High-resolution magnetic resonance imaging is a noninvasive method of observing injury and recovery in the peripheral nervous system.
OBJECTIVE
Noninvasive observation of degenerating and regenerating peripheral nerves could improve the diagnosis and treatment of nerve injuries. We constructed a novel phased-array radiofrequency coil to permit magnetic resonance imaging (MRI) observation of the sciatic nerve and its target muscles in rats after injury.


METHODS
Adult male Lewis rats underwent either crushing (n = 18) or cutting and capping (n = 17) of their right sciatic nerves and then underwent serial MRI. Serial gait track analysis was performed to assess behavioral recovery. Animals from both groups were killed at several time points for histological evaluation of the nerves, with axon counting.


RESULTS
Crushed sciatic nerves demonstrated increased T2-weighted signals, followed by signal normalization as axonal regeneration and behavioral recovery occurred. Cut sciatic nerves prevented from regenerating displayed a prolonged phase of increased signal intensity. Acutely denervated muscles exhibited hyperintense T2-weighted signals, which normalized with reinnervation and behavioral recovery. Chronically denervated muscles demonstrated persistently increased T2-weighted signals and atrophy.


CONCLUSIONS
In this study, we demonstrated the ability of MRI to noninvasively monitor injury and recovery in the peripheral nervous system, by demonstrating changes in nerve and muscle that correlated with histological and behavioral evidence of axonal degeneration and regeneration. This study demonstrates the potential of MRI to distinguish traumatic peripheral nerve injuries that recover through axonal regeneration (i.e., axonotmetic grade) from those that do not and therefore require surgical repair (i.e., neurotmetic grade). This diagnostic modality could improve treatment by providing earlier and more accurate diagnoses of nerve damage, as well as reducing the need for exploratory surgery.
Aagaard
Beverly D
BD
Department of Radiology, University of Washington School of Medicine, Seattle, Washington 98195, USA.
Lazar
Daniel A
DA
Lankerovich
Luba
L
Andrus
Kathleen
K
Hayes
Cecil E
CE
Maravilla
Kenneth
K
Kliot
Michel
M
D000818:Animals; D004195:Disease Models, Animal; D005684:Gait / Q000502:physiology; D035002:Lower Extremity / Q000293:injuries* / Q000294:innervation* / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation* / Q000473:pathology* / Q000503:physiopathology; D009416:Nerve Regeneration / Q000502:physiology; D051381:Rats; D011917:Rats, Inbred Lew; D020127:Recovery of Function / Q000502:physiology; D015203:Reproducibility of Results; D012584:Sciatic Nerve / Q000293:injuries* / Q000473:pathology* / Q000503:physiopathology; D013997:Time Factors