Frequent Drop In Sodium Levels Causing Confusion, Imbalance, Has Fluctuating BP. Any Ideas?

My Mother has been in the E.R six times in the past five months with low sodium , 3 of witch turned into hostpital stays, she is in the hostpital now, S nt V s Portland Oregon. Her lowest level wae 106. When her sodium drops she becomes confused and sometimes has falls. My mother is 76 years old has had many mini strokes over the past six months. we have been to two different hostpitals, they have run the normal tests and procedurs and cannot find an answer. I will say Sn t V s is lookiing deeper into the possibilites witch is nice.I would like to know of any rare cases of elderly haveing crazy drops in their sodium levels that are not easely explained. Her blood pressure sometimes goes crazy off the charts, uncontrolable even with medication changes, and when her sodium drops she falls when she gets up from bed,but not rite away, after she has been up for a couple of min. My Mother is at her witts end this is very difficult for her. Something is being overlooked, please any ideas or past cases would be so much appreciated. Thank you Corey Thelin