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Types of Dementia

Dementia is a general term for loss of memory and other mental abilities severe enough to interfere with daily life. It is caused by physical changes in the brain. The words "Alzheimer's" and "Dementia" are often used interchangeably, but they are NOT the same. "Dementia" is a term that means a person is no longer able to function on their own because of a lasting impairment of multiple mental abilities affecting memory, attention, and reasoning. Dementia can be caused by many different medical conditions, such as a severe head injury or major stroke. Alzheimer's is the most common form. It accounts for approximately 60-80% of all dementia cases. Other common dementias are Lewy body dementia, Frontotemporal dementia, vascular dementia, and Parkinson's disease, and Huntington's Disease. Less common are Creutzfeldt-Jakob Disease, Wernicke-Korsakoff Syndrome, Normal Pressure Hydrocephalus or Mixed Dementias.

Alzheimer's disease

Alzheimer's disease is a progressive degenerative disease that attacks the brain and results in impaired memory, thinking, and behaviour. Alzheimer's is a disease of the brain that causes a steady decline in memory. As a form of dementia, Alzheimer's is the common type of dementia and accounts for an estimated 60 to 80 percent of cases. Alzheimer's disease is a progressive degenerative disease that attacks the brain and results in impaired memory, thinking, and behaviour.

The American Psychiatric Association's definition extends the definition further.

"The essential feature of the presence of dementia of insidious onset and gradual progressive course for which all other specific causes have been excluded by the history, physical examination, and laboratory tests. Dementia involves a multifaceted loss of intellectual abilities, such as memory, judgement, abstract thought, and higher cortical functions, and changes in personality and behaviour."

Symptoms:

Difficulty remembering names and recent events is often an early clinical symptom; apathy and depression are also often early symptoms. Later symptoms include impaired judgment, disorientation, confusion, behavior changes and difficulty speaking, swallowing and walking.
New criteria and guidelines for diagnosing Alzheimer's were published in 2011 recommending that Alzheimer's disease be considered a disease with three stages, beginning well before the development of symptoms.

Brain changes:

Hallmark abnormalities are deposits of the protein fragment beta-amyloid (plaques) and twisted strands of the protein tau (tangles) as well as evidence of nerve cell damage and death in the brain.

Vascular dementia

Previously known as multi-infarct or post-stroke dementia, vascular dementia is the second most common cause of dementia after Alzheimer's disease. Vascular dementia is a general term describing problems with reasoning, planning, judgment, memory and other thought processes caused by brain damage from impaired blood flow to your brain. You can develop vascular dementia after a stroke blocks an artery in your brain, but strokes don't always cause vascular dementia. Whether a stroke affects your thinking and reasoning depends on your stroke's severity and location. Vascular dementia also can result from other conditions that damage blood vessels and reduce circulation, depriving your brain of vital oxygen and nutrients.

Symptoms:

Impaired judgment or ability to plan steps needed to complete a task is more likely to be the initial symptom, as opposed to the memory loss often associated with the initial symptoms of Alzheimer's. Occurs because of brain injuries such as microscopic bleeding and blood vessel blockage. The location of the brain injury determines how the individual's thinking and physical functioning are affected.

Brain changes:

Brain imaging can often detect blood vessel problems implicated in vascular dementia. In the past, evidence for vascular dementia was used to exclude a diagnosis of Alzheimer's disease (and vice versa). That practice is no longer considered consistent with pathologic evidence, which shows that the brain changes of several types of dementia can be present simultaneously. When any two or more types of dementia are present at the same time, the individual is considered to have "mixed dementia" (see entry below).

Dementia with Lewy bodies (DLB)

Dementia with Lewy bodies (DLB) is a type of progressive dementia that leads to a decline in thinking, reasoning and independent function because of abnormal microscopic deposits that damage brain cells over time.

Symptoms:

People with dementia with Lewy bodies often have memory loss and thinking problems common in Alzheimer's, but are more likely than people with Alzheimer's to have initial or early symptoms such as sleep disturbances, well-formed visual hallucinations, and muscle rigidity or other parkinsonian movement features.

Brain changes:

Lewy bodies are abnormal aggregations (or clumps) of the protein alpha-synuclein. When they develop in a part of the brain called the cortex, dementia can result. Alpha-synuclein also aggregates in the brains of people with Parkinson's disease, but the aggregates may appear in a pattern that is different from dementia with Lewy bodies.

