Most GPs and specialist consultants can't distinguish whether mTBI symptoms are neurological, physiological or psychological following a clear CT scan. These are cyclic domains and act on each other.
Whiplash and impact injuries damage the neck, face and head. Nerves in the cervical spine get impinged and tissue damage causes inflammation that compress nerves, both cause tremors in the body and affect signalling to the vestibular system and facial muscles causing balance and visual issues.
The vestibular system comprises fluid filled canals in the inner ear and temperomandibular (jaw) joint. There are crystals in the canals that trigger motion sensors. Following an injury these crystals get displaced and no longer trigger the motion sensors properly, causing confusion in body stability. The vestibular system is also linked to motor control in the eyes which lose horizontal and vertical axis control.
Eyes and eye regions also get damaged in accidents affecting muscles that control movement and eye components such as the retina that affects sensory signalling to the brain.
All the sensory signals go to the thalamus, which is a junction box in the brain. If the signals are not normal, the thalamus triggers a stress response that increases cortisol, blood pressure and flow, increases breathing, and affects the gastric system by increasing acid production. This response is automatic, pre-perceptual, pre-congitive, ie you haven't thought about it, it's not psychological or of the mind.
This stress response that acts within 100 milliseconds and within 200 milliseconds it triggers a change in mood (this all occurs in the right brain hemisphere). The left brain hemisphere is triggered via signals across the corpus collosum and initiates an emotional response followed by language based thoughts, objective reasoning, (what the fuck is going on!) within 300 milliseconds. This is the psychological element. (Visual based 'thoughts' are linked to PTSD in the right hemisphere). If the events that trigger the stress response continue the effects become hard wired in the brain.
None of what I have described so far is due to neurological damage. They are psychosomatic and psychological.
If a CT brain scan is clear then what I have described are the symptoms seen by GPs and consultants.
If you have visual, vestibular treatment many of the causes of the stress response can be solved and remaining psychological effects can be overcome.
Only after this, if symptoms persist, a neurological condition can be investigated.
The problem is that most health authorities in the UK have no, or inadequate visual and vestibular services. Which means the causation of stress response continues and the psychological effects persist resulting in depression. The psychological effects can't be solved until the causation is treated. The neurological effects of brain damage are hardly ever found.
New brain imaging techniques, diffusion tensor imaging, can identify neurological damage traumatic axonal injury, after an accident, but this imaging technology is not available in mainstream healthcare hospitals.
So until there are proper vision and vestibular screening and treatments and also modern imaging technology, particular types of brain injury, the most common, mTBI/PCS will not be dealt with.
Hopefully the ABI Bill will change the system.