Denervated human skeletal muscle: MR imaging evaluation.

Abstract

Because determination of neurologic integrity after severe limb trauma is crucial in patient care, the authors assessed magnetic resonance (MR) imaging as a tool to map denervated motor units of skeletal muscle in patients with traumatic peripheral neuropathy. Denervation was confirmed in 22 patients with use of electromyography, surgery, or both. MR imaging was performed with moderately T1- and T2-weighted spin-echo and short-tau inversion-recovery (STIR) sequences. MR imaging was unreliable in depicting acute denervation. Muscles of patients with subacute denervation had prolonged T1 and T2, which contributed to conspicuous hyperintensity on STIR images. Chronically denervated muscles showed marked atrophy, variable changes on STIR images, and conspicuous fatty infiltration on T1-weighted images. Normal variants in motor unit anatomy were seen in denervated muscle volumes outside the expected distribution of the injured nerve. MR imaging is promising for the noninvasive mapping and monitoring of denervated muscle in subacute and chronic phases of peripheral neuropathy.

Line scan diffusion spectrum of the denervated rat skeletal muscle

“…MRI can detect the change of muscle objectively and distinguish denervation from tendon rupture or malingering (13). Characteristic changes in MR signal intensity of denervated skeletal muscle are high signal intensity on T2-weighted MR images with normal intensity on T1-weighted MR images (13)(14)(15)(16)(17)(18). This phenomenon is considered to reflect the increase of extracellular space and water content (13).…”

“…This phenomenon is considered to reflect the increase of extracellular space and water content (13). It takes two to eight weeks after the onset to detect the high signal intensity of denervated skeletal muscle on T2-weighted MR images (13,(15)(16)(17)(18), though Bendszus and Koltzenburg (14) mentioned that they could detect the change of signal intensity as early as 24 hours after the transection of the rat sciatic nerve with T1-weighted Gd-enhanced MRI. In the present study, it took approximately seven days to distin- Figure 4.…”

“…An increase of extracellular fluid space resulted in changes in signal intensity of denervated skeletal muscle on T2-weighted MR images (13). It typically took up to seven days before this change became visible (13,(15)(16)(17)(18).…”

Role of Skeletal Muscle MRI inPeripheral Nerve Disorders

“…The lesion sites may be inferred based on the distribution of the involved muscles. After the first report in 1987 (Shabas et al, 1987), MRI has increasingly been used to evaluate denervated muscles (West et al, 1994;Fleckenstein et al, 1993;Uetani et al, 1993). In particular, studies of entrapment or compressive neuropathy have greatly contributed to the understanding of clinical-radiological correlations in peripheral nerve damage.…”

A 48-year-old man with chronic right shoulder pain and weakness after a fall: diagnosis and discussion

“…However, EMG is painful and operatordependent. MR imaging, on the other hand, is a noninvasive technique that can help provide a diagnosis, especially when other diagnoses besides axillary nerve injury are being considered [3].…”