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More ‘severe’ TBI is a well-established risk factor for a variety of neurodegenerative diseases including Alzheimer's and Parkinson's disease. Recently, large epidemiological studies have additionally identified mTBI as a risk factor for dementia. Repetitive mTBI and repetitive sub-concussive head trauma have been linked to increased risk for a variety of neurodegenerative diseases including chronic traumatic encephalopathy (CTE). Robust studies have been limited by several factors. Mainly incorrect diagnosis, agreement on what CTE is, etc. The prevalence of CTE is unknown and the amount of mTBI or sub-concussive trauma exposure necessary to produce CTE is unclear.1.
Neurodegenerative Disease (NDD), is an umbrella term for a range of conditions which primarily affect the neurons in the human brain.
Neurons are the building blocks of the nervous system which includes the brain and spinal cord. Neurons normally don’t reproduce or replace themselves, so when they become damaged or die they cannot be replaced by the body.
NDD are incurable and debilitating conditions that result in progressive degeneration and/or death of nerve cells. This causes problems with movement (ataxias), or mental functioning (dementias).
Dementias are responsible for the greatest burden of neurodegenerative diseases, with Alzheimer’s representing approximately 60-70% of dementia cases.
Common NDD are:
Alzheimer’s disease (AD) and other dementias
Parkinson’s disease (PD) and PD-related disorders
Motor neurone diseases (MND)
Huntington’s disease (HD)2.
Alzheimer’s disease (AD), is the most common form of dementia, affecting up to 70% of all people with dementia. It was first recorded in 1907 by Dr Alois Alzheimer. Dr Alzheimer reported the case of Auguste Deter, a middle-aged woman with dementia and specific changes in her brain. For the next 60 years AD was considered a rare condition that affected people under the age of 65. It was not until the 1970s that Dr Robert Katzman declared (rather boldly at the time) that "senile dementia" and AD were the same condition and that neither were a normal part of ageing.
AD can be either sporadic or familial.
Sporadic AD can affect adults at any age, but usually occurs after age 65 and is the most common form of AD.
Familial AD is a very rare genetic condition, caused by a mutation in one of several genes. The presence of mutated genes means that the person will eventually develop AD, usually in their 40's or 50's.3.
There is no specific laboratory blood test or the like for AD. Evidence can generally only be found at autopsy.
Parkinson’s Diseases (PD), is a progressive neurological condition that affects people from all walks of life. It is quite common, with approximately figures ranging from tens to hundreds of thousands in the developed world living with PD.
The average age of diagnosis is 65 years, however younger people can be diagnosed with PD too. This is referred to as Young Onset Parkinson’s.
It is not easy to diagnose PD. There are no laboratory tests (such as a blood test or brain scan), so it is important that the diagnosis is made by a specialist, such as a neurologist. The specialist will examine for any physical signs of PD and take a detailed history of symptoms.4.
The race is therefore on to find a more specific indicator which will not only assist with diagnosis but maybe prevent or slow down progress if relevant treatment can be provided.
Chronic Traumatic Encephalopathy (CTE)
Technically it is described as a progressive neurodegenerative disease (tauopathy) caused by total brain trauma. However, it is not limited to athletes who have reported concussions. As such, the incidence and prevalence is unknown.
Unfortunately current technology and know how also CTE to be diagnosed only after death by distinctive reactive stains of the brain for Tau protein. It is not the same disease as Alzheimer’s.
Typical signs and symptoms include a decline of recent memory and executive function, mood and behavioural disturbances (especially depression, impulsivity, aggressiveness, anger, irritability, suicidal behaviour and eventual progression to dementia). However, the initial signs and symptoms do not typically manifest until decades after the trauma was received (ages 40-50).9.
At this stage, the jury is still deemed to be out re the clear association between serial mTBI and CTE. Although, evidence continues to mount. Until cause and effect is proven in living subjects via a specific biomarker(s), imaging or other such testing, it is argued that caution should be the norm and that ALL concussions should be diagnosed and treated correctly.
Growing evidence of undiagnosed/treated mTBI leading to chronic neurological conditions.