Date Published: April 5, 2019
Publisher: Public Library of Science
Author(s): Liang Qi, Lei Xu, Wen-Tao Wang, Yu-Dong Zhang, Rui Zhang, Yue-Fen Zou, Hai-Bin Shi, Xi Chen.
To investigate the value of dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) for evaluating denervated skeletal muscle in rabbits.
24 male rabbits were randomly divided into an irreversible neurotmesis group and a control group. In the experimental group, the sciatic nerves of rabbits were transected for irreversible neurotmesis model. A sham operation was performed in the control group. MRI of rabbit lower legs was performed before nerve surgery and 1 day, 3 days, 5 days, 1 week, 2 weeks, 3 weeks, 4 weeks, 6 weeks, 8 weeks, 10 weeks, and 12 weeks after surgery.
Signal intensity changes were seen in the left gastrocnemius muscle on the T2-weighted images. DCE-MRI derived parameters (Ktrans, Kep, and Vp) were measured in vivo. In the irreversible neurotmesis group, T2-weighted images showed increased signal intensity in the left gastrocnemius muscle. Ktrans, Vp values changes occur as early as 1 day after denervation, and increased gradually until 4 weeks after surgery. There are significant increases in both Ktrans and Vp values compared with those in the control group after surgery (P < 0.05). Kep values show no significant difference between the irreversible neurotmesis group and the control group. DCE-MRI hold the promise of an early and sensitive diagnosis of denervated skeletal muscle.
Peripheral nerve injury leads to morphologic and metabolic changes in the target denervated skeletal muscles. Electromyography (EMG) is useful for the diagnosis of denervated muscles . However, EMG sometimes presents some difficulties in the detection of denervated skeletal muscle because it is both invasive and dependent on the skill of the examiner, and it is difficult to obtain information that is useful, objective, and reproducible with EMG in the deep muscles or small intramuscular areas.
As in other studies, we demonstrate here that denervated skeletal muscle in the acute and subacute phase characteristically show high signal intensity on T2-weighted MR images [5, 6, 9]. However, to our knowledge, few studies available to date have used DCE MR imaging to evaluate denervated skeletal muscle. In this study, we evaluated the utility of DCE MR imaging for assessing denervated skeletal muscles in rabbits. Among the three different DCE MR imaging-derived parameters (Ktrans, Kep, and Vp values) used in this study, we found that compared to the uninjured nerves group (group A) showed a significant increase in Ktrans and Vp values of denervated skeletal muscle after surgery.
In summary, Ktrans and Vp values obtained from DCE MR imaging parameters changes occur as early as 1 day after denervation. Increased Ktrans and Vp values is an early phenomenon markedly preceding not only EMG abnormalities but also signal intensity changes after nerve transection. DCE MR imaging hold the promise of an early and sensitive diagnosis of denervated skeletal muscle.