By medical definition, whiplash is an injury whereupon the injured person that is in a motor vehicle is rear-ended by another motor vehicle. This creates the anatomic phenomenon of hyperextension (the neck bends excessively backwards, followed by hyperflexion (the neck bends forward-chin to chest). With the backward compressive forces, the facet joints, disc and nerve roots can get injured. With the hyperflexion portion of the injury, muscles and ligaments often get stretched beyond their normal anatomic limit and therefore injured.
The two most common complaints following a whiplash injury include neck pain and headaches. Often the headaches are in the back of the head. This is sometimes due to a medical condition known as occipital neuralgia. An injury to the nerve at the top of the neck/base of the head gets injured from the whiplash mechanism of injury and causes pain in the occiput (back) of the head. One does not need to strike his or her head to suffer from a post-traumatic headache syndrome. The intensity and frequency of post-traumatic headaches usually decreases with time.
Ninety percent of persons suffering from a whiplash injury do make a full recovery. Persons with whiplash-related pain beyond one year of the accident are considered to have suffered permanent injuries.
Within the category of whiplash there is the subcategory of a minimal impact soft tissue (MIST) injury. There is some research, as well as our clinical experience, indicating that if the worst pain is the day after the motor vehicle accident, such symptoms are very limited, most often in the order of days. Another way to look at this is that if a disc herniation occurred or if a bone was broken or dislocated, for those more serious injuries, the worst pain is going to be at the time of impact. With a strain injury, some delayed response development of inflammation could make the pain worse the next day.