Pattern Of Muscle Involvement Research Articles

EP23 Symptomatic sarcoid myopathy: a rare extra-pulmonary manifestation of sarcoidosis

EP23 Symptomatic sarcoid myopathy: a rare extra-pulmonary manifestation of sarcoidosis

MUSCLE IMAGING – MRI: P.162 The use of muscle MRI in the diagnosis of neuromuscular diseases

Inherited neuromuscular disorders (NMD) are a heterogeneous group of disorders characterized by progressive muscle weakness, different pattern of muscle involvement, age of onset. Thanks to next generation sequencing the numbers of genes responsible for NMD is growing. In recent years muscle MRI has contributed to the diagnosis of NMD by evaluating the selective pattern of muscle involvement. We retrospectively reviewed the muscle MRI of 533 individuals (age 5-93 years) performed at the John Walton muscular dystrophy research centre in Newcastle.

Deep phenotyping of facioscapulohumeral muscular dystrophy type 2 by magnetic resonance imaging.

The aim was to define the radiological picture of facioscapulohumeral muscular dystrophy 2 (FSHD2) in comparison with FSHD1 and to explore correlations between imaging and clinical/molecular data. Upper girdle and/or lower limb muscle magnetic resonance imaging scans of 34 molecularly confirmed FSHD2 patients from nine European neuromuscular centres were analysed. T1-weighted and short-tau inversion recovery (STIR) sequences were used to evaluate the global pattern and to assess the extent of fatty replacement and muscle oedema. The most frequently affected muscles were obliquus and transversus abdominis, semimembranosus, soleus and gluteus minimus in the lower limbs; trapezius, serratus anterior, latissimus dorsi and pectoralis major in the upper girdle. Iliopsoas, popliteus, obturator internus and tibialis posterior in the lower limbs and subscapularis, spinati, sternocleidomastoid and levator scapulae in the upper girdle were the most spared. Asymmetry and STIR hyperintensities were consistent features. The pattern of muscle involvement was similar to that of FSHD1, and the combined involvement of trapezius, abdominal and hamstring muscles, together with complete sparing of iliopsoas and subscapularis, was detected in 91% of patients. Peculiar differences were identified in a rostro-caudal gradient, a predominant involvement of lower limb muscles compared to the upper girdle, and in the higher percentage of STIR hyperintensities in FSHD2. This multicentre study defines the pattern of muscle involvement in FSHD2, providing useful information for diagnostics and clinical trial design. Both similarities and differences between FSHD1 and FSHD2 were detected, which is also relevant to better understand the pathogenic mechanisms underlying the FSHD-related disease spectrum.

Quantitative Imaging in Muscle Diseases with Focus on Non-proton MRI and Other Advanced MRI Techniques.

The role of neuromuscular imaging in the diagnosis of inherited and acquired muscle diseases has gained clinical relevance. In particular, magnetic resonance imaging (MRI), especially whole-body applications, is increasingly being used for the diagnosis and monitoring of disease progression. In addition, they are considered as a powerful outcome measure in clinical trials. Because many muscle diseases have a distinct muscle involvement pattern, whole-body imaging can be of diagnostic value by identifying this pattern and thus narrowing the differential diagnosis and supporting the clinical diagnosis. In addition, more advanced MRI applications including non-proton MRI, diffusion tensor imaging, perfusion MRI, T2 mapping, and magnetic resonance spectroscopy provide deeper insights into muscle pathophysiology beyond the mere detection of fatty degeneration and/or muscle edema. In this review article, we present and discuss recent data on these quantitative MRI techniques in muscle diseases, with a particular focus on non-proton imaging techniques.

Qualitative and quantitative muscle ultrasound in patients with Duchenne muscular dystrophy: Where do sonographic changes begin?

