Purpose:
Cerebral excitotoxic injury leads to acute decrease of apparentdiffusion coefficient (ADC) detected by in vivo diffusion MRI.We examined the feasibility of detecting retinal excitotoxicinjury using the same technique.
Methods:
Forty-five 2-month old male C57BL/6 mice were imaged in vivoat 11.7T followed by cross-sectional histology using previouslyreported method1. Each mouse was examined at baseline, 3-hour,1-, 3-, or 7-day post intravitreal injection of 0.5uL 5mM NMDAor 0.5uL saline (n>=5 for each group except n=3 for saline3- and 7-day). The ADC map was calculated from diffusion weightedimages. The three MR-detected retinal layers were respectivelyassigned to NFL/GCL/IPL, INL/OPL, and ONL/IS/OS.
Results:
NMDA excitotoxicity resulted in substantial retinal swellingat 1-day (Fig. 1). However, an acute increase of inner retinaldiffusion weighted MR signal (Fig 1) reflecting a 30% decreaseof ADC in INL/OPL (Fig. 2) was observed as early as 3-hour,consistent with previous report in cerebral cytotoxic edema.ADC in NFL/GCL/IPL exhibited a transient increase suggestingdeath of ganglion cells that are sensitive to NMDA excitotoxicity.ADC in ONL/IS/OS was unchanged at all times because the pre-synapticphotoreceptor cells are resistant to NMDA excitotoxicity.
Conclusions:
Decreased ADC was observed before detectable retinal swellingin NMDA induced retinal excitotoxic injury.1.Chen J et. al,Magn Reson Med, 2008
Keywords: retina • edema • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)