I am relieved that you have decided to post here too.

I am going to link to your thread, so others here can see my suggestions and responses.

Glyde's posts begin at post count #7.

http://neurotalk.psychcentral.com/thread194501.html

All of us here have slowly learned to become our own detectives.
Neurologists are quite limited and only work from their therapeutic books, some of which may be out of date, and are quite conservative given their high liability insurance rates.

Another option for you if you really want a DOCTOR ...would be a sports physician, preferrably one who helps with bicycle injuries.

Here is a link to diagrams of the nerves in the head.
http://www.netterimages.com/image/7274.htm
First off it would be helpful if you can point to exactly where you
get these spells of stabbing/itching/burning pain.

I've been thinking about you quite a bit, over the past few days.
I really think you had some compressive injury involving your helmet when you had your accident.
If some nerves were crushed, they wouldn't start immediately to fire erratically until they started to regrow back. Peripheral nerves do grow back and often send mixed up or useless signals as a result.

So I think you should keep a journal, with when these happen.
For example, only at night? when you wear hats or caps? Only after certain foods? Only after you shampoo? Only after you apply hair gels/creams?

I'd really stop the gels for now that you mentioned as they are high in alcohol, and alcohol irritates nerve endings big time.

There are dietary interventions we use here to quiet nerves. Supplements, and other things that may provide some comfort for you. Ice treatments do quiet firing quite a bit, whereas heat can stimulate pain firing. If your pain events are at night, with you applying pressure to your head on the pillows, then that would suggest, compression problems. There are cold caps that chemo patients wear to cool the head during chemotherapy. Some are less expensive than others. A simple gel ice pack may work as an
experiment.

If you are low in magnesium, like the 70% rest of the U.S., you can provide it orally or in a lotion topically to help antagonize the pain receptors. (they are called NMDA receptors). MSG in foods stimulate these pain receptors, so avoiding it is important.

Chronic application of steroids to the skin, change the composition of the skin and thin it, and may have accidentally iritated your nerve endings more.
The scalp is highly vascular and with lots of nerves in order to
nourish the hair follicles.

I myself use magnets for pain, at night, often. And if necessary I can guide you to inexpensive strong magnets to try. Magnets applied carefully block the flow of ions into nerve cells, much like lidocaine does. So then the pain signals are blocked off. I usually leave this for last, as other things often work most of the time for people. (I have a thread here on magnets).