Skeletal muscle disease: patterns of MRI appearances

Abstract

Although the presumptive diagnosis of skeletal muscle disease (myopathy) may be made on the basis of clinical-radiological correlation in many cases, muscle biopsy remains the cornerstone of diagnosis. Myopathy is suspected when patients complain that the involved muscle is painful and tender, when they experience difficulty performing tasks that require muscle strength or when they develop various systemic manifestations. Because the cause of musculoskeletal pain may be difficult to determine clinically in many cases, MRI is increasingly utilised to assess the anatomical location, extent and severity of several pathological conditions affecting muscle. Infectious, inflammatory, traumatic, neurological, neoplastic and iatrogenic conditions can cause abnormal signal intensity on MRI. Although diverse, some diseases have similar MRI appearances, whereas others present distinct patterns of signal intensity abnormality. In general, alterations in muscle signal intensity fall into one of three cardinal patterns: muscle oedema, fatty infiltration and mass lesion. Because some of the muscular disorders may require medical or surgical treatment, correct diagnosis is essential. In this regard, MRI features, when correlated with clinical and laboratory findings as well as findings from other methods such as electromyography, may facilitate correct diagnosis. This article will review and illustrate the spectrum of MRI appearances in several primary and systemic disorders affecting muscle, both common and uncommon. The aim of this article is to provide radiologists and clinicians with a collective, yet succinct and useful, guide to a wide array of myopathies.

Rectus Abdominis Rhabdomyolysis: Report of 2 Cases

“…Magnetic resonance imaging has widely been advocated as the reference standard for confirming rhabdomyolysis because of its exceptional contrast resolution and a reported sensitivity rate of 100% . Sensitivity rates for other modalities fair less favorably, with literature suggesting that computed tomography and sonography have sensitivity rates of 62% and 42%, respectively .…”

Clinics in diagnostic imaging (179)

“…Muscle abnormalities may be broadly classified into three patterns: muscle oedema, fatty infiltration and mass lesion. (5,6) MR imaging has superior soft-tissue contrast resolution and the highest sensitivity among the different imaging modalities available for the detection of rhabdomyolysis. (7,8) Diffuse T2-weighted hyperintensity with corresponding T1-weighted hypointensity in the affected muscle groups, the most common finding described on MR imaging, represents diffuse oedema.…”

“…(11,12) In the absence of relevant clinical history and laboratory markers, radiological findings of rhabdomyolysis may be difficult to distinguish from those of inflammatory myopathy, muscle infection, necrotising fasciitis or other conditions associated with myonecrosis such as diabetes mellitus or sickle cell crisis. (5,6,9,(13)(14)(15)(16)(17)(18) Nonetheless, certain clinical clues and radiological patterns may help to guide imaging interpretation. For example, inflammatory myopathies secondary to autoimmune causes, such as polymyositis or dermatomyositis, usually present with slowly progressive onset of weakness and classically involve the symmetrical proximal muscles, which appear hyperintense on fluid-sensitive sequences (e.g.…”

Acute myonecrosis on MRI: etiologies in an oncological cohort and assessment of interobserver variability

“…Type 2 changes, due to irreversible muscle necrosis, demonstrate predominantly heterogeneous signal intensity and rim enhancement, as well as the stipple sign [5, 6]. Due to its high soft tissue contrast, MRI is considered the best noninvasive method to identify necrotic muscle [4, 8, 15]. The diagnosis of acute myonecrosis in our study, as well as in our daily clinical practice, was based predominantly on the stipple sign described in type 2 rhabdomyolysis [5, 6]: enhancing foci within a region of muscle surrounded by rim enhancement.…”