Hi and welcome to the Chiari forum.
I had surgery 10 years ago this May....and I am doing better.....and it can take time to see ALL the benefits due to related conditions you may have.
Having the right Dr is KEY !!
Have you had a CINE MRI? The numbness can be due to a related condition Syringomyelia....a syrinx(cyst) forms and fills with CSF and puts pressure on the nerves in the spinal cord which can cause numbness,,,,
Most times and which was the case for my surgery I had a CSF obstruction and had surgery to prevent a syrinx from forming....
You will also want the Dr to rule out ALL related conditions as they can affect the outcome of surgery.....if the Dr is not a true Chiari specialist ( but does the surgery) they will not check you for them and will also say they can fix or cure you....if you have a Dr tell you that RUN...there is no cure for Chiari as it is a malformation of the skull, but it can slow progression and lessen some symptoms.
Many of those that have gotten worse post op have had related conditions not found prior to surgery.
Educate yourself on Chiari, ALL related conditions and the Dr you choose to go to.