Please see the above link/pdf, page 47, if you have confusion regarding driving and Chiari/surgery in the UK. I had decompression surgery in January and was completely confused as to whether I had to medically surrender my driving license or not. Long story short, on the advice of the DVLA, I surrendered it. Mistake. If I’d found this document in January it would have saved me heaps of trouble. I still haven’t got my license back (not helped by lockdown unfortunatey).
You may have to consider other associated conditions (ie hydrocephalus, shunts) which are also in this booklet.
Hope this helps someone!