Just lost a bunch of typing. Yuck.
I've got two answers for you, one to your explicit question, and one to your implied question.
I, too, have minor symptoms for the most part. I don't do much for the brain-fog feeling. Sometimes I take Tylenol if it feels like a headache, sometimes I rest, sometimes I take a walk or an easy swim to see if that helps. Mostly I just wait it out.
Your bigger question seems to be how do I figure out if I need surgery if my symptoms aren't bad. I wanted to share my thought process, and also to recommend a test which certainly helped me figure things out a bit better.
I, too, have tingling in my hand as one of my minor symptoms. (I get some vague headaches, some dizziness these days, and recently some bad leg cramps.) One NS ordered an EMG (electro myleogram???) for me to investigate the tingling. There are a lot of reasons for tingling, and some is probably normal and age-related. He wanted to eliminate other possible problems so he didn't do an unnecessary surgery.
An EMG and a related test basically measure the speed at which signals travel along your peripheral nerves. There are two tests, one with little pads on your skin, and one with little needles like acupuncture needles. (Yes, it feels a bit icky, but only one needle actually made me wince. The peace of mind for me made it totally worth it.) The doctor and a technician use pairs of pads or needles, and a tape measure to check the exact distance between the two points. They know how long it is supposed to take for the signals to travel a given distance, and a range for normal results, and they have two sides of the body to compare. They can also test to see if your tingling is caused by something pinching a nerve lower down (like a tennis elbow) as opposed to a problem which starts in the spinal cord.
In my case, my tingling was pretty benign. But my test results were not. They showed that the problem was originating in my spinal cord. My MRI showed that my disks couldn't be causing the problem (the same symptoms and damage can result from a herniated or degraded disk). The EMG also showed cumulative damage to my nerves. The doctor told me the syrinx had been damaging my nerves for at LEAST five YEARS, and probably more like a decade. It also showed that in my left leg, where symptoms aren't as noticeable as my left arm, I am still in the normal range, but far below the nerve activity in my right leg.
This made the picture very clear for me. The syrinx wasn't new, and it wasn't a minor issue. It had been messing with my body for a long, long time.
Thus, I've decided to have surgery (on Monday, actually).
It seemed to me, for me, that the question was always "is my Chiari actually symptomatic?", not "are my symptoms something I can deal with?" For me, but not for everyone, once I understood that it is really, measurably symptomatic, that there is no possibility I am imagining or psychosomatically creating these symptoms, I wanted it treated. I know for sure I don't want this to progress, and it is my understanding that there is always progression, albeit sometimes very slow worsening of symptoms.
I don't think everyone needs an EMG, and I don't think everyone needs to wait for measurable nerve tests. But for me, with more minor symptoms (at least until the last few weeks), I found the decision to proceed with surgery much easier knowing I had this measurable result.
I hope this helps! Good luck to you, and to the rest of the crew, who suffers so much with this condition.