Tuberculosis and sarcoidosis may involve the CNS, producing suprasellar masses or thickening of the infundibulum or optic chiasm. These granulomatous lesions are usually isointense with grey matter on T1-weighted MR images. Enhancement of the parenchymal lesions, as well as leptomeningeal enhancement are seen following contrast administration (Fig. 24.21). Other causes of infundibular thickening include lymphoma, metastatic carcinoma, and Langerhans' cell histiocytosis.
Fig. 24.21 Sarcoidosis: magnetic resonance imaging. Coronal T1-weighted image following contrast administration shows a thickened, enhancing infundibulum typical of CNS granulomatous disease. Enhancement in both sylvian fissures identifies leptomeningeal involvement.
