Corrigendum: Magnetization Transfer Ratio in Lower Limbs of Late Onset Pompe Patients Correlates With Intramuscular Fat Fraction and Muscle Function Tests.

[This corrects the article DOI: 10.3389/fneur.2021.634766.].

Magnetization Transfer Ratio in Lower Limbs of Late Onset Pompe Patients Correlates With Intramuscular Fat Fraction and Muscle Function Tests.

Objectives: Magnetization transfer (MT) imaging exploits the interaction between bulk water protons and protons contained in macromolecules to induce signal changes through a special radiofrequency pulse. MT detects muscle damage in patients with neuromuscular conditions, such as limb-girdle muscular dystrophies or Charcot-Marie-Tooth disease, which are characterized by progressive fiber loss and replacement by fatty tissue. In Pompe disease, in which there is, in addition, an accumulation of glycogen inside the muscle fibers, MT has not been tested yet. Our aim is to estimate MT ratio (MTR) in the skeletal muscle of these patients and correlate it with intramuscular fat fraction (FF) and results of muscle function tests. Methods: We obtained two-point axial Dixon and Dixon-MT sequences of the right thigh on a 1.5 Teslas MRI scanner in 60 individuals, including 29 late onset Pompe disease patients, 2 patients with McArdle disease, and 29 age and sex matched healthy controls. FF and MTR were estimated. Muscle function using several muscle function tests, including quantification of muscle strength, timed test quality of life scales, conventional spirometry obtaining forced vital capacity while sitting and in the supine position, were assessed in all patients. Results: MTR was significantly lower in Pompe patients compared with controls (45.5 ± 8.5 vs. 51.7 ± 2.3, Student T-test, p < 0.05). There was a negative correlation between the MTR and FF muscles studied (correlation coefficient: -0.65, Spearman test: p < 0.05). MTR correlated with most of the muscle function test results. We analyzed if there was any difference in MTR values between Pompe patients and healthy controls in those muscles that did not have an increase in fat, a measure that could be related to the presence of glycogen in skeletal muscles, but we did not identify significant differences except in the adductor magnus muscle (48.4 ± 3.6 in Pompe vs. 51 ± 1.3 in healthy controls, Student T-test = 0.023). Conclusions: MTR is a sensitive tool to identify muscle loss in patients with Pompe disease and shows a good correlation with muscle function tests. Therefore, the MT technique can be useful in monitoring muscle degeneration in Pompe disease in clinical trials or natural history studies.

Follow-up of late-onset Pompe disease patients with muscle magnetic resonance imaging reveals increase in fat replacement in skeletal muscles.

BACKGROUND: Late-onset Pompe disease (LOPD) is a genetic disorder characterized by progressive degeneration of the skeletal muscles produced by a deficiency of the enzyme acid alpha-glucosidase. Enzymatic replacement therapy with recombinant human alpha-glucosidase seems to reduce the progression of the disease; although at the moment, it is not completely clear to what extent. Quantitative muscle magnetic resonance imaging (qMRI) is a good biomarker for the follow-up of fat replacement in neuromuscular disorders. The aim of this study was to describe the changes observed in fat replacement in skeletal muscles using qMRI in a cohort of LOPD patients followed prospectively. METHODS: A total of 36 LOPD patients were seen once every year for 4 years. qMRI, several muscle function tests, spirometry, activities of daily living scales, and quality-of-life scales were performed on each visit. Muscle MRI consisted of two-point Dixon studies of the trunk and thigh muscles. Computer analysis of the images provided the percentage of muscle degenerated and replaced by fat in every muscle (known as fat fraction). Longitudinal analysis of the measures was performed using linear mixed models applying the Greenhouse-Geisser test. RESULTS: We detected a statistically significant and continuous increase in mean thigh fat fraction both in treated (+5.8% in 3 years) and in pre-symptomatic patients (+2.6% in 3years) (Greenhouse-Geisser p < 0.05). As an average, fat fraction increased by 1.9% per year in treated patients, compared with 0.8% in pre-symptomatic patients. Fat fraction significantly increased in every muscle of the thighs. We observed a significant correlation between changes observed in fat fraction in qMRI and changes observed in the results of the muscle function tests performed. Moreover, we identified that muscle performance and mean thigh fat fraction at baseline visit were independent parameters influencing fat fraction progression over 4 years (analysis of covariance, p < 0.05). CONCLUSIONS: Our study identifies that skeletal muscle fat fraction continues to increase in patients with LOPD despite the treatment with enzymatic replacement therapy. These results suggest that the process of muscle degeneration is not stopped by the treatment and could impact muscle function over the years. Hereby, we show that fat fraction along with muscle function tests can be considered a good outcome measures for clinical trials in LOPD patients.

Pancreatic duct after pancreatoduodenectomy: morphologic and functional evaluation with secretin-stimulated MR pancreatography.

OBJECTIVE: The purpose of this study was to evaluate the usefulness of secretin-enhanced MR pancreatography in evaluating morphologic changes and pancreatic function after pancreatoduodenectomy. SUBJECTS AND METHODS: Twenty patients who underwent pancreatoduodenectomy were evaluated with secretin MR pancreatography. Single-shot fast spin-echo T2-weighted dynamic MR pancreatograms were obtained before and every minute for 10 min after secretin injection. Image analysis included image quality for the visualization of the pancreatic duct and morphologic features of the pancreatic duct (side branches, ductal narrowing, irregular ductal contour, and patency of the anastomotic site). Pancreatic function was assessed using the Van de Kamer method and the fasting blood glucose and oral glucose tolerance tests. Jejunal filling was graded from the lowest amount of filling (grade 1) to normal filling (grade 3) on the last MR pancreatogram. RESULTS: The visualization of the main pancreatic duct was significantly improved with dynamic MR pancreatography (p < 0.05). The anastomotic site was visualized in 14 patients (70%) on MR pancreatography after secretin administration (p < 0.05). No statistically significant improvement in other morphologic data was seen after secretin administration. The sensitivity, specificity, positive predictive value, and negative predictive value of reduced jejunal filling (grade 1) for assessment of reduced pancreatic exocrine function were 92%, 71%, 85%, and 83%, respectively. The relation between reduced jejunal filling (grade 1) and diabetes was statistically significant (p < 0.05). CONCLUSION: The administration of secretin improves visualization of the pancreatic ducts and helps in the evaluation of remnant pancreatic function after pancreatoduodenectomy.

Doppler in hepatic cirrhosis and chronic hepatitis.

Doppler ultrasound and color Doppler are being used routinely in the study of vascular structures of the abdomen, and more particularly the liver. Reports published in the literature to date have shown that all patients with hepatic cirrhosis and chronic hepatitis should be studied in the first stage of their illness and in follow-up by using Doppler techniques. With new ultrasound software and the latest generation of contrast agents, we can obtain a better and more complete vascular study of the liver, which previously could be achieved only with triple-phase CT. Therefore, hepatic cirrhosis and chronic hepatitis, as well as their vascular complications, can be followed up more closely. The vascular complications include flow alterations in the hepatic artery and veins, portal hypertension, portal vein thrombosis, portosystemic shunts, and vascularization associated with liver tumors.