What Are the Different Types of Dementia?

While Schizophrenia is considered a young person's disease, Dementia is considered a disease of the elderly. According to the DSM-IV-TR (The Diagnostic and Statistical Manual IV-TR) the prevalence of occurrence is 1.4% to 1.6% in individuals 65-69 and rises to 16% to 25% in those over 85. While both illnesses include changes in thinking, Dementia requires cognitive impairment (including memory impairment). No matter what kind of Dementia is diagnosed, all will include memory impairment. Aside from memory impairment one of the following deficits must also be present - aphasia, apraxia, agnosia or a disturbance in executive functioning.

What are the various types of etiology of Dementia?

1. Dementia of the Alzheimer's Type - Aside from the above criteria this type of Dementia requires a gradual but continual decline in cognitive functioning. This diagnosis can only be made after all other etiologies have been ruled out because of the clinical difficulty in accurately diagnosing Alzheimer's disease. If the diagnosis comes before age 65 it is considered early onset. Late onset would occur after age 65. People with this type of Dementia may or may not have behavioral issues like wandering and agitation.

2. Vascular Dementia - Along with the basic deficits individuals with this diagnosis have neurological signs which are observable and can be seen in CT tests and MRI imaging showing vascular legions in the brain. They may have weakness in their extremities, walk with a strange gait, and other neurological signs. Because this diagnosis involves changes occurring in the brain they may also experience delirium (difficulty remaining conscious) and delusions (bizarre think and a disconnect from reality). While a single stroke does not usually cause Vascular Dementia, multiple strokes can. Onset is usually abrupt and only certain brain functions may be affected depending on the location of the strokes.

3. Dementia Due to Other General Medical Conditions - Along with the required symptoms the doctor must establish the presence of a medical condition affecting temporal association and be able to correlate the beginning of symptoms to the beginning of the other medical conditions. He also has to rule out any of the other types of etiology before he can make this diagnosis.

4. Dementia Due To HIV Disease - A diagnosis of HIV must precede the diagnosis of Dementia. Doctors can tell by spinal tap if the HIV infection involves the nervous system. People with this type of Dementia are usually forgetful, have poor concentration, move slowly, and have difficulty problem solving. Occasionally they may also have delirium, delusions and hallucinations. They may have tremors, rapid eye movements, imbalance and other neurological complications.

5. Dementia Due to Head Trauma - This diagnosis is made when the dementia is a result of a blow to the head. Posttraumatic amnesia is often present along with persistent memory impairment. Head injuries of this magnitude are often found in young males with high risk behaviors or sports related injuries. It is usually non-progressive unless the head injuries continue (as in boxing).

6. Dementia due to Parkinson's Disease - A person must be diagnosed with Parkinson's Disease which is a slowly progressive neurological condition characterized by tremor, rigidity, and postural instability. Between 20%-60% of individuals with Parkinson's will present with symptoms of Dementia and they are usually advanced in age. Dementia associated with Parkinson's is characterized by a slowing of thinking and moving, the loss of the ability to care for one's daily functions and poor memory retrieval.

7. Dementia Due to Huntington's Disease - A person must be diagnosed with Huntington's disease which is an inherited progressive degenerative disease of cognition, emotion, and movement. Though diagnosis has been made as early as 4 years of age, it is usually diagnosed in the late 30's and early 40's. Late onset may come as late as 85. Those with Huntington's will experience changes in personality and behavior and they may become depressed, irritable and anxious. The symptoms of Dementia usually are difficulties with memory retrieval, very poor judgment, and an inability to take care of daily functions. This disease is progressive. Offspring of individuals with Huntington's Disease have a 50% chance of developing the disease.

8. Dementia Due to Pick's Disease - Pick's disease is a degenerative disease of the brain which brings about personality changes, deterioration in social skills, emotional blunting, disinhibition and language abnormalities. Brain imaging reveals atrophy in the frontal and/or temporal lobe. This disorder manifests itself in people ages 50 to 60 although it may occur older. It is often difficult to diagnose Pick's Disease as it resembles Alzheimer's so closely.

9. Dementia Due to Creutzfeldt-Jakob Disease - This disease usually is diagnosed in people 40-60 years of age and may have a genetic component. It is a disease of the central nervous system caused by "slow viruses". This is a rapidly progressing disease with rapidly progressing dementia.

10. Substance Induced Persisting Dementia - While this diagnosis may come about as a result of continued voluntary substance abuse, it also may be a result of exposure to a toxin or an allergic reaction to a medication. However, to be diagnosed with Dementia the symptoms must remain after to toxin or substance is out of the system and what remains are the persisting effects of the exposure. The deficits are usually permanent and may worsen even if the substance is no longer present though it is possible to show some improvement over time. Onset is rarely before age 20 and is insidious and slow in progression. Most people with this diagnosis will also qualify for a diagnosis of substance Dependence.

11. Dementia due to Other General Medical Conditions - Dementia may be caused by numerous other assaults on the brain including tumors, concussion, endocrine conditions, nutritional conditions, immune diseases, infections, and other neurological conditions.

Sources

American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision. Washington DC, American Psychiatric Association 2000