Why are both my arms suddenly so heavy and weak?

[Greenb2]

This evening I experienced such an overwhelming sensation of heaviness in both arms that all I could do was drop them to my sides. I had just come from the pet store and had carried a big box of cat litter. When I sat down to start the car, I could only sit and wait for my arms to come back to a minimum level of strength. After driving home, I went online to find out what had just happened. With some residual weakness and great difficulty typing keywords, I found this website. I am relieved to see others have experienced similar symptoms of unknown origin. I also have a history of TBI from a car accident almost 30 yrs ago. Btw I am an active, short, small-boned 65 y/o female, skinny and wirey my whole life. I am post menopausal and I had no significant pre-, peri- or menopausal signs. I do have a history of GERD, cervical disc degeneration at C4-C6 probably exacerbated by that MVA all those yrs ago. I have multiple joint damage sites from osteoarthritis and was on a fairly good regimen of meds for pain and inflammation management. I am currently in the process of getting pre-authorization by medical insurance for a CT scan for lower back for an epidural to deal with persistent sciatica and lower lumbar pain. I've completed physical therapy annually, for as many sessions as my insurance will allow for the past six years, which did in fact help strengthen my core lumbar area, but now I am experiencing sacral pain, and my sciatica persists, worse on left than right. This acute bilateral arm weakness is worrisome, and I'll certainly keep posting if I get a Dx.