Infections of the central nervous system in transplant recipients.

Central nervous system (CNS) infections, accounting for 4-29% of CNS lesions in transplant recipients, are a significant post-transplant complication. Focal CNS infectious lesions or brain abscesses have been documented in 0.36-1% of the transplant recipients. Mycelial fungi, particularly Aspergillus, are by far the most frequent etiologies of post-transplant brain abscesses. Bacteria, with the exception of Nocardia, are rarely associated with brain abscesses in transplant recipients. Time of onset and concurrent extraneural lesions have implications relevant towards invasive diagnostic procedures in transplant recipients with brain abscesses. Meningoencephalitis in transplant recipients is predominantly due to viruses, e.g., herpesviruses, and less frequently due to Listeria monocytogenes, Toxoplasma gondii, and Cryptococcus. Despite a wide, and at times perplexing array of opportunistic pathogens that can cause CNS infections, the temporal association of the infection with the time elapsed since transplantation, risk factors, clinical manifestations, and neuroimaging characteristics of the lesion can allow a reasoned and rational approach towards the recognition, diagnosis, and appropriate management of CNS infections in transplant recipients.