Arne Fischmann

MRI biomarker assessment of neuromuscular disease progression: a prospective observational cohort study

Summary Background A substantial impediment to progress in trials of new therapies in neuromuscular disorders is the absence of responsive outcome measures that correlate with patient functional deficits and are sensitive to early disease processes. Irrespective of the primary molecular defect, neuromuscular disorder pathological processes include disturbance of intramuscular water distribution followed by intramuscular fat accumulation, both quantifiable by MRI. In pathologically distinct neuromuscular disorders, we aimed to determine the comparative responsiveness of MRI outcome measures over 1 year, the validity of MRI outcome measures by cross-sectional correlation against functionally relevant clinical measures, and the sensitivity of specific MRI indices to early muscle water changes before intramuscular fat accumulation beyond the healthy control range. Methods We did a prospective observational cohort study of patients with either Charcot-Marie-Tooth disease 1A or inclusion body myositis who were attending the inherited neuropathy or muscle clinics at the Medical Research Council (MRC) Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, London, UK. Genetic confirmation of the chromosome 17p11·2 duplication was required for Charcot-Marie-Tooth disease 1A, and classification as pathologically or clinically definite by MRC criteria was required for inclusion body myositis. Exclusion criteria were concomitant diseases and safety-related MRI contraindications. Healthy age-matched and sex-matched controls were also recruited. Assessments were done at baseline and 1 year. The MRI outcomes—fat fraction, transverse relaxation time (T2), and magnetisation transfer ratio (MTR)—were analysed during the 12-month follow-up, by measuring correlation with functionally relevant clinical measures, and for T2 and MTR, sensitivity in muscles with fat fraction less than the 95th percentile of the control group. Findings Between Jan 19, 2010, and July 7, 2011, we recruited 20 patients with Charcot-Marie-Tooth disease 1A, 20 patients with inclusion body myositis, and 29 healthy controls (allocated to one or both of the 20-participant matched-control subgroups). Whole muscle fat fraction increased significantly during the 12-month follow-up at calf level (mean absolute change 1·2%, 95% CI 0·5–1·9, p=0·002) but not thigh level (0·2%, −0·2 to 0·6, p=0·38) in patients with Charcot-Marie-Tooth disease 1A, and at calf level (2·6%, 1·3–4·0, p=0·002) and thigh level (3·3%, 1·8–4·9, p=0·0007) in patients with inclusion body myositis. Fat fraction correlated with the lower limb components of the inclusion body myositis functional rating score (ρ=–0·64, p=0·002) and the Charcot-Marie-Tooth examination score (ρ=0·63, p=0·003). Longitudinal T2 and MTR changed consistently with fat fraction but more variably. In muscles with a fat fraction lower than the control group 95th percentile, T2 was increased in patients compared with controls (regression coefficients: inclusion body myositis thigh 4·0 ms [SE 0·5], calf 3·5 ms [0·6]; Charcot-Marie-Tooth 1A thigh 1·0 ms [0·3], calf 2·0 ms [0·3]) and MTR reduced compared with controls (inclusion body myositis thigh −1·5 percentage units [pu; 0·2], calf −1·1 pu [0·2]; Charcot-Marie-Tooth 1A thigh −0·3 pu [0·1], calf −0·7 pu [0·1]). Interpretation MRI outcome measures can monitor intramuscular fat accumulation with high responsiveness, show validity by correlation with conventional functional measures, and detect muscle water changes preceding marked intramuscular fat accumulation. Confirmation of our results in further cohorts with these and other muscle-wasting disorders would suggest that MRI biomarkers might prove valuable in experimental trials. Funding Medical Research Council UK.

Quantification of fat infiltration in oculopharyngeal muscular dystrophy: Comparison of three MR imaging methods

To analyze and compare three quantitative MRI methods to determine the degree of muscle involvement in oculopharyngeal muscular dystrophy (OPMD).

Quantitative muscle MRI: A powerful surrogate outcome measure in Duchenne muscular dystrophy

In muscular dystrophies quantitative muscle MRI (qMRI) detects disease progression more sensitively than clinical scores. This prospective one year observational study compared qMRI with clinical scores in Duchenne muscular dystrophy (DMD) to investigate if qMRI can serve as a surrogate outcome measure in clinical trials. In 20 DMD patients the motor function measure (MFM) total and subscores (D1-D3) were done for physical examination, and the fat fraction (MFF) of thigh muscle qMRI was obtained using the two-point Dixon method. Effect sizes (ES) were calculated for all measures. Sample size estimation (SS) was done modelling assumed treatment effects. Ambulant patients <7 years at inclusion improved in the MFM total and D1 score (ES 1.1 and 1.0). Ambulant patients >7 years (highest ES in the MFM D1 subscore (1.2)), and non-ambulant patients (highest ES in the total MFM score (0.7)) worsened. In comparison the ES of QMRI was much larger, e.g. SS estimations for qMRI data were up to 17 fold smaller compared to the MFM total score and up to 7 fold to the D1 subscore, respectively. QMRI shows pathophysiological changes in DMD and might serve as a surrogate outcome measure in clinical trials.

