Traumatic Brain Injury – Memory Loss Through Brain Damage

What is Traumatic Brain Injury?

TBI is the acronym for traumatic brain injury.  This covers any brain damage caused by an accident or injury as opposed to damage from a disease or birth and in many cases is avoidable by taking appropriate precautions.  The most commonly recognised causes of traumatic brain injury are vehicle accidents, sporting injuries and military incidents.  Traumatic brain injury is also caused by falls in young children and the elderly, in fact the main age groups affected by TBI are 0-4 and then over 65!  It is just that injuries in these age groups do not receive much publicity in the media unless they are related to child abuse cases or crimes and so are under-reported.  

What Causes TBI?

Before seat belts became mandatory the main injuries in car accidents were crush injuries from being thrown against the steering wheel and injuries caused by being thrown through the windscreen or from the vehicle. These days we strap up and modern cars have neck supports designed to prevent whiplash.  TBI, however, can be caused by the brain being violently jolted inside the skull on impact even though the body itself is immobilised so while crush injuries have diminished, the number of brain injuries is still high.  

This kind of brain jolt causes a phenomenon called coup and contrecoup injuries in which the brain is bruised both front and back as it bounces to and fro in the skull and may not be immediately obvious as it is unlikely that there will be obvious skull damage.  This is also the cause of brain injury in babies and small children who are shaken (shaken infant syndrome). This can be potentially fatal or cause permanent brain damage leading to seizures and cognitive or developmental problems.  

The Dangers of Brain Swelling

When the brain is injured, like any other body part, it swells.  Unfortunately, however, the skull is not elastic and there is no where for the swelling to expand so it compresses the adjoining areas of the brain and can cause permanent and severe damage or even death unless the pressure is promptly relieved surgically.

 In some ways the prognosis for a fractured skull is sometimes better than that for a closed skull injury as there is room for the swollen brain to expand through the fracture, reducing pressure on other parts of the brain and the brain stem and also lessening scar tissue caused by swelling pressing against the ridges of bone in the skull.  This is why anyone with a suspected brain injury is kept under observation, even if they initially seem fine after the incident, as brain bleeding and swelling may only manifest themselves later, through vomiting, sleepiness or coma, fully dilated (blown) pupils and severe headache.  

The Effects of TBI

The effects of TBI vary considerably depending on which part of the brain has been affected and the severity of the injury. For instance damage to the front of brain (frontal lobes) can cause mood changes such as depression, anxiety, apathy and behavioural problems such as aggression and loss of inhibitions.  In veterans frontal lobe damage can be compounded by PTSD and it can be difficult to distinguish between the impact of physical brain damage and psychological damage from extreme emotional experiences.  

Interestingly, in post mortem examination of the brain tissue of war veterans exposed to big explosions, researchers have now observed minute pinhead sized scars so tiny that they don’t show under normal scans so perhaps the World War One term ‘shell shock’ was more accurate than first thought.  These tiny scars may be responsible for symptoms that were previously considered to be psychological rather than physiological.

Dangerous Games

Another significant cause of brain damage is the sporting arena.  While we have been long aware of the brain damage associated with boxing, hence the term ‘punch drunk’, this is not the only sport that is hazardous.  American football has been in the limelight recently, as has cricket, and it is now realised that while helmets may protect against possible fractures and impact injuries, they are little defence against concussion and the coup/contrecoup damage referred to above, where the brain actually ricochets inside the skull on impact.  Brain bleeds and other damage may still arise and helmets may give a false sense of security.  

Elderly at Risk

Elderly people are vulnerable to TBI for a range of reasons and sometimes cause and effect are unclear.  Dizziness and impaired balance, cardio-vascular problems, poor vision, dementia – these can all cause falls but may also be caused or aggravated by falls. This is why when an elderly person is admitted to hospital after a fall it is important that someone who knows them well is there to advocate for them and defines what their normal condition actually is.

The Impact on Memory

No matter what the cause of the TBI, memory may be affected, either temporarily or permanently.  Whether it is retrograde or anterograde amnesia or a combination of both depends considerably on the nature and extent of the injury.  Retrograde amnesia is the loss of memories of past events.  This may just be the events immediately preceding and during the event that caused the injury but may also go back further.  Anterograde amnesia is loss of the ability to make new memories.  In very rare cases this can be extreme and make normal independent life impossible but for most people with TBI memory function does recover with time and there are various work-arounds that can be deployed to circumvent any short-comings.  Amnesia will be covered in greater detail in a separate article.

 

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