Endocrine Abstracts

Introduction: Rapid correction of hyponatremia is known to cause central pontine myelinolysis. It may concurrently involve other areas of brain as well, referred as extra-pontine myelinolysis (EPM). Isolated EPM however is a very rare occurrence. We present a case of EPM where the hyponatremia was secondary to syndrome of inappropriate antidiuretic hormone secretion (SIADH) after surgery for a pituitary macroadenoma.

Case report: A 36-year-old man underwent transsphenoidal surgery for a non-functional 2.4×2.6×1.8 cm pituitary macroadenoma causing chiasmatic compression. During the immediate postoperative period, the patient developed polyuria and received desmopressin. Six days after surgery, he left the hospital asymptomatic receiving hydrocortisone. Diuresis volume was normal and desmopressin was not necessary anymore. On the 8th postoperative day, his level of consciousness decreased and suffered from seizure requiring intubation. Blood examination revealed severe hyponatremia (serum sodium level of 108 mEq/l) and 1 day later serum sodium increased rapidly to 135 mEq/l. On the 16th postoperative day, orotracheal intubation was discontinued but the patient was unable to communicate. Physical examination revealed global hyperreflexia, clonus, dysarthria and gait disturbance. Head MRI on the 18th postoperative day demonstrated intense high-signal bilateral lesions in corpus striatum on FLAIR and DWI, and extrapontine myelinolysis was diagnosed. The patient’s symptoms improved gradually after rehabilitation and antispasticity treatment. It was suggested that the changes in serum sodium levels after pituitary surgery were due to SIADH due to degeneration of nerve terminals in the posterior pituitary.

Conclusions: Incidence of hyponatraemia following pituitary surgery is reported between 3 and 25%. The delay in onset of SIADH can lead to practical problems for neurosurgical units where there is very early discharge following pituitary surgery. As pituitary surgery may trigger changes in serum sodium leading to myelinolysis, this possibility should always be borne in mind when treating such patients.