The connection between stroke and dementia is slowly becoming more and more apparent. But what does the word "dementia" really mean? Depending on the context in which it is used, the word dementia evokes different mental pictures in different people. For some people, the word might evoke the image of a middle aged person with a severe psychiatric disturbance. For others it might bring up the image of a quiet and disheveled elderly man. So which is it? Before proceeding with the subject of stroke-induced dementia, let’s first clarify a few things about this condition.
What is Dementia?In general terms, dementia is a global brain disorder in which multiple aspects of brain function are persistently compromised in a way that interferes with a person's normal everyday functioning. However, dementia is not a single disorder. There are a myriad of disease processes which can lead to dementia, each one of which induces a different pattern of behavioral changes.
For instance, Alzheimer disease, perhaps the most well known dementia of all, starts off late in the life (commonly between the ages of 65-85) and progresses slowly. Its most prominent symptoms include memory loss, delusions, hallucinations, anxiety, sleep disturbances, and depression. By contrast, fronto-temporal dementias start off earlier in life (between the ages of 50-60) and although they still progress slowly, they do so a little more rapidly than Alzheimer disease. Their most prominent features include personality changes such as loss of insight, loss of empathy for others, poor self-care, emotional explosiveness, and impulsiveness.
Here is a list of the most common types of dementia:
- Alzheimer Disease (AD): A disease originally described in 1907 by the German psychiatrist Alois Alzheimer, AD leaves the brains of those affected by it with a characteristic appearance under the microscope, which is mainly due to widespread presence of the so called "neuritic plaques" and neurofibrillary tangles.
- Frontotemporal Dementia: This is a group of disorders in which the frontal and temporal lobes of the brain are selectively affected. They typically include the following subtypes of dementia:
- Dementia with Lewy Bodies: A type of dementia characterized by at least two of the following three symptoms. 1) A waxing and waning level of consciousness; 2) visual hallucinations and 3) spontaneous movements suggestive of Parkinson's disease.
- Parkinsonian Dementias: This is a group of dementias which always occur in the context of the progressive movement abnormalities typical of Parkinson's disease. These include tremors, gait disturbances, and spasticity. The common Parkinsonian dementias are:
- Degenerative (sporadic) dementias
- Degenerative familial dementias
- Secondary Parkinsonian dementia syndromes
- Dementia pugilistica
- Dementia due to inherited metabolic disorders
Vascular DementiaThis is the type of dementia caused by strokes, ministrokes, silent strokes, and other forms of vascular disease.
The history of this subject begins in the 1800s and early 1900s when the term apoplectic dementia gained popularity as a medical term which described the abrupt decline in mental function experienced by some stroke survivors. It later became accepted that “hardening of the brain arteries” could cause dementia due to a poorly understood damage to the brain. It took several decades until the 1970s when investigators found that the stroke-induced damage to the brain their predecessors had proposed consisted of a loss of brain volume from multiple strokes. In other words, it suddenly became clear that the cumulative effects of multiple strokes on the brain could lead to dementia.
This gave birth to the term “vascular dementia” or “multi-infarct dementia”, which became the preferred term to define the specific pattern of cognitive decline associated with having multiple strokes. In recent years, however, this term has fallen out of favor as new imaging techniques have shown that even single strokes, referred by some as “strategic strokes,” can also cause someone to become demented. What’s more, in some cases, no clear strokes at all, but a condition closely associated with strokes which is known as “white matter disease” (also known as microvascular disease or chronic ischemic brain changes) has also been associated with the onset of dementia.
Vascular Cognitive ImpairmentThe term "vascular cognitive impairment," or VCI for short, has more recently been proposed as a term that encompasses the different degrees of cognitive impairment commonly seen in people who have suffered strokes, or who are known to be affected with white matter disease. Thus, the whole spectrum of cognitive changes caused by vascular disease and stroke, which are thought to range from very mild, but detectable forms of cognitive impairment, to severe forms of dementia, can now be grouped under this new term.
One of the most important advances in this field in recent years is the realization that the very risk factors that make people susceptible to stroke can also increase their risk of acquiring vascular dementia.
Suggested reading: Six ways to stay stroke-free
Bradley G Walter, Daroff B Robert, Fenichel M Gerald, Jancovic, Joseph Neurology in clinical practice, principles of diagnosis and management. Fourth Edition, Philadelphia Elsevier, 2004.
Paige Moorhouse and Kenneth Rockwood; Vascular cognitive impairment: current concepts and clinical developments; Lancet Neurology; 2008; 7:246-55