A Case of Syndrome of Inappropriate Scretion of Anti-Diuretic Hormone Associated with Sodium Valproate
A 55-year-old man was admitted to hospital with seizure and confusion. He had suffered from generalized tonic clonic epilepsy that occurred after a craniectomy due to right epidural hematoma. The patient was treated with sodium valproate in a dose of 900 mg/day for 9 months. He had been removed a brain tumor 4 years before and he had craniectomy for an epidural hematoma 10 months ago. He was admitted to our hospital with a reported seizure, dizziness, nausea and vomiting for the day.\nHis vital signs, physical and neurological examination on arrival were within normal limits except drowsy consciousness. He appeared euvolemic without evidence of congestion or dehydration. An electroencephalography showed slow background activity with no evidence of epileptiform discharges. Mild bilateral cortical atrophy was observed on magnetic resonance imaging of the brain. Significant laboratory findings were: sodium of 111 (135-145) mmol/l , potassium of 2.6(3.5-5.0) mmol/l, chloride 66 (95-110) mmol/l and serum osmolarity of 245 (280-300) mosm/kg. Urine sodium and urine osmolarity were 58 mmol/l and 751 (50-1,200) mosm/kg, respectively.\nAnte meridiem cortisol level, thyroid stimulating hormone, and free thyroxine level were within normal limits. The results of her rapid ACTH stimulation tests were also within normal ranges (). Valproic acid level was revealed to be within therapeutic range (62.76 µg/ml; an optimum therapeutic range 50 to 100 µg/ml). After she was discharged, she did not restrict her water consumption.\nThe diagnosis of SIADH was made based on hyponatremia, and low serum and high urine osmolality. No other causes of hyponatremia, including diuretic therapy, tumors and respiratory system disease, were present. The sodium valproate treatment was discontinued, and hypertonic saline was infused because of his symptomatic and profound hyponatremia. His serum sodium concentration increased to 131 mmol/l over 48 hours with the use of hypertonic saline. The symptoms resolved immediately after the correction of hyponatremia. During the next 48 hours, normal saline infusion was given, and serum sodium level was restored to 134 mmol/l. Serum sodium concentration was maintained at 134-136 mmol/l after stopping saline infusion and VPA (). Lamotrigine was prescribed and he was subsequently discharged. The follow-up sodium levels for 3-weeks and 6-months after discharge were normal.