Introduction: Certain neurological complications may be seen before liver and renal transplantation and are diagnosed by brain CT and MRI. After organ transplantation most of them may disappear, some of them insist or new complications may arise, mostly due to immunosuppressive therapy. Prompt diagnosis of neurological complications are important to plan the appropriate treatment. Brain Computed Tomography (CT) which is the primary imaging modality is not sufficient in most of the cases. Brain Magnetic Resonance Imaging (MRI) and diffusion-weighted imaging should be done in such cases. Our aim is to show examples of CT and MRI findings of neurological complications after liver and kidney transplantation.
Materials and Methods: We retrospectively evaluated patients who had neurological complications after liver or kidney transplantation.  Brain CT and MRI studies are retrieved from the Picture Archiving and Communication System (PACS). Neuroradiological findings can be classified in three groups; as complications due to primary parenchymal disease, due to transplantation or as incidental findings.
Results: Symptoms of patients were seizures, altered mental status, confusion, unconsciousness, headache, visual hallucinations, motor deficit, nausea and vomiting.  Diffuse vasogenic brain edema, acute stroke, intracranial hemorrhage and posterior reversible encephalopathy syndrome (PRES) are commonly seen short-term neurological complications. Vasogenic brain edema and intracranial hemorrhage can be diagnosed on brain CT. Acute stroke can be diagnosed on diffusion-weighted imaging. PRES, which is seen commonly after transplantation is caused by immunosuppression or hypertension. Vasogenic edema is seen mostly within the bilateral parietal and occipital regions. Aspergillosis, rhinocerebral mucormycosis, toxoplasmosis, tuberculosis, bacterial abscess, viral encephalitis are the opportunistic infections which can be seen after transplantation.  Aspergillus brain abscesses are seen as solitary or multiple ring enhancing lesions in gray white matter junction with central diffusion restriction on brain MRI. Aspergillus spondylodiscitis which is rare in transplant patients, can be seen as discitis, epidural abscess and subchondral T2 hypointense band on lumbar MRI. Also because of immunosuppression, posttransplant brain tumor risk increases 3-4 times more than the normal population. Posttranplant lymphoproliferative disorder may be seen after solid organ transplantation.
Conclusion: Neurological complications are not rare after liver and kidney transplantation. Brain CT is the primary imaging modality to rule out intracranial hemorrhage. Brain MRI with diffusion-weighted imaging should be done if brain CT is insufficient and in the presence of serious symptoms. Prompt imaging is very important to establish the certain diagnosis and for achievement in treatment.