Loss of electrical anisotropy is an unrecognized feature of dystrophic muscle that may serve as a convenient index of disease status.
OBJECTIVE
We sought to understand the alteration in the anisotropic, or direction dependent, character of muscle as measured by electrical impedance myography (EIM) in subjects with Duchenne muscular dystrophy (DMD) and its potential to serve as a biomarker of disease status.


METHODS
Thirty-six boys with DMD and 27 healthy controls were measured with EIM, with electrical current applied both parallel and perpendicular to the major muscle fiber direction. In addition, muscle extracted from 10 mdx and 10 wild-type mice were measured analogously.


RESULTS
Normalized reactance anisotropy, a direction-dependent measure of membrane charge storage capability, was significantly lower in the four muscles of DMD subjects as compared to controls (p<0.01). Normalized reactance anisotropy also decreased with increasing age in DMD subjects (r=-0.36, p=0.031), but not in healthy boys. Analogous changes were observed in mdx mouse gastrocnemius as compared to wild type (p=0.019).


CONCLUSIONS
These results support that loss of electrical anisotropy is a previously unrecognized feature of dystrophic muscle.


CONCLUSIONS
Anisotropic alterations may offer novel indices to assist in neuromuscular disease diagnosis and to serve as easy-to-obtain biomarkers in clinical therapeutic trials.
Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Ave, Boston, MA 02215, USA. Electronic address: srutkove@bidmc.harvard.edu.
Seward B
SB
Rutkove
Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Ave, Boston, MA 02215, USA.
Jim S
JS
Wu
Department of Neurology, Washington University in St. Louis, 660 S Euclid Ave, St. Louis, MO 63110, USA.
Craig
C
Zaidman
Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA.
Kush
K
Kapur
Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Ave, Boston, MA 02215, USA.
Sung
S
Yim
Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA.
Amy
A
Pasternak
Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA.
Lavanya
L
Madabusi
Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA.
Heather
H
Szelag
Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA.
Tim
T
Harrington
Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Ave, Boston, MA 02215, USA.
Jia
J
Li
Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Ave, Boston, MA 02215, USA.
Adam
A
Pacheck
Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA.
Basil T
BT
Darras
D000293:Adolescent; D000818:Animals; D016880:Anisotropy; D002648:Child; D002675:Child, Preschool; D018450:Disease Progression; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx; D018482:Muscle, Skeletal / Q000503:physiopathology*; D020388:Muscular Dystrophy, Duchenne / Q000175:diagnosis* / Q000235:genetics / Q000503:physiopathology*
Anisotropy; Biomarker; Duchenne muscular dystrophy; Impedance