I would check in with a doctor about that shock when you bend your neck and about the muscle jerks. You could google l'hermitte's sign, or just ask your doctor. My experience is that neurologists hear a lot about skin sensations from people with a wide variety of diseases. They are tough to live with but not particularly helpful to the doctor in figuring out what is going on.
I would go back, to make an official record of your symptoms that may be helpful to you either now or later as things develop.