Manganese-enhanced MRI Offers Correlation with Severity of Spinal Cord Injury in Experimental Models
Nikolay L. Martirosyan1, Gregory H. Turner2, Jason Kaufman3, Arpan A. Patel1, Evgenii Belykh1, 4, M. Yashar S. Kalani1, Nicholas Theodore1, Mark C. Preul*, 1
1 Departments of Neurosurgery, Barrow Neurological Institute St. Joseph’s Hospital and Medical Center Phoenix, Arizona,USA
2 Center for Preclinical Imaging, Barrow Neurological Institute St. Joseph’s Hospital and Medical Center Phoenix, Arizona, USA
3 Department of Anatomy, Midwestern University Glendale, Arizona, USA
4 Irkutsk Scientific Center of Surgery and Traumatology, Irkutsk, Russia
Spinal cord injuries (SCI) are clinically challenging, because neural regeneration after cord damage is unknown. In SCI animal models, regeneration is evaluated histologically, requiring animal sacrifice. Noninvasive techniques are needed to detect longitudinal SCI changes.
To compare manganese-enhanced magnetic resonance imaging (MRI [MEMRI]) in hemisection and transection of SCI rat models with diffusion tensor imaging (DTI) and histology.
Rats underwent T9 spinal cord transection (n=6), hemisection (n=6), or laminectomy without SCI (controls, n=6). One-half of each group received lateral ventricle MnCl2 injections 24 hours later. Conventional DTI or T1-weighted MRI was performed 84 hours post-surgery. MEMRI signal intensity ratio above and below the SCI level was calculated. Fractional anisotropy (FA) measurements were taken 1 cm rostral to the SCI. The percentage of FA change was calculated 10 mm rostral to the SCI epicenter, between FA at the dorsal column lesion normalized to a lateral area without FA change. Myelin load (percentage difference) among groups was analyzed by histology.
In transection and hemisection groups, mean MEMRI ratios were 0.62 and 0.87, respectively, versus 0.99 in controls (P<0.001 and P<0.001, respectively); mean FA decreases were 67.5% and 40.1%, respectively, compared with a 6.1% increase in controls (P=0.002 and P=0.019, respectively). Mean myelin load decreased by 38.8% (transection) and 51.8% (hemisection) compared to controls (99.1%) (P<0.001 and P<0.001, respectively). Pearson’s correlation coefficients were -0.94 for MEMRI ratio and FA changes and 0.87 for MEMRI and myelin load.
MEMERI results correlated to SCI severity measured by FA and myelin load. MEMRI is a useful noninvasive tool to assess neuronal damage after SCI.
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* Address correspondence to this author at the Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, 350 W. Thomas Rd.; Phoenix, AZ 85013, USA; Tel: 602.406.3593; Fax: 602.406.4104; E-mail: Neuropub@dignityhealth.org