Recurrent Triphasic Central Diabetes Insipidus After Transsphenoidal Surgery

This patient developed triphasic diabetes insipidus (DI) after undergoing transsphenoidal surgery. This postsurgical complication includes a transitory DI, followed by SIADH, and then permanent DI. He underwent a second trans-sphenoidal resection due to tumor recurrence and again presented with a triphasic response pattern in the post-operative period, which is unusual.

Case Description:

A 32-year-old male with one-year history of headaches and blurred vision was found to have a 4-cm cystic-solid suprasellar mass, optic chiasm compression and obstructive hydrocephalus. He underwent right frontal craniotomy with endoscopic resection of the mass. On postoperative day (POD) 1, he developed central DI followed by SIADH. On POD 7 he developed persistent adipsic DI and secondary panhypopituitarism. Pathology showed an adenoma. Levothyroxine, testosterone, hydrocortisone, and desmopressin replacement were started.

Nine months postoperatively, surveillance MRI showed recurrence with a 1 cm suprasellar cystic lobule abutting the optic chiasm. He underwent transsphenoidal resection of the mass. Pathology showed negative immune-peroxidase stain adenoma. Preoperative labs showed serum sodium: 140 mmol/L (ref 135-145), serum osmolality (osm): 287 mOs/Kg (ref 280-300), urine osm: 159 mOs/Kg (ref 200-1200), serum cr: 0.8 (ref 0.5-1.2).

On POD 2, while on his levothyroxine, hydrocortisone, and desmopressin replacement, serum sodium increased to 150 mmol/L and urine osmolality to 506 mOs/Kg. He was maintained on 600 mcg desmopressin daily in 2 divided doses. However, on POD 5, serum sodium decreased to 130 mEq/L with urine osm 708 mOs/Kg. Concerned for SIADH, his desmopressin was held. On POD 6, serum sodium decreased further to 116 mmol/ L; thus, fluid restriction was started.

On POD 7, still on fluid restriction and without desmopressin administration, his serum sodium improved to 142 mmol/L. It continued to increase prompting resumption of desmopressin and liberalization of free water intake. His urine output averaged 3 to 4 liters per day.

Discussion:

Triphasic DI after pituitary surgery suggests early hypothalamic dysfunction with an initial decreased release of vasopressin (AVP), followed by an outpouring of stored AVP from the degenerating pituitary, followed by definitive AVP depletion. Our case suggests that the posterior pituitary gland may have some residual AVP secretory function and manual manipulation, caused another outpouring of stored AVP, inducing triphasic pattern of initial DI followed by SIADH and finally DI. A repeat triphasic pattern when managing patients with known DI who are undergoing repeat pituitary surgery is unexpected.