HIV/AIDS is a disorder of the immune system (the part of the body that fights off disease and infection) caused by a virus that can also destroy brain tissue. Dementia due to HIV/AIDS is characterized by forgetfulness, slowness, and difficulties with concentration and problem solving. It can also include apathy (a lack of energy, interest, and/or emotion) and psychotic symptoms, such as delusions (fixed, false beliefs) and hallucinations (hearing, seeing, touching, tasting, or smelling things that are not truly present). Because HIV/AIDS affects people of all ages, dementia due to HIV/AIDS can occur in children as well as adults.
Dementia due to head trauma can result from a single major head injury (such as a blow to the head during a car accident) or from a repeated series of head injuries, such those sustained by football players or boxers (sometimes called dementia pugilistica). The degree and nature of cognitive impairment due to head trauma depends on the location and severity of the brain injury. People with this type of dementia often experience amnesia (an inability to learn and recall new information and/or remember previously learned information or past events), persistent memory loss, irritability, problems sustaining attention, depression, apathy, and other personality changes. This kind of dementia is most common among young men who engage in highly risky behaviors such as riding a motorcycle without a helmet and driving while intoxicated. For more information about closed head injuries, please read our Traumatic Brain Injury article.
Parkinson's Disease is caused by a lack of cells that produce dopamine (a neurotransmitter, or chemical that transmits messages in the brain and nervous system). This disorder affects movement by creating tremors (shaking or trembling, sometimes limited to a certain part of the body such as arms or legs), rigidity, and other problems with balance and motor skills. About 20-60% of people with Parkinson's Disease also develop dementia. Dementia due to Parkinson's Disease causes difficulty retrieving memories, depression, and problems making decisions and carrying out daily tasks. Interestingly, the brains of people with dementia due to Parkinson's Disease often appear to have damage that is similar to the brains of people with Alzheimer's Disease or Lewy Body Disease when they are examined during an autopsy.
Huntington's Disease is a genetic (inherited) condition that affects cognition, emotion, and movement. It can start as early as 4 years of age or as late as 85 years of age, but most commonly affects people in their late 30s or early 40s. When Huntington's causes dementia, a primary symptom is difficulty retrieving memories. For instance, people with dementia due to Huntington's might have trouble remembering where they went to college or what they did on their last birthday. Other symptoms include problems with executive functioning (the ability to plan and carry out daily tasks), and impaired judgment. Memory deficits become more severe as the disease progresses, and some people experience delusions (fixed, false beliefs) and hallucinations (sensing things that are not truly present). Children of parents with Huntington's Disease have a 50% chance of developing the disease themselves.
Pick's Disease is the most common of the frontotemporal dementias, a long word which simply means that the frontal (near the forehead) and temporal (side) portions of the brain are affected. Most commonly occurring in people who are between 50 and 60 years old, Pick's Disease is characterized by drastic personality changes, a deterioration of social skills, and emotional blunting (a lack of empathy and emotion). These signs usually occur before problems with memory and other symptoms emerge. In the advanced stages of the disease, people with Pick's Disease may become extremely apathetic or highly agitated, to the point that conducting a psychological assessment (for diagnostic purposes) is impossible because they cannot participate or focus on answering questions.
Creutzfeldt-Jakob Disease (CJD)
Sometimes referred to as "mad cow disease," CJD is caused by "slow viruses" called prions, which are folded proteins that interfere with the brain's ability to function. The disorder usually affects adults between 40 and 60 years of age, but can occur at any age. Anywhere from 5-15% of CJD cases have a genetic component; however, many people have no family history of the disorder. In individuals with no family history of CJD, the disease is often transmitted through infected medical equipment in procedures such as transplantation of the cornea of the eye. Dementia caused by CJD often progresses rapidly over several months and is characterized by problems with attention, concentration, appetite, vision, and coordination.
Normal Pressure Hydrocephalus
Normal Pressure Hydrocephalus occurs when there is an abnormal increase in the level of cerebrospinal fluid (the fluid in and around the brain and spinal cord which serves a protective, nourishing function) in the brain's hollow spaces (called ventricles). This increased fluid level squeezes the brain, which can cause subsequent damage. In addition to dementia, people with this disorder often experience problems walking and controlling their bladder.
Wernicke-Korsakoff Syndrome results from a deficiency in thiamine (Vitamin B1) and is often the result of chronic, severe alcoholism. This syndrome can also result from general malnutrition, severe eating disorders, or the effects of chemotherapy (often used in cancer treatment). Dementia due to Wernicke-Korsakoff Syndrome is characterized by confusion, apathy (a lack of energy, interest, and/or emotion), an inability to engage in meaningful conversation (i.e., impaired ability to discuss current events or one's outlook on life), hallucinations (sensing things that are not truly present), and severe memory impairment.
Dementia caused by multiple medical conditions is called Mixed Dementia or - in the DSM-IV - dementia due to "multiple etiologies." The most common form of Mixed Dementia is dementia due to both Alzheimer's and Vascular Disease, both of which we describe below.
Dementia can also be caused by the persisting effects of a substance (e.g., an illegal drug; over-the-counter or prescription medication; or a toxin such as mercury, lead, or carbon monoxide).
In cases where a clear reason for the dementia cannot be determined, the dementia is referred to as Dementia NOS (not otherwise specified). There are a couple of reasons a diagnosis of Dementia NOS might be given. For example, a person may clearly show signs of dementia, but the clinician does not have enough information to make an accurate diagnosis. In this case, the NOS is a temporary diagnosis that will be changed once the clinician has gathered more information. In rare cases, every known cause of dementia is ruled out (e.g., found not to be a cause), so a diagnosis of Dementia NOS is given because the reason for the person's symptoms is truly unknown.