Nerve compression leading to severe pain and loss of nerve function
Out of all the nerve entrapment conditions, this is the one you really don’t want. Radicular symptoms are a combination of shooting pain, paraesthesiae (tingles / numb areas), and muscle weakness. The nerve itself is effectively dying because the compression (usually a nasty intervertebral disc bulge) is cutting off the blood supply to the nerve as well as its own internal fluid dynamics. The electrical signals that flow through the nerve cannot work in this state, and so you get loads of downstream effects in addition to just arm or leg pain.
The most obvious test for this that people may be familiar with is the reflex hammer. Normally if you strike a tendon the muscle will jerk suddenly, but with radiculopathy present, you will get less or even no response at all. Because of the seriousness of this situation (nerve damage can become permanent) we usually insist patients see a GP / neurologist or neurosurgeon for an opinion.
We still do the usual nerve entrapment type treatments for these cases, like releasing tight tissues in and around the nerves, and mobilising the spine. In some cases, recovery does occur, and reflexes do return, but for many of these cases – surgical release of the source of the entrapment is necessary.