Muscle MRI reveals distinct abnormalities in genetically proven non-dystrophic myotonias

We assessed the presence, frequency and pattern of MRI abnormalities in non-dystrophic myotonia patients. We reviewed T1-weighted and STIR (short-tau-inversion-recovery) 3T MRI sequences of lower limb muscles at thigh and calf level in 21 patients with genetically confirmed non-dystrophic myotonia: 11 with CLCN1 mutations and 10 with SCN4A mutations, and 19 healthy volunteers. The MRI examinations of all patients showed hyperintensity within muscles on either T1-weighted or STIR images. Mild extensive or marked T1-weighted changes were noted in 10/21 patients and no volunteers. Muscles in the thigh were equally likely to be affected but in the calf there was sparing of tibialis posterior. Oedema was common in calf musculature especially in the medial gastrocnemius with STIR hyperintensity observed in 18/21 patients. In 10/11 CLCN1 patients this included a previously unreported “central stripe”, also present in 3/10 SCN4A patients but no volunteers. Degree of fatty infiltration correlated with age (rho = 0.46, p < 0.05). Muscle MRI is frequently abnormal in non-dystrophic myotonia providing evidence of fatty infiltration and/or oedema. The pattern is distinct from other myotonic disorders; in particular the “central stripe” has not been reported in other conditions. Correlations with clinical parameters suggest a potential role for MRI as a biomarker.

Improved Muscle Function in Duchenne Muscular Dystrophy through L-Arginine and Metformin: An Investigator-Initiated, Open-Label, Single-Center, Proof-Of-Concept-Study

Altered neuronal nitric oxide synthase function in Duchenne muscular dystrophy leads to impaired mitochondrial function which is thought to be one cause of muscle damage in this disease. The study tested if increased intramuscular nitric oxide concentration can improve mitochondrial energy metabolism in Duchenne muscular dystrophy using a novel therapeutic approach through the combination of L-arginine with metformin. Five ambulatory, genetically confirmed Duchenne muscular dystrophy patients aged between 7–10 years were treated with L-arginine (3 x 2.5 g/d) and metformin (2 x 250 mg/d) for 16 weeks. Treatment effects were assessed using mitochondrial protein expression analysis in muscular biopsies, indirect calorimetry, Dual-Energy X-Ray Absorptiometry, quantitative thigh muscle MRI, and clinical scores of muscle performance. There were no serious side effects and no patient dropped out. Muscle biopsy results showed pre-treatment a significantly reduced mitochondrial protein expression and increased oxidative stress in Duchenne muscular dystrophy patients compared to controls. Post-treatment a significant elevation of proteins of the mitochondrial electron transport chain was observed as well as a reduction in oxidative stress. Treatment also decreased resting energy expenditure rates and energy substrate use shifted from carbohydrates to fatty acids. These changes were associated with improved clinical scores. In conclusion pharmacological stimulation of the nitric oxide pathway leads to improved mitochondria function and clinically a slowing of disease progression in Duchenne muscular dystrophy. This study shall lead to further development of this novel therapeutic approach into a real alternative for Duchenne muscular dystrophy patients. Trial Registration ClinicalTrials.gov NCT02516085

The regeneration potential after human and autologous stem cell transplantation in a rat sciatic nerve injury model can be monitored by MRI.

Traumatic nerve injuries are a major clinical challenge. Tissue engineering using a combination of nerve conduits and cell-based therapies represents a promising approach to nerve repair. The aim of this study was to examine the regeneration potential of human adipose-derived stem cells (hASCs) after transplantation in a nonautogenous setting and to compare them with autogenous rat ASCs (rASCs) for early peripheral nerve regeneration. Furthermore, the use of MRI to assess the continuous process of nerve regeneration was elaborated. The sciatic nerve injury model in female Sprague-Dawley rats was applied, and a 10-mm gap created by using a fibrin conduit seeded with the following cell types: rASCs, Schwann cell (SC)-like cells from rASC, rat SCs (rSCs), hASCs from the superficial and deep abdominal layer, as well as human stromal vascular fraction (1 × 106 cells). As a negative control group, culture medium only was used. After 2 weeks, nerve regeneration was assessed by immunocytochemistry. Furthermore, MRI was performed after 2 and 4 weeks to monitor nerve regeneration. Autogenous ASCs and SC-like cells led to accelerated peripheral nerve regeneration, whereas the human stem cell groups displayed inferior results. Nevertheless, positive tends could be observed for hASCs from the deep abdominal layer. By using a clinical 3T MRI scanner, we were able to visualize the graft as a small black outline and small hyperintensity indicating the regenerating axon front. Furthermore, a strong correlation was found between the length of the regenerating axon front measured by MRI and the length measured by immunocytochemistry (r = 0.74, p = 0.09). We successfully transplanted and compared human and autologous stem cells for peripheral nerve regeneration in a rat sciatic nerve injury model. Furthermore, we were able to implement the clinical 3T MRI scanner to monitor the efficacy of cellular therapy over time.

