"Experimental studies have identified metabolic dysfunction as the key  postconcussion physiologic event that produces and maintains this state of vulnerability. This period of enhanced vulnerability is characterized by both an increase in the demand for glucose (fuel) and an inexplicable reduction in cerebral blood flow (fuel delivery).58 The result is an inability of the neurovascular system to respond to increasing demands for energy to reestablish its normal chemical and ionic environments. This is dangerous because these altered environments can kill brain cells." -- 
The American Orthopaedic Society for Sports Medicine - url: http://www.intelli.com/vhosts/aossm-isite/html/main.cgi?sub=151

     Moderate and Minor Head Injuries. Most brain injuries result from moderate and minor head injuries. Such injuries usually result from a non-penetrating blow to the head, and/or a violent shaking of the head. As luck would have it many individuals sustain such head injuries without any apparent consequences. However, for many others, such injuries result in lifelong disabling impairments. 

   Mechanism of Injury.  The brain is somewhat mobile within the spiny interior of the skull. Under normal circumstances the delicate brain is protected from contact with the spiny contours of the skull. This protective barrier is known as cerebrospinal fluid. It surrounds the brain, and under normal circumstances, cushions the brain from contact with its hard, spiny shell. 

    However, when the head is subjected to violent forces, such as those exerted in: automobile accidents;  violent shaking or whiplash;  forceful falls and blows; the brain may sustain permanent damage. Such damage results from the delicate brain being forcibly rotated and battered within the spiny skull, also known as, the brain vault. During such episodes brain tissue is ripped, torn, stretched, battered and bruised.  Such battering is followed by bleeding, swelling and bruising of brain tissue.  Sometimes the brain can recover from such insults without any apparent consequences.  In other cases the resultant difficulties can last a lifetime. 

     Brain Damage. Such damage, which results in functional impairments, can substantially interfere with the ability to return to a normal lifestyle. They are known as functional impairments because they interfere with the ability to perform basic functions such as walking and talking, thinking and knowing remembering and understanding. For example, memory, mood and fatigue top the list of the many on-going impairments that are caused by brain damage. Even a minor brain injury can have substantial, lifelong consequences. 

    Substantial Lifelong Consequences. After brain injury, things that once were easy and familiar become strange and difficult. Intensive mental effort is usually required to do things that required little or no effort before brain injury. Work and school, personal and family life often suffer too. Typically, children become unmanageable, grades drop, personalities change and they regress to a earlier  developmental stage.

     In adults, deadlines are missed, jobs are lost, savings dwindle and nerves fray. Behavior regresses and becomes upredictable, unreliable, frequently inappropriate, and sometimes violent,  role reversals are common.  While only one family member may have sustained a brain injury the entire family suffers from its massive intrusion.

     Scope of the Problem. Each year an estimated 5 million persons in the United States sustain head injuries. Of that number, 2 million Americans sustain head injuries that result in permanent impairments. Many such injuries do not even require a stay in the hospital, yet they result in impairments so profound that lives are forever changed.

    Recognizing the Problem. Often, the effects of minor to moderate brain injuries are not immediately apparent. Many months may go by before brain injury changes become apparent. Even then, special training and expertise are required to properly diagnose such impairments. Such fields of specialization are known as Neuropsychology and Neuropsychiatry. 

   Recognizing such problems is made even more difficult by perceptual and expressive impairments caused by brain injury. Brain injury causes diminished self-awareness and interferes with the ability to recognize changes in the self. It also causes mental confusion and a sense of uncertainty about experiences. Difficulties finding familiar words to communicate thoughts and desires hinders communication and fuels frustration. Many individuals do not report such symptoms out of fear of being thought of as mentally unsound. Others are shamed by such symptoms in themselves.

     Additionally, the very nature of brain injury interferes with the ability to recognize the problem. Frequently, brain injury causes memory impairments and expressive disorders. In real terms, this means that even when the memory survives the words might become elusive. Such impairments can hamper the ability to provide the doctor an accurate symptom picture. 

     Even minor head injury, also known as concussion, can cause substantial difficulties or impairments that can last a lifetime. Whiplash too, can result in the same difficulties as head injury. Such impairments can be helped by rehabilitation, however many individuals are released from treatment without referrals to brain injury rehabilitation, or guidance of any sort.