title: Peripheral nerve injury: diagnosis with MR imaging of denervated skeletal muscle--experimental study in rats.
abstract: OBJECTIVE
  To prospectively evaluate signal intensity change on T2-weighted magnetic resonance (MR) images and the time course of T2 values and T2 ratios after reinnervation in various nerve injury models in rats.
  
  
  METHODS
  Institutional animal use and care committee approval was obtained. Thirty male rats made up four groups of rats with an injured left posterior tibial nerve (irreversible neurotmesis, reversible neurotmesis, severe axonotmesis, or moderate axonotmesis) and one control group. There were six rats in each group. Signal intensity changes were seen in the gastrocnemius muscle on the T2-weighted MR images. T2 values were also measured in vivo with the Carr-Purcell-Meiboom-Gill method. Gait function was assessed by calculating the print length factor (PLF). T2 ratios and PLFs on the injured side were compared with those on the unaffected side. Ratios of specific acquisition points within groups were compared by using repeated-measures analysis of variance. Comparisons across the five groups at each acquisition point were performed by using one-way analysis of variance with Scheffe post hoc testing. P < .05 indicated a significant difference.
  
  
  RESULTS
  The more severe the nerve damage, the higher the signal intensity on T2-weighted MR images. There were significant differences in T2 ratios between the nerve injury groups and the control group (P < .05). Changes in T2 values and ratios depended on the degree of nerve injury. In the reversible neurotmesis group, T2 values and ratios began to decrease 28 days after surgery. In the severe and moderate axonotmesis groups, T2 values and ratios began to decrease 14 days after surgery. The starting point of functional recovery also depended on the degree of nerve injury.
  
  
  CONCLUSIONS
  The degree and prognosis of nerve injury can be evaluated by observing changes in signal intensity on T2-weighted images and the time course of T2 values and ratios.
authors: Department of Orthopaedic Surgery, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
authors: Eiko
authors: E
authors: Yamabe
authors: Toshiyasu
authors: T
authors: Nakamura
authors: Koichi
authors: K
authors: Oshio
authors: Yoshito
authors: Y
authors: Kikuchi
authors: Hiroyasu
authors: H
authors: Ikegami
authors: Yoshiaki
authors: Y
authors: Toyama
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D004195:Disease Models, Animal; D004576:Electromyography; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009121:Muscle Denervation; D059348:Peripheral Nerve Injuries; D010525:Peripheral Nerves / Q000503:physiopathology; D010523:Peripheral Nervous System Diseases / Q000175:diagnosis* / Q000503:physiopathology; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D051381:Rats; D017208:Rats, Wistar