[MRI aspects of central nervous system sarcoidosis]

Sarcoidosis is a multisystemic disease of unknown origin characterized pathologically by the presence of noncaseating epithelioid granulomas. Symptomatic involvement of the CNS may develop in a patient with known sarcoidosis or it may be the initial manifestation. Intracranial sarcoidosis may include meningeal disease, cranial neuropathy, hypothalamic and pituitary dysfunction and both intraaxial and extraaxial mass. The MRI features are variable and non specific, so differentiation from other lesions (multiple sclerosis, tumour, meningitis, vasculitis) may be difficult, especially in the absence of extracranial disease. Patients with symptoms usually have corresponding CNS lesions at MR imaging, except for cranial nerves involvement. Under therapy, resolution of lesions at MR imaging lags behind resolution of clinical symptoms. MRI may contribute to confirm a clinically suspected diagnosis or detect subclinical involvement. MRI is also very helpful for follow-up under therapy.