The brain changes of dementia with Lewy bodies alone can cause dementia, or they can be present at the same time as the brain changes of Alzheimer's disease and/or vascular dementia, with each abnormality contributing to the development of dementia. When this happens, the individual is said to have "mixed dementia."

Mixed Dementia

In mixed dementia abnormalities linked to more than one type of dementia occur simultaneously in the brain. Recent studies suggest that mixed dementia is more common than previously thought.

Brain changes:

Characterized by the hallmark abnormalities of more than one type of dementia —most commonly, Alzheimer's and vascular dementia, but also other types, such as dementia with Lewy bodies.

 

 

Parkinson's disease

Parkinson's disease is a progressive disorder of the nervous system that affects your movement. It develops gradually, Sometimes starting with a barely noticeable tremor in just one hand. But while a tremor may be the most well-known sign of Parkinson's disease, the disorder also commonly causes stiffness or slowing of movement.

In the early stages of Parkinson's disease, your face may show little or no expression or your arms may not swing when you walk. Your speech may become soft or slurred. Parkinson's disease symptoms worsen as your condition progresses over time.

Although Parkinson's disease can't be cured, medications may markedly improve your symptoms. As Parkinson's disease progresses, it often results in a progressive dementia similar to dementia with Lewy bodies or Alzheimer's.

Symptoms:

Problems with movement are a common symptom early in the disease. If dementia develops, symptoms are often similar to dementia with Lewy bodies.

Brain changes:

Alpha-synuclein clumps are likely to begin in an area deep in the brain called the substantia nigra. These clumps are thought to cause degeneration of the nerve cells that produce dopamine.

Frontotemporal Dementia

Includes dementias such as behavioral variant FTD (bvFTD), primary progressive aphasia, Pick's disease and progressive supranuclear palsy.

Symptoms:

Typical symptoms include changes in personality and behavior and difficulty with language. Nerve cells in the front and side regions of the brain are especially affected.

Brain changes:

No distinguishing microscopic abnormality is linked to all cases. People with FTD generally develop symptoms at a younger age (at about age 60) and survive for fewer years than those with Alzheimer's.

Creutzfeldt-Jakob Disease

CJD is the most common human form of a group of rare, fatal brain disorders affecting people and certain other mammals. Variant CJD (“mad cow disease”) occurs in cattle, and has been transmitted to people under certain circumstances.

Symptoms:

Rapidly fatal disorder that impairs memory and coordination and causes behavior changes.

Brain changes:

Results from misfolded prion protein that causes a "domino effect" in which prion protein throughout the brain misfolds and thus malfunctions.

Normal Pressure Hydrocephalus

Normal pressure hydrocephalus (NPH), also termed symptomatic hydrocephalus, is a type of brain malfunction caused by excessive production of cerebrospinal fluid (CSF). Its typical symptoms are gait disturbance, urinary incontinence, and dementia or mental decline. It is difficult to diagnose because the symptoms are common to several other diseases. The usual treatment is installation of a shunt to drain excess CSF into another part of the body. This treatment can reverse the symptoms and restore normal functioning, or it may do so partially, or it may not succeed.

Symptoms:

Symptoms include difficulty walking, memory loss and inability to control urination.

Brain changes:

Caused by the buildup of fluid in the brain. Can sometimes be corrected with surgical installation of a shunt in the brain to drain excess fluid.

Huntington's Disease

Huntington's disease (HD) is a neurodegenerative genetic disorder that affects muscle coordination and leads to cognitive decline and psychiatric problems. It typically becomes noticeable in mid-adult life. HD is the most common genetic cause of abnormal involuntary writhing movements called chorea, which is why the disease used to be called Huntington's chorea.

Symptoms:

Include abnormal involuntary movements, a severe decline in thinking and reasoning skills, and irritability, depression and other mood changes.

Brain changes:

The gene defect causes abnormalities in a brain protein that, over time, lead to worsening symptoms.

Wernicke-Korsakoff Syndrome

Wernicke-Korsakoff Syndrome (WKS) is a neurological disorder. Wernicke’s Encephalopathy and Korsakoff’s Psychosis are the acute and chronic phases, respectively, of the same disease. Korsakoff syndrome is a chronic memory disorder caused by severe deficiency of thiamine (vitamin B-1). The most common cause is alcohol misuse.

Symptoms:

Memory problems may be strikingly severe while other thinking and social skills seem relatively unaffected.

Brain changes:

Thiamine helps brain cells produce energy from sugar. When thiamine levels fall too low, brain cells cannot generate enough energy to function properly.