Magnetic Resonance Imaging of the Skeletal Musculature by Marc-André Weber

Author:Marc-André Weber
Language: eng
Format: epub
Publisher: Springer Berlin Heidelberg, Berlin, Heidelberg

4.3 Glycogen Storage Diseases

Glycogenoses (Vorgerd et al. 2002a) in general, and McArdle’s disease in particular (glycogenosis type V), have been in the interest of MRS since the very beginning, on the one hand because it was one of the first observations (Ross et al. 1981) of the value of 31P-MRS, and on the other hand because the pH development during exercise is pathognomonic in McArdle’s disease. For a systematic review of glycogenoses, clinical reviews are available (Vorgerd and Zange 2002; Vorgerd et al. 2002a). In the following, glycogenoses are listed not systematically but according to the role that MR spectroscopy has played in the past.

McArdle’s disease (glycogenosis type V) is an autosomal recessive inherited defect of the muscle glycogen phosphorylase which leads to a reduced ability to use glycogen reserves when energy is needed. In a seminal paper, Ross et al. (1981) have shown the potential of 31P-MRS to follow the pH development during exercise which—in contrast to healthy subjects—becomes alkaline in McArdle patients. In addition, PCr depletion and Pi increase during exercise is much more pronounced in these patients. Figure 8 illustrates that a reduced breakdown of glycogen is responsible for the fact that glycogen reserves cannot be used during exercise in the same amount as in healthy subjects (Argov et al. 1987). In turn, it has been shown that glucose infusion leads to an improvement in the clinical symptoms and the PCr reduction (Lewis et al. 1985), since glucose gets available via glucose transport to the cell instead of the impaired glycogenolysis. In a family with multiple consanguinities and parents with overt McArdle’s disease, 31P-MRS has shown the pathognomonic pH-behavior in a so far totally asymptomatic 5-year-old boy (Gruetter et al. 1990). In a comparison of 31P-MRS data and T2-MRI-measurements, McArdle patients neither showed a pH drop nor changes of T2 as seen in healthy controls (deKerviler et al. 1991). Using 13C-MR spectroscopy, it was possible to directly observe the glycogen reserves in skeletal muscle and thus to distinguish McArdle patients with increased glycogen levels from healthy controls (Jehenson et al. 1991). Figure 8 also shows this potential of observing the metabolism in vivo at different places of the biochemical pathways using MRS of different nuclei. In a patient suffering from glycogenosis type VI (liver glycogen phosphorylase deficiency), where muscle is not involved, normal glycogen levels were found in skeletal muscle, yet increased glycogen levels were observed in liver, thus allowing a differentiation from McArdle glycogenosis where skeletal muscle is affected (Labrune et al. 1992). Different phases of the exercise-related changes in 31P-MR signals in McArdle patients were reported in more detail, such as the transient Pi disappearance at the onset of recovery (Bendahan et al. 1992a), the failure to show cytosolic acidification and PME accumulation (Siciliano et al. 1995), the indirectly observed ADP (Argov et al. 1996), or functional compartmentation with a small number of muscle fibers that reach metabolic depletion earlier than the majority (Zange et al. 2003). 31P-MR spectroscopy was also used to follow and

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