Neuromuscular imaging in inherited muscle diseases - PubMed (original) (raw)

Review

Neuromuscular imaging in inherited muscle diseases

Mike P Wattjes et al. Eur Radiol. 2010 Oct.

Abstract

Driven by increasing numbers of newly identified genetic defects and new insights into the field of inherited muscle diseases, neuromuscular imaging in general and magnetic resonance imaging (MRI) in particular are increasingly being used to characterise the severity and pattern of muscle involvement. Although muscle biopsy is still the gold standard for the establishment of the definitive diagnosis, muscular imaging is an important diagnostic tool for the detection and quantification of dystrophic changes during the clinical workup of patients with hereditary muscle diseases. MRI is frequently used to describe muscle involvement patterns, which aids in narrowing of the differential diagnosis and distinguishing between dystrophic and non-dystrophic diseases. Recent work has demonstrated the usefulness of muscle imaging for the detection of specific congenital myopathies, mainly for the identification of the underlying genetic defect in core and centronuclear myopathies. Muscle imaging demonstrates characteristic patterns, which can be helpful for the differentiation of individual limb girdle muscular dystrophies. The aim of this review is to give a comprehensive overview of current methods and applications as well as future perspectives in the field of neuromuscular imaging in inherited muscle diseases. We also provide diagnostic algorithms that might guide us through the differential diagnosis in hereditary myopathies.

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Figures

Fig. 1

Fig. 1

Ultrasound images of the quadriceps muscle in normal control (a) and a patient with Duchenne muscular dystrophy (b). In the healthy subject (a), muscle appears largely black with few perimysial septa. Note the increased homogeneous fine granular echogenicity of muscle due to increased replacement of normal muscle by connective and fatty tissue in the patient with muscular dystrophy (b)

Fig. 2

Fig. 2

Transverse T1-weighted (upper row) and spectral fat-suppressed T2-weighted MR image (bottom row) of the thighs of a 48-year-old woman presenting with myotonic dystrophy type 1. Note the different degrees of fatty degeneration within the gastrocnemius muscle. The medial head shows an end-stage fatty degeneration (grade 4 according to the Mercuri and Fischer scale, grade 3 according to the Kornblum scale, Table 1). The muscle tissue is completely replaced by fat. The lateral head shows a moth-eaten appearance with scattered small areas of increased signal (fatty degeneration grade 2 according to the rating scales established by Mercuri et al., Kornblum et al. and Fischer et al., Table 1). The fat-suppressed T2-weighted image shows a high signal in the medial head of the gastrocnemius muscle indicating oedema because of inflammatory changes before and during the degenerative disease stages

Fig. 3

Fig. 3

Transverse spectral fat-suppressed T2-weighted images obtained from two patients presenting with a myotonic dystrophy type 1 (A: 37-year-old woman; B: 16-year-old boy). The images were obtained during a multi-sequence whole-body muscle MRI protocol. In both patients, dilatation of the oesophagus in the proximal segment with the air-fluid level could be diagnosed, which was clinically reflected by dysphagia

Fig. 4

Fig. 4

Flowchart showing the approach to LGMD. Most LGMD patients have greater affliction of the posterior rather than the anterior thigh compartment muscles. On the other hand, patients with dystrophinopathy and sarcoglycanopathy often have significant affliction of the quadriceps muscle. Dystrophinopathy often presents with early and marked changes in the gastrocnemii muscles, while patients with sarcoglycanopathy show no affliction of these muscles. Patients with dysferlinopathy most often show posterior thigh and posterior lower leg involvement with sparing of the sartorius, gracilis and biceps femoris. However, muscle affection can be variable, but clinically calf atrophy and absence of scapular winging are commonly present. Calpain-3 and FKRP patients present with predominant posterior thigh and posterior lower leg involvement. Calpain-3 patients usually show marked involvement of the soleus and medial gastrocnemius muscles. Furthermore, calf atrophy and scapular winging are usually observed. Conversely, FKRP patients have a more diffuse involvement of the posterior lower leg muscles, while the tibial anterior muscle is often spared or even hypertrophied

Fig. 5

Fig. 5

Muscle imaging differences in myofibrillar myopathies. Highly specific and sensitive statistical criteria were identified in a systematic retrospective muscle imaging assessment in a large series of 43 MFM patients [24]. Equal or greater affliction of the semitendinosus than the biceps femoris and equal or greater affliction of the peroneal group than the tibial anterior muscles is highly specific for primary desminopathy and crystallinopathy (18 out of 19 patients). Those of the remaining patients who had equal or greater involvement of the sartorius than the semi-tendinosus and equal or greater involvement of the adductor magnus than the gracilis usually had a myotilin mutation (eight out of nine patients). All eight patients who did not fulfil the criteria for desmin and myotilin mutations and who had more involvement of the medial than the lateral gastrocnemius showed a filamin C mutation. Two of the three remaining patients had a ZASP and the third a myotilin mutation

Fig. 6

Fig. 6

Muscle MRI of lower extremities in other muscular dystrophies. Myotonic dystrophy type I (a) is typically characterised by distal more than proximal muscle involvement showing predominant affliction of the soleus, medial gastrocnemius and proximally the anterior thigh compartment with relative sparing of the rectus femoris. Patients with myotonic dystrophy type II (or proximal myotonic myopathy = PROMM) (b) are often less affected and show no fatty degeneration. Affected patients show more involvement of the proximal muscles with affliction of the quadriceps and sparing of the rectus femoris and gracilis muscles. FSHD (c) patients are often characterised by marked asymmetry with the adductor magnus, hamstrings, rectus femoris and tibial anterior being the most frequently affected muscles. OPMD (d) patients show predominantly posterior thigh (adductor magnus, semimembranosus and biceps femoris muscles) and posterior lower leg (soleus) muscle involvement

Fig. 7

Fig. 7

Flowchart showing a useful approach to the differential diagnosis of congenital myopathies. We highly recommend systematically analysing muscle imaging findings beginning with the thigh muscles. The first distinction should be made according to the relation of posterior to anterior thigh muscle involvement. Most CMs show greater affliction of the posterior rather than the anterior thigh muscles. In the second step, the same relation should be assessed in the lower legs. Predominant posterior thigh and posterior lower leg involvement with sparing of the gracilis and sartorius but marked affliction of the soleus and medial gastrocnemius is observed in DNM2-CNM. Predominantly posterior thigh with marked affliction of the sartorius and predominantly diffuse posterior lower leg involvement are typical findings of SEPN1-related CM. Posterior thigh but anterior leg involvement was observed in CM patients with ACTA1 mutations. On the other hand, marked anterior thigh affliction is seen in RYR1- and collagen 6A-related CM. In addition, RYR1 patients show sparing of the rectus femoris, gracilis and biceps femoris and often marked affliction of the soleus muscle, while patients with a collagen 6A defect show a special rim with the beginning of degeneration within the rectus femoris muscle and a degenerative rim between the soleus und gastrocnemius muscles. Typical muscle imaging findings of patients with proven mutations in the DNM2, SEPN1, ACTA1, RYR1 and collagen 6A1 are provided

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