The number of studies investigating and understanding the disease mechanisms of Duchenne muscular dystrophy (DMD) in human clinical trials have increased substantially over the last decade. Suitable clinical instruments for the measurement of disease progress and drug efficiency are mandatory, but currently not available, especially in the youngest patients. The aim of this study was to detect a reproducible pattern of muscle involvement in early stages potentially preceding evidence of motor regression. A cohort of 25 DMD patients aged 1-6yearsat the first presentation were examined at multiple timepoints and compared with age-matched healthy controls. Muscle ultrasound was quantified using computer-analyzed gray scale levels (GSL) and blinded visual rating, using a modified Heckmatt scale. Changes in muscle echogenicity in DMD patients occurred very early, clearly preceding motor regression and in some cases, even before the motor plateau phase was reached. Visual rating and GSL identified the earliest changes in the proximal adductor magnus muscle. Muscle ultrasound can be used as an additional method to assess the disease progression and for decision-making in paucisymptomatic DMD patients. Sonographic changes in the ad-ductor magnus muscle seem to be the first detectable changes with a recognisable pattern.

Phenotypic correlations in a large single-center cohort of patients with BSCL2 nerve disorders: a clinical, neurophysiological and muscle magnetic resonance imaging study.

BSCL2 heterozygote mutations are a common cause of distal hereditary motor neuropathies (dHMNs). A series of BSCL2 patients is presented and clinical, neurophysiological and muscle magnetic resonance imaging (MRI) findings are correlated. Twenty-six patients from five families carrying the p.N88S mutation were identified. Age of onset, clinical phenotype (dHMN, Charcot-Marie-Tooth, spastic paraplegia), physical examination, disability measured as a modified Rankin Scale score and neurophysiological findings were collected. A whole body muscle MRI had been performed in 18 patients. The pattern of muscle involvement on T1-weighted and short time inversion recovery sequences was analysed. Hierarchical analysis using heatmaps and an MRI Composite Score were generated. Statistical analysis was carried out with STATA SE v.15 (TX, USA). The mean age was 51.54±19.94years and 14 patients were men. dHMN was the most common phenotype (50%) and five patients (19.23%) showed no findings on examination. Disease onset was commonly in childhood and disability was low (modified Rankin Scale score 1.34±1.13) although median time since onset of disease was 32years (range10-47). Charcot-Marie-Tooth-like patients were more disabled and disability correlated with age. On muscle MRI, thenar eminence, soleus and tibialis anterior were most frequently involved, irrespective of clinical phenotype. MRI Composite Score was strongly correlated with disability. Patients with the p.N88S BSCL2 gene mutation are phenotypically variable, although dHMN is most frequent and generally slowly progressive. Muscle MRI pattern is consistent regardless of phenotype and correlates with disease severity, probably serving as a reliable outcome measure for future clinical trials.

Characteristic muscle signatures assessed by quantitative MRI in patients with Bethlem myopathy.

Using MRI, the main aim was to (1) map the pattern of muscle involvement by assessing fat fraction and (2) investigate frequency of target and sandwich signs in 42 muscles of patients with Bethlem myopathy (BM). Fifteen BM patients were included. Results were compared to findings in 8 healthy controls and 50 patients with four other types of muscular dystrophies. All muscles, except one, showed higher fat fraction in BM patients vs healthy controls (p < 0.05) with an overall proximal muscle affection, resembling a limb girdle-like pattern. In moderate patients, the specificity was 90% for the sandwich sign and 98% for the target sign. Sensitivity for both signs was 100%. Twelve BM patients had sandwich sign in other muscles than the vastus lateralis. Muscle strength correlated with fat fraction. Mean fat fraction in the psoas major was 39% in BM patients, which was considerably higher than in 3 of the 4 muscular dystrophy control diseases. The presence of signs in conjunction with severe affection of the psoas major muscle can serve as a diagnostic tool in BM. The high level of STIR lesions in muscles of BM patients warrants further investigations.

