Persistent hypernatremia secondary to diabetes insipidus in craniopharyngioma, a case discussion Bipin Thapa, MD, Anuj Shrestha, MD, Prajwol Pant, MD, Najindra Maharjan, MD, Sanjay Bhandari, MD, Paula Butler, MD. . Discussion: Diabetes insipidus is a heterogeneous condition characterized by polyuria and polydipsia caused by a lack of secretion of vasopressin(central DI), its physiological suppression following excessive water intake, or kidney resistance to its action(nephrogenic DI).2 Central diabetes insipidus (DI) can be the outcome of a number of diseases that affect the hypothalamic-neurohypophyseal axis.3 The causes of the condition can be classified as traumatic, inflammatory, or neoplastic. Traumatic causes include postoperative sella or transection of the pituitary stalk, while infectious or inflammatory causes include meningitis, lymphocytic hypophysitis, and granulomatous inflammations such as sarcoidosis and Wegener's granulomatosis. Various neoplastic conditions such as germinoma, Langerhans cell histiocytosis, metastasis, leukemic infiltration, lymphoma, teratoma, pituitary adenoma, craniopharyngioma, Rathke cleft cyst, hypothalamic glioma, and meningioma are also causes of central DI.3 In affected patients, careful analysis of these MR imaging features and correlation with the clinical manifestations can allow a more specific diagnosis, which is essential for treatment. Craniopharyngiomas are rare, usually suprasellar, solid or mixed solid-cystic benign tumors that arise from remnants of Rathke's pouch along a line from the nasopharynx to the diencephalon.4 Therapeutic options for patients with craniopharyngioma include surgery – transcranial versus transsphenoidal, radiation therapy (RT), and the combination of the two. RT alone is usually restricted to patients with very small tumors, while the optimum extent of surgery remains controversial. Diabetes insipidus was the most common deficiency associated with surgery; the overall percentage of patients with diabetes insipidus increased from 16 to 66 percent and from 23 to 69 percent after transcranial and transsphenoidal surgery, respectively.5 Introduction Central diabetes insipidus is one of the common complications after surgery for craniopharyngioma, presenting in 70-90% of patients.1 As compared to this, preoperative central diabetes insipidus secondary to compression is less common. Incidence of central diabetes insipidus ranges from 8 to 35 percent in patients with craniopharyngioma.1 We report a case of persistent hypernatremia secondary to central diabetes insipidus in a patient with diagnosed craniopharyngioma before surgery. Case description A 37 year old female with known type 2 diabetes mellitus and craniopharyngioma, presented to the ED with altered mental status, polyuria, poydypsia and generalized weakness after she missed her insulin for a day. At presentation her blood glucose was 733mg/dl, serum sodium 161meq/l and serum osmolality was 379 mosm/kg. Her serum and urine ketone was negative. She was admitted to intensive care unit with the diagnosis of hyperosmolar hyperglycemic non ketotic state. She was managed with IV fluids and insulin drip for this and she was given prednisone and levothyroxine for her panhypopituitarism. CT scan and MRI of the head did not show any interval increase in the size of the craniopharyngioma. Even with generous IV fluid repletion, she had persistent hypernatremia. With the possibility of central diabetes insipidius, she was given a dose of vasopressin. Her urine osmolality increased to more than 500 and there was an improvement in serum sodium to 147meq/l. A diagnosis of central diabetes insipidus was made and she was started on desmopressin acetate nasal spray 10 mcg at night time. Her serum sodium gradually normalized to 140meq/l, with a serum osmolality of 297mosm/kg and urine osmolality of 458mosm/kg. Symptoms of polyuria and polydypsia can be due to diabetes mellitus or diabetes insipidus, so it is important to be aware of the possibility of central diabetes insipidus in a patient with craniopharyngioma even before surgery if a patient presents with persistent hypernatremia like in our case. References: Ghirardello S, Hopper N, Albanese A, Maghnie M. Diabetes insipidus in craniopharyngioma: postoperative management of water and electrolyte disorders. J Pediatr Endocrinol Metab. 2006 Apr;19 Suppl 1:413-21. Review. Maghnie M. Diabetes insipidus. Horm Res. 2003;59 Suppl 1:42-54. Review. Shin JH, Lee HK, Choi CG, Suh DC, Kim CJ, Hong SK, Na DG. MR imaging of central diabetes insipidus: a pictorial essay. Korean J Radiol. 2001 Oct-Dec;2(4):222-30. Review. Petito, CK, DeGirolami, U, Earle, KM. Craniopharyngiomas. A clinical and pathological review. Cancer 1976; 37:1944 Honegger, J, Buchfelder, M, Fahlbusch, R. Surgical treatment of craniopharyngiomas: Endocrinological results. J Neurosurg 1999; 90:251.