In vivo detection of severity of optic nerve crush using manganese-enhanced magnetic resonance imaging in rats

Abstract

Background Traumatic optic neuropathy (TON) is one of the reasons for permanent vision loss. Currently, the clinical practices may not be sufficient for direct assessments and comprehensively determining the location and extent of the patients with optic nerve injury in traumatic optic neuropathy. Magnetic resonance imaging (MRI) provides a non-invasive option. However, rare reports have found whether the differentdegree of injury of the optic nerve can be detected by manganese-enhanced MRI (MEMRI). This study aimed to explore the efficacy of MEMRI in the visual pathway for different severity of opitic nerve injury in rats. Methods The different injuries of mild, moderate, and heavy damages were created by modified reverse tweezer and were evaluated by counting retinal ganglion cells (RGCs) and VEP ananlysis. Sprague-Dawley (SD) rats were intravitreally injected with 2 l of 25 mmol/L MnCl2, which has been confirmed as a safe injection concentration. The contrast-to-noise ratio (CNR) of MEMRI for optic nerve enhancement at different injury levels was measured. Results The location of the significantly decreased signal point on optic nerve (ON) was corresponding to the location we made. However, similar findings are not obvious, or even have not been observed in 28 days in each group and also in 14 days at F100 group, indicating that MEMRI could be directly intuitive positioned in the early stage on the optic nerve injury. Conclusions The possibility of using MEMRI in optic nerve injury in a safe injection concentration of 25 mmol/L is confirmed. Therefore, it is possible to detect the severity of the optic nerve by MEMRI examination.