EVALUATION OF 3-DIMENSIONAL MRI EXPLORATION OF PROLACTIN-SECRETING MICROADENOMAS

Over an 8-month period (July 1990-to February 1991), we explored 21 wo men presenting with a clinical and laboratory profile of prolactin-sec reting microadenoma of the pituitary gland. Magnetic resonance imaging (MRI) is undoubtedly the most efficient method to explore microadenom as, especially when carried out in the absence of any treatment. In 8 cas, MRI was performed in the absence of medical treatment and gave a positive result, i.e. always showed a focal lesion. In the remaining 1 3 cases the patients had been treated before the exploration, and MRI detected a microadenoma in only 4 cases. The duration of treatment and the time elapsed between its withdrawal and the MRI examination did n ot seem to influence the postivity or negativity of the imaging result s. Among the 9 cases where MRI failed to show a focal lesion, the imag e was normal in 3 cases and displayed an arachnoidocele in 3 cases ; t he pituitary gland was convex and homogeneous in 1 case and convex and heterogenous in 3 cases, which raised the problem of the effects of b romocriptine on the MRI images. As regards signals, in 5 cases the mic roadenoma was hyperintense on the spin-echo sequence without contrast injection; it was undetectable on the same sequence in 2 cases. In 4 c ases the lesion was contrast-enhanced after gadolinium injection. Usin g millimetric sections enables. small-size adenomas (2.5 x 3 mm) to be visualized.