MRI pattern changes in pelvic muscle and lower limb in patients with dysferlinopathy

Introduction . Dysferlinopathy is a phenotypically heterogeneous group of hereditary muscular dystrophies caused by mutations in the dysferlin gene ( DYSF ). Debut in adolescence, predominantly in physically developed patients, combined with the often subacute development of hypercreatine phosphatemia and edematous muscle changes in MRI often leads to diagnostic errors. Purpose of the study : to determine the most typical MRI pattern of muscle damage of the pelvic girdle and lower limb in patients with dysferlinopathy. Materials and methods . 40 people were examined, among which 20 patients with a clinical picture of dysferlinopathy with an equal ratio of Miyoshi phenotypes and LGMD and an average age of 35 (24; 44) years. Comprehensive clinical and instrumental examination included neurological, electroneuromyographic and molecular genetic studies (NGS). Magnetic resonance imaging of the muscles of the pelvic girdle and lower limb was performed in 20 patients and a control group equivalent in sex and age. Results . The use of semi-quantitative MRI indicators — relative signal intensity — D (D=T1 muscle (STIR) / T1 (STIR) subcutaneous fat layer) made it possible to formulate the characteristics of a common typical MRI pattern of muscle involvement in dysferlinopathy. An increase in the intensity of the relative signal D, T1 in the rear muscle group of the thighs and lower legs, indicating fatty infiltration was observed most frequently, while a decrease in D, STIR values was observed in the anterior and medial muscles of the thighs, reflecting the presence of edema of the previous fatty degeneration of these muscles. Conclusion . In addition to the general idea of muscle involvement in dysferlinopathy, it is advisable to consider the «early», «typical / completed» and «late» MRI patterns of dysferlinopathy that increase the effectiveness of the diagnosis of this disease. In the differential diagnosis of the Miyoshi phenotype from LGMD, one should focus on maintaining normal values of D, T1 from m. gluteus maximus and m. popliteus at all stages of the disease.

"Boule du biceps" in dysferlinopathy.

Eymard et al.1 first described “boule du biceps” (bulging of biceps), a ball-like appearance caused by the selective atrophy of the distal half of the biceps brachii (BB) muscle, in patients with dysferliniopathy. This sign is also known as biceps lump. In our cohort of 24 patients with dysferlinopathy (22 symptomatic and 2 asymptomatic hyperCKemia), all confirmed both by the absence of dysferlin on muscle biopsy and by the presence of DYSF mutation on genetic analysis, except for 4 patients who were diagnosed only at the protein level. Among the 20 patients who were genetically confirmed, 18 were homozygotes for 3 different recurrent (c.342+1G>A, c.755C>T, and c.4431G>T) and 3 different nonrecurrent (c.1958delG, c.3944\_3948delinsG, and c.5983\_5984del) mutations, and 2 were compound heterozygotes of mutations different from those in other patients (c.2190dupA/c.3597G>A and c.4101G>A/c.6124C>T, respectively). Of note, we did not try to subclassify the clinical phenotype into Miyoshi myopathy and LGMD2B/LGMD-R2 dysferlin related as recent articles suggest that there is no essential difference in the pattern of muscle involvement, and thus, they are the same disease.2–5 The BB was carefully observed during contraction and relaxation to check for the sign. The function of the upper limb (UL) was assessed using the Medical Research Council (MRC) scale. Furthermore, the BB was observed in patients with other muscular dystrophy in our cohort (DMD/BMD 118 cases, sarcoglycanopathy 12 cases, FSHD 5 cases, LGMD2A 18 cases, and other LGMDs 5 cases). Boule du biceps was observed in 71% (17/24) of our patients with dysferlinopathy, including the 2 asymptomatic ones. The UL MRC score was 4 or higher in the 17 patients who showed boule du biceps, but was 3+ or lower in the 7 patients who lacked the sign. None of the controls showed boule du biceps. MRI of the BB of the asymptomatic patient during arm flexion showed that the distal part of the short head was partially infiltrated by fat, whereas the long head and the proximal part of the short head were spared. MRI of the symptomatic patient showed moderate fat infiltration in the long head and in the distal part of the short head, whereas the proximal part of the short head was spared (figure). The sign was absent in patients with more marked muscle weakness, suggesting that even the proximal portion of the BB may be affected in the advanced stages and thus can no longer show contraction. Five of 7 patients who did not show boule du biceps were nonambulant, indicating that this sign disappears in advanced stage of the disease. Our findings suggest that the distal portion of the short head of the BB is affected even in early stages, whereas the proximal part is spared, which gives rise to boule du biceps. This can be a valuable diagnostic clinical feature for dysferlinopathy from early stages of the disease.

