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Findings: There are extensive regions of abnormally high signal on the FLAIR axial images in the bilateral occipital lobes as well as the bilateral posterior temperoparietal region as well as small areas of hyperintensity within the bifrontal region. These regions of abnormal hyperintensity involve both the subcortical white matter as well as the cortical gray matter.
Diagnosis: Cyclosporine related neurotoxicity.
Discussion: Although cyclosporine has been known to be nephrotoxic for quite some time, its neurotoxic effects are now only recently being described. Cyclosporine is an immunosuppressant which in recent studies has been described as causing a neurotoxic side effect in approximately 10% of patients undergoing therapy. The characteristic findings of cyclosporine induced neurotoxicity include cortical hyperintensity on MR images commonly involving the cingulate gyrus as well as the occipital lobes, with less common involvement of the parietal and frontal lobe. In addition to the cortical hyperintensities, many studies describe subcortical white matter involvement with diffuse hyperintensities. These regions of increased signal intensity are most apparent on proton density (or FLAIR) weighted images.
Although the cyclosporine related neurotoxicity has been demonstrated more commonly in patients with elevated blood levels of cyclosporine, there have been reported cases at which time the blood levels of cyclosporine were found to be therapeutic.
The exact type of physiology of the cyclosporine induced neurotoxicity is not entirely understood, but is felt to most likely represent regions of cyclosporine induced blood flow reduction in the small pial vessels with resultant cortical ischemia. Subsequently, in more severe cases, the decreased perfusion extends into the subcortical region with resulting hyperintensity. Follow-up MR after sessation of cyclosporine therapy generally reveals complete resolution of the abnormalities. In addition, clinical improvement coincides with the resolution of the abnormalities identified on MRI.
References:
Jansen O. Cortical Hyperintensity on Proton Density Weighted Images.
An MRI Sign of Cyclosporine Related Encephalopathy. American Journal
of Neuroradiology. 1996;17:337-344.
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