[Exploration of exercise intolerance by 31P NMR spectroscopy of calf muscles coupled with MRI and ergometry].
One hundred patients presenting with exercise intolerance or rhabdomyolysis episodes have been examined successively by 31P Nuclear Magnetic Resonance Spectroscopy (MRS) of leg plantar flexor muscles with exercise test. In all cases a muscle biopsy was performed. At the end of investigations, diagnosis of a metabolic myopathy was made in 33 patients: glycogenolysis or glycolysis deficiency in 8 cases, mitochondrial myopathy in 24 cases and CPT II deficiency in one case. Muscular dystrophy or congenital myopathy were diagnosed in 6 cases. No precise etiology could be found in 30 patients with either high CK levels or muscle biopsy abnormalities. Seven patients had rhabdomyolysis related to excessive physical activities. Twenty-four patients had functional symptoms. The principal MRS parameters used for diagnosis were the values of intracellular pH at the end of exercise and the time constant of phosphocreatine resynthesis during recovery. Lack of acidosis after exercise was observed in all patients with blockade of glycogenolysis or glycolysis. A slowing in phosphocreatine resynthesis was found in 66 p.cent of patients with definite mitochondrial myopathy. The specificity of these parameters were respectively 92.4 p.cent and 85.5 p.cent for the two groups. In conclusion (31)P MRS allows the detection of muscular glycogenoses with a sensitivity close to 100 p.cent. However, its sensitivity was lower for the detection of mitochondrial myopathies, as is also known for the other in vivo metabolic investigations, reflecting the heterogeneity of expression of mitochondrial abnormalities in a given muscle. The integration of imaging in the examination protocol may help to orientate towards the diagnostic of a dystrophy in some patients.
Laforêt
P
P
Institut de Myologie, Fédération de Neurologie Mazarin, Hôpital de la Salpêtrière, Paris.
Wary
C
C
Duteil
S
S
de Kerviler
E
E
Carlier
P G
PG
Lombès
A
A
Romero
N B
NB
Fardeau
M
M
Eymard
B
B
Leroy-Willig
A
A
D000293:Adolescent; D000328:Adult; D000368:Aged; D015444:Exercise; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006003:Glycogen / Q000378:metabolism; D006019:Glycolysis; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000201:enzymology / Q000473:pathology* / Q000503:physiopathology; D010725:Phosphocreatine / Q000378:metabolism; D012206:Rhabdomyolysis / Q000201:enzymology / Q000473:pathology* / Q000503:physiopathology
D010725:Phosphocreatine; D006003:Glycogen