Improved Anatomical Reproducibility in Quantitative Lower-Limb Muscle MRI

To compare the influence of two limb positions and slice prescription using scout‐image–based and surface‐anatomy–based methods on the reproducibility of quantitative MRI of lower‐limb muscles.

Peripheral Nerve Repair: Multimodal Comparison of the Long-Term Regenerative Potential of Adipose Tissue-Derived Cells in a Biodegradable Conduit

Tissue engineering is a popular topic in peripheral nerve repair. Combining a nerve conduit with supporting adipose-derived cells could offer an opportunity to prevent time-consuming Schwann cell culture or the use of an autograft with its donor site morbidity and eventually improve clinical outcome. The aim of this study was to provide a broad overview over promising transplantable cells under equal experimental conditions over a long-term period. A 10-mm gap in the sciatic nerve of female Sprague-Dawley rats (7 groups of 7 animals, 8 weeks old) was bridged through a biodegradable fibrin conduit filled with rat adipose-derived stem cells (rASCs), differentiated rASCs (drASCs), human (h)ASCs from the superficial and deep abdominal layer, human stromal vascular fraction (SVF), or rat Schwann cells, respectively. As a control, we resutured a nerve segment as an autograft. Long-term evaluation was carried out after 12 weeks comprising walking track, morphometric, and MRI analyses. The sciatic functional index was calculated. Cross sections of the nerve, proximal, distal, and in between the two sutures, were analyzed for re-/myelination and axon count. Gastrocnemius muscle weights were compared. MRI proved biodegradation of the conduit. Differentiated rat ASCs performed significantly better than undifferentiated rASCs with less muscle atrophy and superior functional results. Superficial hASCs supported regeneration better than deep hASCs, in line with published in vitro data. The best regeneration potential was achieved by the drASC group when compared with other adipose tissue-derived cells. Considering the ease of procedure from harvesting to transplanting, we conclude that comparison of promising cells for nerve regeneration revealed that particularly differentiated ASCs could be a clinically translatable route toward new methods to enhance peripheral nerve repair.

Skeletal muscle MRI of the lower limbs in congenital muscular dystrophy patients with novel POMT1 and POMT2 mutations

Alpha-dystroglycanopathies form a genetically heterogeneous group of congenital muscular dystrophies with a large variety of clinical phenotypes. Within this group mutations in the protein O-mannosyltransferase genes (POMT1 and POMT2) are known to cause a spectrum of CMD disorders including the Walker-Warburg Syndrome with severe brain and ocular malformations, and the limb girdle muscular dystrophy with and without mental retardation. In this case report the clinical phenotype and brain and muscle MRI findings of two siblings of 10 and 7years (male/female) homozygous for a novel mutation in the POMT1 gene (c.2220G>C, p.Trp740Cys) and a 10year old boy with two novel mutations in the POMT2 gene ((c.215G>A, p.Arg72His) and (c.713G>T, p.Gly238Val) are presented. Mutation detection was performed by direct sequencing of the FKRP, FKTN, POMT1 and POMT2 genes. T1-weighted axial muscle MRI of the lower limbs revealed diffuse fatty degeneration of thigh and calf muscles with predominance of gluteus maximus, adductor magnus, posterior thigh, medial gastrocnemius, and peroneus muscles, but no edematous changes. As a similar pattern of muscle involvement had been described in FKRP related α-dystroglycanopathy LGMD2I, we conclude that α-dystroglycanopathies may present with distinctive muscle MRI changes.

Longitudinal 2-point dixon muscle magnetic resonance imaging in becker muscular dystrophy.

Introduction: Quantitative MRI techniques detect disease progression in myopathies more sensitively than muscle function measures or conventional MRI. To date, only conventional MRI data using visual rating scales are available for measurement of disease progression in Becker muscular dystrophy (BMD). Methods: In 3 patients with BMD (mean age 36.8 years), the mean fat fraction (MFF) of the thigh muscles was assessed by MRI at baseline and at 1‐year follow‐up using a 2‐point Dixon approach (2PD). The motor function measurement scale (MFM) was used for clinical assessment. Results: The mean MFF of all muscles at baseline was 61.6% (SD 7.6). It increased by 3.7% to 65.3% (SD 4.7) at follow‐up. The severity of muscle involvement varied between various muscle groups. Conclusions: As in other myopathies, 2PD can quantify fatty muscle degeneration in BMD and can detect disease progression in a small sample size and at relatively short imaging intervals. Muscle Nerve 51: 918–921, 2015