Hi, there can be several reasons....many of us with Chiari also have a related condition Ehlers-Danlos...which is a connective tissue disorder.....since the tissues are not holding our joints together like they should, our muscles work over time trying to hold us in place which can put strain on the muscles causing fatigue and pain and even tremors in the muscles.
With EDS another common issue for those with Chiari is Cervical Cranial Instability...and with a bumpy car ride ur head bobbles all over putting strain on the brain stem and spinal cord.
For me b4 surgery and even for a time post op, I did not attempt a long car ride without a pillow to help hold me held stable....I tried a neck pillow....not a big help, but using a big fluffy bed pillow worked great, I would sit in the front passenger seat with it reclined just enuff so with the pillow I was still sitting upright.
So to answer ur question....yup...after a long car ride and I was driving, I felt ok...but suffered a drop attack...which I incurred injuries which required surgery...2....so yeah, a car ride can do a lot.
Does it tend to be temporary or more long-term in the effects?
For me it all depended on the ride and what else I may have done the day b4 or even after the ride, it could last a few days....but was a more temp issue.
Long term, it could have an effect pre op, but once I had surgery it was a temp issue that I do not really get now, I do not even use the pillow nemore.