What Is Dementia?


Dementia is not a specific disease but an umbrella term for many brain illnesses. Dementia includes a wide range of symptoms caused by neurodegeneration (degeneration of the building blocks of the brain). Neurodegeneration is a progressive deterioration of the brain that leads symptoms to get worse over time and provokes the appearance of new symptoms as the deterioration spreads. The symptoms include memory deficit, changes in behaviour and the inability to perform everyday activities.

The most important thing to remember is that, unfortunately, dementia is not a “one size fits all” disorder. Indeed, the exact symptoms experienced by a person can be different between individuals and the progression and speed of progression may differ from one patient to another. However, there is a general progression according to the type of dementia. This progression depends on the areas of the brain being gradually damaged.

Mixed Dementia

Mixed Dementia is the coexistence of multiple types of dementia at the same time. It is believed that the pairing of two types of dementia may have a considerable impact on the brain, greater than either type by itself. Mixed dementia is difficult to diagnose because the symptoms may greatly vary according to which type of dementias are combined. It is now believed that over 50% of people with Alzheimer’s disease have a coexisting pathology and that, most commonly, that second pathology is Vascular Dementia.

Alzheimer’s Disease

Alzheimer’s Disease is the most common type of dementia, but it is now believed that over 50% of people with Alzheimer’s Disease have a coexisting pathology. Alzheimer’s Disease is the most studied dementia. This disease is mainly characterized by two principal hallmarks: amyloid plaques and neurofibrillary tangles. Both come from the pathological aggregation of a different protein. The amyloid plaques are deposits outside the brain cells that have a toxic effect. The neurofibrillary tangles aggregate inside the cells and lead to brain cell dysfunction. The earliest symptom is usually short-term memory loss followed by reading problems, poor object recognition, poor sense of direction.

Vascular Dementia

Vascular Dementia is the second most common cause of dementia and is often combined with Alzheimer’s Disease. Vascular Dementia can occur after a stroke when blood flow is cut off from a part of the brain. This leads to brain cells being deprived of oxygen. The brain is the organ that consumes the most oxygen to operate, using up to 20% of total oxygen consumption. Therefore, the brain is particularly susceptible to this type of injury. Strokes can have a cumulative effect. The symptoms vary from person to person because the symptoms depend on the area of the brain that was damaged. The symptoms also vary according to the extent of the damage (small or large stroke).

Lewy Body Dementia

Lewy Body Dementia is often misdiagnosed either as Parkinson’s Disease or Alzheimer’s Disease. Lewy Body Dementia is a complex progressive disease. It usually presents with symptoms that are commonly seen in Parkinson’s Disease or Alzheimer’s Disease leading to its misdiagnosis and unfortunately leading to less than ideal management. The hallmark of Lewy Body Dementia is deposits inside the cell (called alpha-synuclein neuronal inclusions) that are accompanied by neurodegeneration (degeneration of the building blocks of the brain). The main symptoms include memory loss, disorientation, visual hallucinations and sleep issues.


Parkinson’s Disease Dementia

Parkinson’s Disease is a long-term neurodegenerative disease that mainly affects the motor system by depleting a region in the basal ganglia of dopamine. It is thought that the prevalence of cognitive impairment in Parkinson’s Disease is roughly around 30%. However, as the disease progresses, it is estimated that up to 80% of patients will develop Parkinson’s Disease Dementia. The key brain changes leading to dementia are Lewy Body deposits (called alpha-synuclein neuronal inclusions), the same seen in Lewy Body Dementia. Parkinson’s Disease Dementia patients have an existing diagnosis of Parkinson’s Disease before being diagnosed with dementia whereas Lewy Body Dementia patients typically have dementia symptoms before motor symptoms. The main cognitive symptoms of Parkinson’s Disease Dementia are reasoning and judgment, irritability, paranoia, depression and speech impediments.

Frontotemporal Dementia

Frontotemporal Dementia is a term for a group of rare disorders affecting the frontal and temporal lobes of the brain. Frontotemporal Dementia tends to occur at a younger age than other types of dementia. A higher amount (compared to other types of dementia) of Frontotemporal Dementia is familial, meaning that it is associated with a mutation of a gene that can be passed from parent to child. Frontotemporal Dementia also tends to be more rapidly progressing than other types of dementia. The main functions affected by Frontotemporal Dementia are language skills, the inability to focus and the inability to control impulses.

Other Types of Dementia

There are many other types of dementia. Here is a non-exhaustive list of other types of dementia

  • Creutzfeldt-Jakob Disease
  • Normal Pressure Hydrocephalus
  • Chronic Traumatic Encephalopathy
  • Traumatic Brain Injury
  • Down Syndrome
  • Posterior Cortical Atrophy
  • Wernicke-Korsakoff Syndrome
  • Huntington’s Disease
  • HIV-Related Cognitive Impairment or HIV-Associated Neurocognitive Disorder

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