Use of magnetic resonance imaging and P-31 magnetic resonance spectroscopy to detect and quantify muscle dysfunction in the amyopathic and myopathic variants of dermatomyositis.
OBJECTIVE
To investigate the use of magnetic resonance imaging (MRI) and P-31 magnetic resonance spectroscopy (MRS) in characterizing the metabolic and functional status of muscles in patients with amyopathic dermatomyositis (DM) and to compare the findings with those in patients with classic myopathic DM.


METHODS
Nine patients with amyopathic DM, 11 patients with myopathic DM, and 11 normal individuals were studied. MRI images of thigh muscles were obtained, and T1 and T2 relaxation times were calculated. Biochemical status was quantitated with P-31 MRS, by determining concentrations of phosphate metabolites during rest and exercise.


RESULTS
Patients with amyopathic DM showed no muscle inflammation, and MRS data obtained during rest were normal. During exercise at 25% and 50% maximum voluntary contractile force, the MRS data revealed significant differences between amyopathic DM patients and control subjects indicating inefficient metabolism. In contrast, muscles of patients with myopathic DM showed inflammation and metabolic abnormalities even during rest.


CONCLUSIONS
Metabolic deficiencies in patients with amyopathic DM were unmasked by exercise, suggesting that the 2 DM syndromes may share muscle abnormalities. MRI/MRS may be useful in diagnosis and optimization of treatment.
Park
J H
JH
Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232.
Olsen
N J
NJ
King
L
L
Vital
T
T
Buse
R
R
Kari
S
S
Hernanz-Schulman
M
M
Price
R R
RR
D000328:Adult; D000368:Aged; D003882:Dermatomyositis / Q000175:diagnosis* / Q000503:physiopathology; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D009132:Muscles / Q000378:metabolism* / Q000503:physiopathology; D009135:Muscular Diseases / Q000175:diagnosis* / Q000503:physiopathology*; D010710:Phosphates / Q000032:analysis; D010725:Phosphocreatine / Q000032:analysis; D010759:Phosphorus Isotopes; D012146:Rest / Q000502:physiology; D012871:Skin Diseases / Q000175:diagnosis* / Q000503:physiopathology*; D014938:Work Capacity Evaluation
D010710:Phosphates; D010759:Phosphorus Isotopes; D010725:Phosphocreatine