MRI in seven cases of tacrolimus (FK-506) encephalopathy: utility of FLAIR and diffusion-weighted imaging

Area of Science:

• Neuroimaging
• Toxicology
• Nephrology

Background:

• Tacrolimus (FK-506) is an immunosuppressant frequently used in organ transplantation.
• FK-506 toxicity can manifest as encephalopathy, a serious neurological complication.
• Understanding the imaging characteristics and potential triggers of FK-506 encephalopathy is crucial for patient management.

Purpose of the Study:

• To evaluate the utility of fluid-attenuated inversion-recovery (FLAIR) and diffusion-weighted imaging (DWI) in diagnosing tacrolimus (FK-506) encephalopathy.
• To determine if clinical and imaging data can predict the cause of FK-506 encephalopathy.
• To compare imaging findings in FK-506 encephalopathy with those of cyclosporin A (CsA) toxicity.

Main Methods:

• Retrospective analysis of MRI scans (FLAIR and DWI) in seven patients with suspected FK-506 toxicity.
• Correlation of imaging findings with clinical data, including serum FK-506 levels and electrolyte/fluid balance.
• Comparison of MRI findings with historical data from cyclosporin A (CsA) toxicity.

Main Results:

• Areas affected by FK-506 toxicity on MRI were similar to those seen in CsA toxicity.
• Abnormal signals were most consistently detected on FLAIR sequences in all patients.
• Diffusion abnormalities were detected in only one of four patients who underwent DWI, showing increased diffusion in deep white matter.
• Five of six patients with available clinical data experienced sudden electrolyte or fluid equilibrium disturbances preceding or coinciding with neurological symptoms.

Conclusions:

• FLAIR MRI is highly sensitive for detecting abnormalities in FK-506 encephalopathy.
• Imaging findings in FK-506 encephalopathy resemble those of CsA toxicity.
• Disturbances in electrolyte and/or fluid equilibrium may act as a trigger for FK-506 encephalopathy in individuals with adequate tacrolimus serum levels.