Brain perfusion imaging in asymptomatic patients receiving cyclosporin

Cyclosporin has neurotoxic effects in a significant number of transplant patients that are associated with characteristic findings on MR images. Focal abnormalities in cerebral perfusion have been implicated in the pathophysiology of cyclosporin neurotoxicity. In the clinically asymptomatic patient, however, it is not known whether any imaging evidence of cyclosporin's effect on the brain is demonstrable. Our hypothesis was that conventional MR imaging, perfusion MR imaging, and single-photon emission CT (SPECT) could enable detection of subclinical lesions in asymptomatic patients. The ability to detect such lesions might aid in the identification of persons most at risk for clinical neurotoxicity.

Ten posttransplant patients being treated with cyclosporin were recruited prospectively. Imaging studies were performed within 3 weeks of transplantation. Patients were examined with MR imaging, using standard spin-echo and dynamic contrast-enhanced perfusion techniques, and SPECT scanning. Postprocessing of MR perfusion data was performed to obtain pixel-by-pixel maps of regional cerebral blood volume, peak height, and time-to-peak parameters.

The mean age of the patients was 45 +/- 11 years. At the time of imaging, three patients had minor neurologic manifestations commonly associated with cyclosporin (ie, mild tremor, headache), but no patient had clinical neurotoxicity. Findings on conventional MR images, MR perfusion maps, and SPECT perfusion scans were normal in all patients.

Conventional MR imaging, dynamic perfusion MR imaging, and SPECT do not depict any lesions in asymptomatic patients on cyclosporin. Therefore, it may not be possible for imaging methods to aid in the identification of patients at risk for neurotoxicity. Our findings support previously published conclusions that the lesions visible in patients with clinical neurotoxicity are due to cyclosporin effects and not to preexisting coincidental abnormalities.