Dementia due to Other Causes

Key points

Dementia may develop as a result of many other conditions, such as:

1. Progressive medical conditions of the brain. For example:

   • Dementia with Lewy bodies (Lewy body dementia)

     This is a type of progressive dementia that occurs sporadically. It is caused by the death of cells in the basal ganglia and a part of the brain called the substantia nigra. The remaining living nerve cells in the substantia nigra are then unable to produce enough dopamine, a neurotransmitter essential for the brain to control body movement, and they contain abnormal microscopic protein deposits called Lewy bodies that cause the brain to deteriorate. Patients will show a progressive decrease in cognitive functioning similar to that found with Alzheimer's disease, and impaired motor control similar to that of Parkinson's disease, along with a variety of possible symptoms including visual hallucinations, confusion, daily changes in attention and alertness, sleep disorders and frequent falls. There is no cure for dementia with Lewy bodies at the moment.

   • Frontotemporal dementia (frontal lobe dementia, including Pick's disease)

     This is an inherited disease estimated to account for as much as 10% of dementia cases. It is caused by the degeneration of nerve cells mainly in the frontal and temporal lobes of the brain due to abnormal tau that aggregates into neurofibrillary tangles, causing cells to die. Most patients start to have symptoms between the ages of 40 and 65. They usually have problems in judgment such as inability to recognize taunts, humour, and emotions of other people, resulting in them being easily cheated. They may also display inappropriate social behavior, such as being easily irritated, showing compulsive behavior, being impolite and having unusual stubbornness. However, their memory is often normal in the early stage of the disease.

   • Parkinson's disease dementia

     This develops in about 20% of people with Parkinson's disease. Parkinson's disease is a progressive brain disease caused by the deterioration of nerve cells in the substantia nigra. Only nerve cells in the substantia nigra can produce dopamine, an important chemical that allows the brain to control body movement. Most of the patients are over the age of 60 and develop Parkinson's disease dementia 10 to 15 years after being diagnosed with Parkinson's disease. Parkinson's disease dementia is especially prevalent among Parkinson's patients who have hallucinations and severe motor control problems.

   • Huntington's disease dementia (an inherited disease)

     This inherited disease is caused by a faulty gene that causes progressive degeneration of brain cells in various areas of the brain, resulting in involuntary movements of the body, lost of cognitive ability and emotional distress. Most patients show symptoms in their 30s or 40s. Patients who show symptoms in their 60s often get diagnosed with other diseases as they may only have depressive symptoms while their cognitive abilities remain intact.

2. Dementia related to malnutrition and dehydration

   • Deficiency of vitamin B12, B9 (also known as folic acid) and B1 (also known as thiamine) can induce symptoms of dementia.
   • Dehydration can induce symptoms of dementia.
   • Symptoms of dementia in people with a deficiency of vitamins may be alleviated by taking supplements. In some cases, symptoms might even be eliminated.

3. Dementia due to trauma

   This includes posttraumatic dementia that happens after open or closed head injuries, as well as dementia pugilistica, also known as chronic traumatic encephalopathy and boxer's syndrome. This is caused by single or repetitive brain injuries. People with posttraumatic dementia may show impairment in long-term memory after a single head injury. People with dementia pugilistica often start to show symptoms of decline in cognitive abilities and symptoms of Parkinson's disease about 16 years after the first incident of repetitive head injuries.

4. Dementia due to toxic substances

   • Excessive consumption of alcohol may cause alcoholic dementia. Reactions to some medications, side effects of specific medications, overdoses of specific medications, and drug abuse may induce symptoms of dementia. Stopping the use of alcohol and cutting the use of medications may reduce or even eliminate symptoms depending on the degree of damage to the brain.
   • Excessive intake of heavy metals such as lead, mercury, arsenic and manganese can induce metallic dementia.
   • Excessive intake of solvents and some insecticides can induce dementia due to organic poisons.

5. Dementia due to infections

   Infections that can affect the brain may cause dementia, including acquired immune deficiency syndrome (AIDS), Creutzfeldt-Jakob disease, opportunistic infections, various encephalitis (such as herpes encephalitis, fungal encephalitis and bacterial encephalitis), various meningitis (such as fungal meningitis and bacterial meningitis) and neurosyphilis (general paresis).

6. Other medical conditions

   Medical conditions such as liver disease, kidney disease, insulin resistance, metabolic disorders, endocrine disorders and brain tumors can also induce dementia. In some cases, the symptoms could be reduced or even eliminated with appropriate medical treatment.

7. Depression-related pseudo-dementia

   As symptoms of depression such as a decline in cognitive functions, a decline in memory and poor concentration are similar to those of dementia, depressive disorders may be confused with dementia. Medical professionals have to identify whether a mood disorder is the cause of the symptoms of dementia, or if dementia is the underlying medical condition causing low mood. Symptoms of dementia may be eliminated with appropriate treatment of the depressive disorder if the person is suffering from depression.