu JS, Eisenberg RL. Muscle edema. AJR Am J Roentgenol 2010;194:W284-W292. 5. Trujillo-Santos AJ. Diabetic muscle infarction: An underdiagnosed complication of long-standing diabetes. Diabetes Care 2003;26:211-215.