Electrodiagnostic Findings in 441 Patients with Ulnar Neuropathy - a Retrospective Study.

PurposeUlnar neuropathy (UN) is the second most common focal neuropathy in the upper extremities. Electrodiagnostic studies (EDx), including nerve conduction study (NCS) and electromyography (EMG), are reliable tools for the diagnosis of ulnar neuropathy. We aimed to retrospectively analyze the medical records of patients diagnosed with ulnar neuropathy in a seven-year period and report our findings.Patients and methodsIn this retrospective study, documents of the patients whose ulnar nerve injury was confirmed through electrodiagnostic study in two departments of Physical Medicine and Rehabilitation were collected and demographic data, subjective complaints of the patient, the cause, and electrodiagnostic findings were extracted from each patient’s file. The following points were specifically evaluated in the electrodiagnostic records; type of injury, location, accompanying injuries, sensory nerve action potentials (SNAP) of the fifth finger, SNAP of dorsal ulnar cutaneous nerve (DUCN), compound muscle action potential (CMAP) of abductor digiti minimi (ADM) muscle, nerve conduction velocity (NCV) across elbow, patterns of muscle involvement, and the severity of insult.ResultsOut of 441 records, 305 (69.2%) were male and 68.1% were non-traumatic. Based on our clinical criteria, the intensity of the injury was mild in most cases. The elbow and forearm were the most involved regions in non-traumatic and traumatic cases respectively. Across elbow nerve conduction velocity showed decreased velocity in 71% of records. In non-traumatic cases, the most affected muscle was ADM (97%) and then FDI (85%).ConclusionIn focal entrapments such as ulnar neuropathy, electrodiagnostic findings are very helpful in assessing location, severity, and type of injury. If a consensus is achieved for the diagnosis of UN, even retrospective studies can become valuable sources for studying UN.

MRI patterns of muscle involvement in type 2 and 3 spinal muscular atrophy patients.

Only few studies have reported muscle involvement in spinal muscular atrophy using muscle MRI but this has not been systematically investigated in a large cohort of both pediatric and adult patients with type 2 and type 3 spinal muscular atrophy. The aim of the present study was to define possible patterns of muscle involvement on MRI, assessing both fatty replacement and muscle atrophy, in a cohort of type 2 and type 3 spinal muscular atrophy children and adults (age range 2-45years), including both ambulant and non-ambulant patients. Muscle MRI protocol consisted in T1-weighted sequences acquired on axial plane covering the pelvis, the thigh, and the leg with contiguous slices. Each muscle was examined through its whole extension using a grading system that allows a semiquantitative evaluation of fatty infiltration. Thigh muscles were also grouped in anterior, posterior, and medial compartment for classification of global atrophy. The results showed a large variability in both type 2 and type 3 spinal muscular atrophy, with a various degree of proximal to distal gradient. Some muscles, such us the adductor longus and gracilis were always selectively spared. In all patients, the involvement was a combination of muscle atrophy and muscle infiltration. The variability observed may help to better understand both natural history and response to new treatments.

