MR OF THE PITUITARY IN PATIENTS WITH PRADER-WILLI-SYNDROME - SIZE DETERMINATION AND IMAGING FINDINGS

Prader-Willi syndrome (PWS) is an unusual genetic disorder characteriz ed by short stature, obesity, hypogonadism, hypotonia, cognitive impai rment, and dysmorphic facies. There is an interstitial deletion of the proximal long arm of chromosome 15 in about 70% of patients. Some of these clinical features suggest a central hypothalamic/pituitary dysfu nction, and recent investigations have demonstrated a marked impairmen t in spontaneous growth hormone (GH) secretion. We studied 15 GH-defic ient PWS patients by magnetic resonance imaging (MRI) to determine whe ther there was a diminution in the gross morphological size of the ant erior pituitary gland, the site of GH synthesis. We also set out to ca talog the pertinent imaging findings in this patient population. Our r esults indicate that this is the first report documenting pituitary si ze by MRI in PWS patients. No statistically significant difference was found in the height of the anterior pituitary gland in PWS patients c ompared with either normal, children or children with isolated GH defi ciency. An interesting imaging finding is that three of 15 patients (2 0%) demonstrated complete absence of the posterior pituitary bright sp ot (PPBS), and a fourth patient demonstrated a small PPBS. These obser vations reflect an objective physiologic disturbance in the hypothalam us. The clinical and radiologic implications of these findings are dis cussed.