I also sustained my TBI in a car accident. Like you, my muscles seem to have their own agenda. For example, my hand will fly open (usually when I'm holding something hot or fragile), I get terrible spasms, my hands shake and I have various facial ticks.

As Mark said, these problems stem mostly from nerve damage in my neck from whiplash. After an MVA, stabilizing the neck, through good posture, pt and, if necessary/possible, surgical intervention, is very important.

A simple home test for neck instability is to put on a cervical collar and see if your symptoms improve. As it was deemed too risky to operate on my neck, when I'm having a really bad day, my PT still has me "collar up." Among other things, my headaches get less severe.

In the interim, you might want to consider icing the back of your neck to get some relief.

Welcome to NT.