Functional characterization of GYG1 variants in two patients with myopathy and glycogenin-1 deficiency

Glycogen storage disease XV is caused by variants in the glycogenin-1 gene, GYG1, and presents as a predominant skeletal myopathy or cardiomyopathy.We describe two patients with late-onset myopathy and biallelic GYG1 variants. In patient 1, the novel c.144–2A>G splice acceptor variant and the novel frameshift variant c.631delG (p.Val211Cysfs*30) were identified, and in patient 2, the previously described c.304G>C (p.Asp102His) and c.487delG (p.Asp163Thrfs*5) variants were found. Protein analysis showed total absence of glycogenin-1 expression in patient 1, whereas in patient 2 there was reduced expression of glycogenin-1, with the residual protein being non-functional. Both patients showed glycogen and polyglucosan storage in their muscle fibers, as revealed by PAS staining and electron microscopy. Age at onset of the myopathy phenotype was 53 years and 70 years respectively, with the selective pattern of muscle involvement on MRI corroborating the pattern of weakness.Cardiac evaluation of patient 1 and 2 did not show any specific abnormalities linked to the glycogenin-1 deficiency. In patient 2, who was shown to express the p.Asp102His mutated glycogenin-1, cardiac evaluation was still normal at age 77 years. This contrasts with the association of the p.Asp102His variant in homozygosity with a severe cardiomyopathy in several cases with an onset age between 30 and 50 years. This finding might indicate that the level of p.Asp102His mutated glycogenin-1 determines if a patient will develop a cardiomyopathy.

Pattern of muscle involvement in dermatomyositis – A retrospective analysis using STIR MRI imaging

All patients with suspected Idiopathic Inflammatory Myopathy, over a 4 year period - from August 2014 to August 2018, seen in the departments of Neurology and Rheumatology of Aster Medcity, Kochi, India, were included in the retrospective analysis. 28 patients with DM were selected, who fulfilled the EULAR/ACR classification criteria. Of the 28 patients, 17 patients who had undergone fat suppression sequence, short tau inversion recovery (STIR) MRI muscle imaging were selected. The MRI images were collated and analysed by a single examiner who has over 4 years of experience with muscle MRI. Of the 17 patients with STIR imaging, 12 underwent a whole-body MRI and 5 underwent thigh muscle MRI only. We found that 76% patients were women, with a mean age of 48 yrs. 13 were adult DM, 3 were amyopathic DM and 1 case was a juvenile DM (9 years). The mean disease duration was 10.8 months, and the mean time to MRI from diagnosis and initiation of treatment was 4.7 months except in 3 cases who presented very late (1-2 years after onset). Most muscle changes were patchy, involving muscles asymmetrically. 70% cases showed involvement of lower limb muscles. And 30% showed upper limb and trunk muscle involvement. Paraspinal muscles and shoulder girdles were involved in 50% patients in whom whole-body MRI was performed. Interestingly, the muscles involved the most were the thigh (anterior and posterior compartment muscles), calf muscles, the glutei and pelvic muscles. The pelvic muscles were frequently involved (47%), especially obturator internus and externus.

EP.38Muscle MRI in myotonic dystrophy type 1

Disease-specific patterns of muscle involvement have been detected in several my-opathies. Only few studies reported muscle imaging data on dozens of DM1 patients. The aim of this study is to redefine the muscle involvement in a large cohort of DM1 patients and to search a correlation with clinical and genetic data. Whole body muscle MRI was obtained by more than 70 genetically confirmed DM1 patients. 33 muscle of lower limbs and 18 of upper limbs were considered. Fibrofatty replacement was established by T1 sequences, whereas inflammation was obtained by STIR sequences. Fibro-fatty replacement was more evident in lower limbs than upper limbs. Posterior compartment of the legs was the most affected district. Thighs showed a disto-proximal gradient more evident in hamstrings than in quadriceps. Muscle MRI revealed a specific pattern of muscle involvement in DM1 patients. Statistical correlation between severity of muscle involvement at MRI and clinical severity and genetical backgroud was searched.

