P16 Measurement of intramuscular fat in the medial gastrocnemius of stroke patients
D’Souza A[1, 2], Bolsterlee B[1, 2] and Herbert R[1, 2]
- Neuroscience Research Australia, Randwick, NSW, Australia
- University of New South Wales, Randwick, NSW, Australia
The force producing capacity of a muscle depends on the cross-sectional area of the muscle fibers. Infiltration of intramuscular fat (IMF) reduces the cross-sectional area of muscle fibers per unit cross-sectional area of muscle, compromising the force producing capacity and, potentially changing muscle stiffness. Previous studies have shown that in stroke patients the muscles of the paretic side have increased IMF [1, 2]. We investigated IMF in the medial gastrocnemius of stroke patients.
MRI scans were used to quantify IMF of seven patients who have had a stroke (mean age 63±8 years) and 17 controls (mean age 69±10 years). Both legs were scanned in a 3T MRI scanner (Philips Achieva TX) using an mDixon protocol, from which reliable measurements of fat content were obtained. For stroke patients, IMF measurements were made of the muscle on the paretic and non-paretic sides. For control subjects, the mean IMF of the left and right muscle was used.
Linear mixed models compared (1) the paretic and non-paretic legs in stroke patients, and (2) the paretic leg of stroke patients and the control subjects.
This is the first report of IMF measurements using mDixon imaging in stroke patients. The mean difference between the paretic and non-paretic side was 2.7% (95%CI -1.5% – 6.9%), which was not significant. The paretic side showed 11% (7.6% – 15%) higher IMF than the control subjects.
These findings may help explain the increased stiffness often seen in the muscles of stroke patients.
- Ryan, A.S., et al., Hemiparetic muscle atrophy and increased intramuscular fat in stroke patients. Archives of Physical Medicine and Rehabilitation, 2002. 83(12): p. 1703-1707.
- Ramsay, J.W., et al., Paretic Muscle Atrophy and Non-Contractile Tissue Content in Individual Muscles of the Post-Stroke Lower Extremity. Journal of biomechanics, 2011. 44(16): p. 2741-2746.