Reflexes help to determine where the problem in the nervous system is located. Reflexes that are diminished support that there is a problem outside of the spinal cord in the periphery (like typically for GBS). Reflexes that are increased support that the problem is in the spinal cord or brain. I have really brisk reflexes–if someone taps my knee, watch out, but that has been the case all my life. However, it is a major reason the neurologists keep trying to make my neurologist problems be MS or breakdown of nerves or problems in the brain. Other times, he has argued that my reflexes might be “less brisk” than they used to be…..
FYI, it used to be one of the “criteria” that someone had GBS that they have reduced or absent reflexes. As people have appreciated the diversity in GBS/CIDP, this “criteria” has been dropped, but a lot of people still “believe” it. In reading about this at the beginning, it is worth knowing that when there is damage to the nerve cell (axonal damage) as opposed to damage to the lining/insulation of the nerve (myelin), one is more likely to have brisker (or less reduced) reflexes. But, lack of loss of reflexes does not mean that the damage is axonal, because the nervous system is complex.
WithHope for cure of these diseases

I am assuming that “brisk relflexes” would mean fast? I am not sure about that, but I don’t really think whether or not one has reflexes or not is important; other than in the early stages of being diagnosed. I got all of my reflexes back, even though I still have considerable weakness & must wear AFOs. Doctors like to feel important when checking for them, I think…