Magnetic resonance imaging as a non-invasive method to assess pyramidotomy

Spinal cord injury is a neurological and pathological state that causes motor, sensory and autonomic dysfunction. The corticospinal tract (CST) is one of the main motor tracts in the spinal cord, so damaging it causes a loss of fine motor movements and dexterity. The mouse model of unilateral pyramidotomy allows the study of compensatory sprouting in the CST axons. However, to date, surgery confirmation can only be performed postmortem using immunofluorescent staining. Prognosis biomarkers can help optimize animal care and minimize pain and suffering. In this context, magnetic resonance imaging (MRI) is an effective tool that allows for the comprehensive and non-invasive assessment of the progression of different types of CNS lesions. Moreover, in vivo preclinical CNS models can be used as their own control in longitudinal studies.

In this preclinical study, we proposed the use of MRI to assess the outcome of pyramidotomy surgery in C57BL/6 mice (n = 21). We examined the volume and T2-signal in the area occupied by the dorsal column (DC). We found non-significant changes, with none in the volume nor the T2-signal at any post-injury week. Then, knowing that the CST is a small tract in the DC, we measured the area occupied by the CST within the DC. Interestingly, we observed a general reduction in volumes, which was statistically significant at 7 days post-injury. On the other hand, we observed a decrease in the T2-signal following injury that was statistically significant from 14 days post-injury onward.

In conclusion, these results indicate that MRI could be a suitable tool to detect slight changes in the T2-signal in small regions in an earlier way to predict the efficacy of the surgery.