Woke Up In Middle Of The Night Sleeping On My
Peripheral nerve compression
Detailed Answer:
Hello, I'm Dr. Branch, thanks for using Ask a Doctor. As long as you were able to move your arm and wrist without any problems, and you don't have any other associated symptoms such as slurred speech or leg weakness on the left side, I would suspect that you have a temporary nerve damage from compression on your left arm. This does commonly affect the finger flexors and extensors as you've described, and may have affected both see radial and ulnar nerves. Especially for the radial nerve, this commonly occurs when sleeping on the arm, and has been called Saturday Night Palsy because this often happens when people are intoxicated and sleep on their arm without knowing it. The ulnar nerve is often also affected, as it sounds like in your case.
Recovery may take several days to weeks, but generally you should recover from this completely. If you are still having any weakness or symptoms after several weeks, I would suggest getting this evaluated to see if there is permanent damage or some other cause.
I hope that helps and makes sense, please let me know if you have any other questions about any of that and I would be glad to discuss it with you further.