EP.35Patterns of muscle involvement in SMA patients

EP.35Patterns of muscle involvement in SMA patients

EP.36PATCHS MRI score correlates with clinical severity in facioscapulohumeral muscular dystrophy

To find the involvement pattern of skeletal muscle in FSHD patients and its correlation with clinical evaluations. PATCHS MRI scans of multi-section muscles consist of bilateral 6 muscle groups including scapular girdle, humeral, pelvic girdle, thigh, calf and axial muscles, with a total of 78 muscles. PATCHS MRI scans in 30 Chinese FSHD1 patients were semi-quantitively assessed for fat infiltration and were correlated to multiple clinical outcome measures. Cluster analysis was conducted to identify the different involvement pattern of muscles. In scapular girdle and humeral muscle, the most frequently and severely involved muscles were the trapezius, serratus anterior, rhomboideus and latissimus dorsi. And in pelvic girdle and leg muscles, they were semimembranosus, biceps femoris, gluteus minimus and semitendinosus. The fat infiltration score of total skeletal muscles correlated highly with the motor function measure, FSHD clinical score, Ricci score, 6-minute walking test and manual muscle testing (correlation coefficients -0.8767, 0.7768, 0.7705, -0.7077, 0.6973, respectively). And the correlation was stronger in PATCHS MRI than in MRI of legs. Cluster analysis indicated two distinctive patterns of muscle involvement, suggesting a group of untypical FSHD patients with early and more severely involved pelvic girdle and leg muscles. We showed a strong correlation between the fat infiltration score of PATCHS MRI and clinical outcome measures. PATCHS MRI scans unfolded a better performance in capturing the disease severity and motor functioning comparing with MRI of legs. We identified a group of untypical FSHD patients with early and more severely involved pelvic girdle and leg muscles, indicating the wide spectrum of phenotype in FSHD.

O.20Mutations in ACTN2 gene cause a novel form of adult-onset distal myopathy

We studied three families from the same village in northern Spain and one family from Sweden with an autosomal dominant distal myopathy with rimmed vacuolar pathology. Affected members shared a very similar clinical phenotype, a characteristic pattern of muscle involvement by MRI and common histologic features. In particular, all the patients showed an adult-onset, asymmetric muscle weakness, with atrophy of tibialis anterior and initial involvement of ankle dorsiflexion later progressing to proximal limb muscles. We identified an ACTN2 c.1459T>C (p.C487R) variant co-segregating with the disease in families 1–3. An ACTN2 c.392T>C (p.L131P) variant was identified in the affected members of family 4. In all the families enrolled, the private ACTN2 variants are fully penetrant and co-segregate with the disease. ACTN2 encodes for alpha actinin2, a protein highly expressed in the Z-disk of cardiac and skeletal sarcomeres, where it plays several structural and functional roles through a complex network of interactions with other sarcomeric proteins. Our findings demonstrate that ACTN2 mutations cause a new type of dominant late-onset and slowly progressive distal myopathy. Dominant ACTN2 mutations were previously associated with hypertrophic and dilated cardiomyopathies. At the same time as our studies, two ACTN2 mutations have been described as the cause of a congenital core myopathy patients. Additional studies are needed to improve our understanding of the genotype-phenotype correlation and to clarify the molecular mechanisms of the actinopathies.

Pattern of muscle involvement according to needle electromyography findings in clinically unaffected extremities of polio survivors with lower extremity weaknesses

