NORMAL MR APPEARANCES OF THE POSTERIOR PITUITARY IN CENTRAL DIABETES-INSIPIDUS ASSOCIATED WITH SEPTO-OPTIC DYSPLASIA

Magnetic resonance (MR) imaging of the pituitary in children with cent ral diabetes insipidus usually shows absence of the normal high signal within the posterior gland, The high signal of the normal posterior p ituitary is thought to be due to the presence of intracellular storage granules of vasopressin. MR imaging has been advocated as a useful in vestigation to aid in the distinction between central diabetes insipid us and other causes of thirst and polydipsia. We report the case of an infant with central diabetes insipidus in association with septo-opti c dysplasia in whom MR imaging showed normal appearances of the poster ior pituitary, The mechanism of central diabetes insipidus in this cas e may be related to a failure of hypothalamic function affecting osmor eception, rather than to a deficiency of vasopressin. Normal MR appear ances of the pituitary do not exclude central diabetes insipidus in in fants with midline cerebral malformations.