phosphocreatine and Myasthenia-Gravis

To assess lipid composition of the intrinsic tongue muscles in patients with myasthenia gravis (MG).. This study included 15 MG patients with antibodies against muscle-specific kinase (MuSK), 15 matched MG patients with antibodies against acetylcholine receptor (AChR) and 15 matched healthy subjects. Middle posterior region of the tongue was analyzed by single voxel point-resolved proton magnetic resonance spectroscopy (MRS) using 1.5T MRI scanner.. MRS obtained from subject with AChR MG showed a broad resonance arising from methylene groups of lipids (PMN) with no observable shoulder attributed to methyl groups (PML). Full-width at half maximum (FWHM) of PMN+PML peak showed higher value in patients with AChR MG in comparison to healthy subjects and MuSK MG patients (p<0.05). In patients with MuSK MG, the shape and FWHM of PMN+PML peak was similar as in healthy subjects (p>0.05), with tendency toward increased ratio between PMN and resonance from vinyl protons of lipids (PV). In both AChR and MuSK MG, total creatine resonance (creatine+phosphocreatine, CP) was almost absent with significant increase of PMN/CP ratio in comparison to healthy subjects (p<0.05).. MRS is useful in revealing muscle lipid composition in MG. In patients with AChR MG, MRS showed increased lipid content in the tongue muscles due to the lipid migration from intra- to extramyocellular space. Finding in patients with MuSK MG might reflect intramyocellular lipid deposition in the tongue. CP decrease in tongue muscles indicated impairment of oxidative metabolism in both AChR MG and MuSK MG.

Topics: Adult; Autoantibodies; Body Mass Index; Creatine; Female; Humans; Lipids; Magnetic Resonance Imaging; Male; Middle Aged; Muscle, Skeletal; Myasthenia Gravis; Phosphocreatine; Protein-Tyrosine Kinases; Receptors, Cholinergic; Tongue

To prospectively assess muscle metabolism in myasthenia gravis (MG) patients before and after thymectomy by using phosphorus 31 (31P) magnetic resonance (MR) spectroscopy.. With institutional review board approval and informed consent, resting and dynamic (31)P MR spectroscopy were performed in 14 healthy volunteers (five men, nine women; mean age, 33 years; range, 23-48 years) and 16 MG patients (six men, 10 women; mean age, 37 years; range 18-50 years) before and after thymectomy. Patients were stratified into groups according to the modified Osserman classification: mild-MG group (classes I-IIA) and moderate-to-severe-MG group (classes IIB-IV). Variables compared among the three groups (Kruskal-Wallis test) included the inorganic phosphate (P(i))-adenosine triphosphate (ATP) (P(i)/ATP) ratio, phosphocreatine (PCr)-ATP (PCr/ATP) ratio, P(i)/PCr ratio, muscle pH at resting and at end-exercise ( 31)P MR spectroscopy, rate constant for PCr recovery (k(PCr)), and maximum oxidative capacity (V(max)). These variables were also compared in MG patients before and after thymectomy (Wilcoxon signed rank test).. There were no significant differences in resting P(i)/ATP, PCr/ATP, and P(i)/PCr ratios and resting muscle pH among the three groups (control group, 14; mild-MG group, nine; moderate-to-severe-MG group, seven). Comparison of the control group with the mild-MG group and comparison of the mild-MG group before thymectomy with the mild-MG group after thymectomy showed no significant differences in end-exercise P(i)/ATP, PCr/ATP, and P(i)/PCr ratios; end-exercise muscle pH; k(PCr); and V(max). Compared with the control and mild-MG groups, the moderate-to-severe-MG group had significantly higher end-exercise P(i)/ATP and P(i)/PCr ratios and significantly lower end-exercise muscle pH, k(PCr), and V(max) before thymectomy (P < or = .001), but these values showed significant restoration to normal after thymectomy (P = .018).. Mild-MG group patients have muscle oxidative metabolism similar to that of healthy control subjects, whereas moderate-to-severe-MG group patients have impaired V(max) during exercise and a noticeable shift to glycolytic metabolism, but these abnormalities are reversible after thymectomy.

Topics: Adenosine Triphosphate; Adolescent; Adult; Female; Humans; Isotonic Contraction; Magnetic Resonance Spectroscopy; Male; Middle Aged; Muscle, Skeletal; Myasthenia Gravis; Phosphates; Phosphocreatine; Thymectomy

Topics: Adenosine Triphosphate; Humans; Magnetic Resonance Spectroscopy; Muscle, Skeletal; Myasthenia Gravis; Phosphates; Phosphocreatine; Thymectomy

Topics: Biochemical Phenomena; Coenzymes; Humans; Myasthenia Gravis; Phosphocreatine