A 30 y.o. woman was a passenger in an SUV that was rear ended. Airbags deployed and she had amnesia for three hours. Her head ct is shown below at the time of the accident.

After being in the heat over the 4th of July she was found down seizing at home. What could be wrong?

Hint: the CT is normal.

Our patient had a sodium of 114.  She was thought to have Cerebral salt wasting caused by her concussion. She was treated initially with hypertonic saline and then NS with gradual improvement in her Na.   Her symptoms persisted for about a week after the concussion.

Low sodium after head trauma, subarachnoid hemorrhage or brain tumor surgery can cause either SIADH or cerebral salt wasting syndrome. SIADH requires euvolemia and in cerebral salt wasting hypovolemia is present.  Because of these differences the treatments differ.  SIADH is treated by fluid restriction and cerebral salt wasting is treated by normal saline and salt tablets.  There is currently debate as to whether these are on the same spectrum with CSW involving dehydration.  Both have  hyponatremia, elevated urine sodium and concentrated urine.

FUN FACTS

1.       The literature also reports the BNP is elevated in cerebral salt wasting and not in SIADH.

2.       SIADH cannot be diagnosed if there is adrenal or thyroid dysfunction.

3.       Symptoms of cerebral salt wasting can last for months.

The European guidelines for treatment of hyponatremia in the seizing patient are simple. ( there is only one randomized study)

1.       Give 150 ml of 3% hypertonic saline over 20 minutes

2.       After the bolus recheck the serum sodium and give another 150 ml of 3% without waiting for the repeat sodium to result; so a total of 300 ml

3.       The goal is to raise the sodium 5 mmol/L.  Additional 150 ml boluses of 3% should be given until the sodium hits that target. 

In the case of our patient the next step was to give volume for dehydration. The problem with giving 3% hypertonic saline is two fold: you must monitor for hypokalemia and you can over correct the sodium leading to osmotic demyelination syndrome (ODS) and severe CNS deficits. The take home point is to go slow with your correction.

remember the bnp may help make the diagnosis

Parandoush S, Abbasi Z, Mohammadi N, et al. Hyponatremia in traumatic brain injury patients: syndrome of inappropriate antidiuretic hormone (SIADH) vs cerebral salt wasting (CSW). J Inj Violence Res. 2012Nov;4(3supple 1):17.

Fukuoka T, Tsurumi Y, Tsurumi A. Case Report Open access volume 2017 Article ID 8692017 https://doi.org/10.1155/2017/8692017

Nelson P, Seif S, Maroon J, Robinson A.  Hyponatremia in intracranial disease: perhaps not the syndrome of inappropriate secretion of antidiuretic hormone(SIADH). Journal of Neurosurgeyr 1981 dec ;55((6):938-41.  Doi: 10.3171/jns. 1981.55.6.0938.

Posted on March 15, 2018 by AJKDblog in NephMadness // 3 Comments  the chart of  the difference between SIADH and CSW appeared in the official blog of the American Journal of Kidney Diseases.