Infection of the central nervous system in organ transplant recipients

Infections of the central nervous system are an important cause of morbidity and mortality in recipients of organ transplants. Three organisms--Listeria monocytogenes, Aspergillus fumigatus, and Cryptococcus neoformans--account for the great majority of such infections. The incidence of these infections is directly related to the patient's net state of immunosuppression and to the epidemiologic exposures he encounters. There is an expected timetable of when particular infections are likely to occur post-transplant. The most important factor in effecting patient survival is the rapidity with which diagnosis is made. Because of the nature of the infecting organisms and the impaired inflammatory response, the clinical presentation of CNS infection is often insidious, making early diagnosis difficult. However, an aggressive approach based upon lumbar puncture and CT scanning for patients with headache and fever or altered states of consciousness can be very rewarding. In addition, the use of such ancillary clues as the results of skin and lung biopsies can be an important clue to disseminated infection, particularly involving the CNS. The recent deployment of the MRI scan in immunosuppressed patients with unexplained CNS symptoms holds particular promise for early diagnosis.