hi a misalignment of the vertebra at the juncture of the spine and skull putting pressure on the spinal cord , thus giving you the symptoms in your body extremity's kind of like whip lash but being caused by slight jolts, I dont hold much with chiropractors there are some good ones but its a bit hit and miss if you find one, so best to see a doctor first, I put my neck out once and a friend who is a chiropractor sorted it for me he had a degree in physiology and was a trained radiologist, thats the only type of person I would let loose on my spine
but this is just a thought