Amac: Paralitik poliomiyelit oykusu olan hastalarda gec donem noromuskuler kotulesme gorulebilir. Bu sorunlardan birisi, klinik olarak etkilenmemis kaslarda yeni bir gucsuzlugun gelisimidir. Bu klinik olarak etkilenmemis ekstremite kaslarindaki igne elektromyografi (EMG) bulgularini saptamayi ve poliomiyelitin fizik tedavi stratejilerine katkida bulunmayi amacladik. Yontemler: Poliomiyelit sekeli olan hastalar bu retrospektif kohort calismasina calismaya dahil edildi. Hastalarin igne EMG bulgulari gozden gecirildi. Gucsuzlugu olmayan ekstremite veya kasta norojenik igne EMG bulgulari varsa, bu kas veya ekstremite subklinik olarak etkilenmis olarak kabul edildi. Bulgular: Onsekiz hasta calismaya dahil edildi. Yuzdoksan kasin igne EMG bulgulari analiz edildi. Alt ekstremitelerde, klinik olarak etkilenmeyen 25 kasin 18'inde (%72) norojenik igne EMG bulgulari vardi, 40 ust ekstremite kasinin 14’unde (%35) subklinik tutulum mevcuttu. Alt ekstremite kaslarindaki bu subklinik tutulum, ust ekstremite kaslarina gore anlamli olarak daha fazla orandaydi (P=0,004). Klinik olarak etkilenmemis ust ve alt ekstremite kaslari icinde, en belirgin norojenik igne EMG bulgulari sirasiyla deltoid ve vastus lateralis kaslarinda idi (sirasiyla; P=0,022 ve P=0,028). Sonuc: Alt ekstremite gucsuzlugu olan polio hastalarinda subklinik tutulum alt ekstremitede ust ekstremiteden daha belirgindi. Alt ve ust ekstremitelerde en belirgin subklinik kas tutulumu sirasiyla vastus lateralis ve deltoid kaslarindaydi. Bu bulgulari dikkate alan fizik tedavi stratejilerinin polio hastalari icin faydali olacagini dusunuyoruz.

Radiographic patterns of muscle involvement in the idiopathic inflammatory myopathies.

This study assesses the burden, distribution, and evolution of muscle inflammation and damage on MRI among subtypes of idiopathic inflammatory myopathy (IIM). Musculoskeletal MRIs performed in 66 patients with IIM and 10 patients with non-IIM between 2009 and 2016 were retrospectively graded for muscle edema, fatty replacement (FR), and atrophy. Immune-mediated necrotizing myopathy (IMNM) patients had severe and extensive lower limb muscle edema, FR, and atrophy. The pelvic muscles and adductors were significantly more affected than in patients with dermatomyositis and polymyositis. Inclusion body myositis (IBM) was characterized by marked anterior thigh involvement, which stabilized or progressed at follow-up imaging. Atrophy and FR grades improved over time in some non-IBM IIM patients. Patients with IMNM and IBM have characteristic patterns of muscle MRI abnormalities that may allow them to be differentiated radiologically from other IIM subtypes. Muscle damage in non-IBM IIM may be reversible.

Skeletal muscle MRI differentiates SBMA and ALS and correlates with disease severity.

ObjectiveTo investigate the use of muscle MRI for the differential diagnosis and as a disease progression biomarker for 2 major forms of motor neuron disorders: spinal bulbar muscular atrophy (SBMA) and amyotrophic lateral sclerosis (ALS).MethodsWe applied quantitative 3-point Dixon and semiquantitative T1-weighted and short tau inversion recovery (STIR) imaging to bulbar and lower limb muscles and performed clinical and functional assessments in ALS (n = 21) and SBMA (n = 21), alongside healthy controls (n = 16). Acquired images were analyzed for the presence of fat infiltration or edema as well as specific patterns of muscle involvement. Quantitative MRI measurements were correlated with clinical measures of disease severity in ALS and SBMA.ResultsQuantitative imaging revealed significant fat infiltration in bulbar (p < 0.001) and limb muscles in SBMA compared to controls (thigh: p < 0.001; calf: p = 0.001), identifying a characteristic pattern of muscle involvement. In ALS, semiquantitative STIR imaging detected marked hyperintensities in lower limb muscles, distinguishing ALS from SBMA and controls. Finally, MRI measurements correlated significantly with clinical scales of disease severity in both ALS and SBMA.ConclusionsOur findings show that muscle MRI differentiates between SBMA and ALS and correlates with disease severity, supporting its use as a diagnostic tool and biomarker for disease progression. This highlights the clinical utility of muscle MRI in motor neuron disorders and contributes to establish objective outcome measures, which is crucial for the development of new drugs.