Magnetic resonance imaging is a method of choice for the diagnosis of microprolactinomas. Using a Phillips Gyroscan NT 15 (1.5 T), 42 patients whose clinical history and serum prolactin levels were compatible with the diagnosis of prolactinomas were examined. Four patients (3 male and 1 female) with macroadenoma were investigated and excluded, while microprolactinoma was found in the other 38 (32 female and 6 male) patients. Imaging features were similar in all microprolactinomas--hypointensity up to 10 mm in size in T1 weighted images, only sometimes, in the case of a cystic or a hemorrhagic component, also registered in T2 weighted images. Deviation of the pituitary stalk was present in 19 of the 38 patients (16 with microprolactinoma, 3 without any detectable lesion). Convex upper limit of the gland was demonstrated in 17 subjects (16 microprolactinomas, 1 without detectable lesion). Pituitary adenoma is not the only cause of raised serum prolactin level. This can be a consequence of medication, spinal cord tumor, compression of the pituitary stalk, hypothyroidism or a lesion in dermatomes T3 to T5 (mammary gland level). Results from imaging must always be assessed in the light of the patient's clinical history and biochemical parameters.

Department of Neurology Charles University Prague Czech Republic