My tri girl developed Chiari around the age of 3- it was never severe but very annoying to her with scratching, which she'll still do but much less). She responds pretty well to pregabalin and omeprazole (which somehow decreases the CSF pressure)- the omeprazole I only really give when it rains or is very damp (or sudden change in barometric pressure)- which all worsen her symptoms significantly. She now is able to walk with her harness and have better quality of life. She has been on the meds for about 3 years with no problems- only, interestingly God forbid I run out of meds, she gets significantly worse even than when before I started her on it. I don't think it's because the chiari itself is worse b/c I'm not using higher doses to maintain her comfortably. There may be some rebound effect of some sort I'm not thrilled about. Blood chemistries should be followed once a year (I do twice).
She was initially started on gabapentin (which is Neurontin) which did nothing for her. The pregabalin (Lyrica which is expensive and doesn't come in generic) has to be compounded by a pharmacy I use in Arizona (Diamondback Drugs)-- I once ran out of meds because they now require to have a hard copy prescription mailed (not faxed) and then they will ship it. They will NOT mail it otherwise. I was so upset I wasn't mailed a notice of this new law of pregabalin being a "triplicate" Rx. So I had my vet give me a Rx for a few pills of Lyrica, which thankfully my insurance Trupanion covered 90%.
Just wanted to share this info as it has made a big difference with my Bella and with no worsening of symptoms whatsoever.