N.:
It sounds like your son is describing what medical professionals call "phantom pain". The cause does not show up with medical testing, but seems "real" to the person. Fibromyalgia and TN patients were originally diagnosed with this.
We had this experience, and an Upper Cervical doctor located the cause: the brain stem. We didn't know that 70 trillion nerves run from the brain to the body through the brain stem. Trauma, a fall, or birth trauma, can move the atlas bone and interrupt nerve communication at the brain stem level. This can create nerve spasms that cause painful spikes in any area of the body. (My husbands was in the face; another woman had them in her vaginal area, and another we met on top of her face. In the legs or feet are well documented.)
I don't know what state you are in, but there are 1760 UC DC's world-wide. Only Upper Cervical DC's are trained to take exact Xrays to see the position of the atlas and then precisely correct the bone. NO GUESSWORK! No popping or rotating of the neck! They train for 3-5 years after their doctorate to learn this science.
You can Google Upper Cervical Advocates and find a web site that has leads to a list of UC DC's on the Links page under the Blue Add'l sources.
Blessings! Hope this information helps solve your problem. After our 12 year battle with nerve pain we don't want to see anyone suffer again, and have thousands of stories form those who found their answer with Upper Cervical.
R. Tomasi
ps I forgot to tell you that you can sometimes "see" this problem. Lay him on his back and straighten out his legs. Is one leg shorter than the other? Stand him up and look at this ears, eyebrows and shoulders? Is one lower than the other? If Yes, his body is reacting to an atlas bone that is shifted and the spine is curving causing one leg (shoulder, eye, ear) to appear shorter than the other.
You can see this on many TV personalities! Or, friends and family. Just look! Posture checks don't lie, and they confirm this instead of the potassium deficiencies mentioned.