SUN-411 Isolated Central Diabetes Insipidus Due to Astrocytoma: A Case Report

Central diabetes insipidus (CDI) is characterized by a decreased release of antidiuretic hormone (ADH) resulting in a variable degree of polyuria. Patients with central nervous system lesions an impaired thirst mechanism can lead to moderate to severe hypernatremia can develop. Here we report a case of CDI cause by an astrocytoma tumor. This is a 64 year-old female who was found to have multiple cerebellar lesions in MRI as part of dizziness work up. She was admitted to undergo brain biopsy. She became polyuric during the procedure and the immediate post-operative time. Her thirst mechanism was impaired by the anesthesia. Serum sodium increased from 142 to 166 mmol/L (135-146) with a serum osmolality 326 mOsm/kg (275-295), urine specific gravity 1.002 and urine osmolality 131mOsm/kg consistent with diabetes insipidus (DI). The patient received 1mcg of demopressin with resolution of polyuria, polydipsia as well as hypernatremia confirming CDI. Further assessment of the anterior pituitary axis was within normal limits. In the light of the clinical findings, a second review of the imaging confirmed the presence of a pituitary stalk with mild diffuse thickening without nodularity. She eventually recovered her thirst mechanism and her urine output was adequate despite not receiving desmopressin for more than 48 hours. Final pathology revealed Brain astrocytoma, for which she was started on temozolamide. Patient was readmitted a month later with altered mental status, she was found to have an urinary track infection and hypernatremia due to worsening CDI requiring demopressin on the clock. Repeating imaging revealed significant parenchymal disease and leptomenigeal disease affecting the sella, stalk and hypothalamic regions. A wide range of lesions can present as isolated thickening of the pituitary stalk. We could only find 5 other cases of patients with astrocytoma who debuted with isolated CDI. Interestingly we found that Temozolamide has been reported as a rare cause of CDI with only 3 cases reported in the literature, but in our patient CDI was confirmed prior to initiation of chemotherapy.