Development of Inappropriate Vasopressin Secretion in Association With Lumbar Cerebrospinal Fluid Drainage in an Adult With Traumatic Basilar Skull Fracture

OBJECTIVE: Hyponatremia associated with cerebrospinal fluid (CSF) drainage is primarily limited to pediatric patients. Only 1 case in an adult, after pituitary surgery, has been described. We present the first adult case, to our knowledge, of lumbar CSF drainage associated with the syndrome of inappropriate antidiuretic hormone (SIADH) in a patient with a traumatic basilar skull fracture. METHODS: Serum and urine samples were evaluated for hyponatremia. Computed tomography and magnetic resonance imaging were performed to evaluate the fractures. RESULTS: A 31-year-old woman was hospitalized with traumatic facial and skull base fractures and managed conservatively. Four days into her hospital stay, she underwent lumbar CSF drainage for 6 days to treat a CSF leak. On examination, the patient remained hemodynamically stable and euvolemic. Sodium levels decreased from 142 to 136 mmol/L (normal, 135-146 mmol/L) on the day before and after lumbar drain placement, respectively, down to a nadir of 124 mmol/L over 3 subsequent days. Serum osmolality was 260 mOsm/kg (275-295 mOsm/kg); urine osmolality, 482 mOsm/kg; urine Na, 175 mmol/L; and thyroid-stimulating hormone, 4.0 μIU/mL (0.3-4.7 μIU/mL). The patient received treatment with sodium tablets, fluid restriction, and hypertonic saline for a diagnosis of SIADH. Sodium levels normalized from 131 to 136 mmol/L within 16 hours after lumbar drain removal. CONCLUSION: This case illustrated a temporal association of SIADH with CSF drainage in an adult. Although this could be coincidental because a basilar skull fracture can lead to SIADH, it raises the possibility that CSF lumbar drainage contributed to the patient’s SIADH.