The various types of dementia

Dementia is defined as acquired global impairment of intelligence, memory and personality without impairment of consciousness (Lishman, 1998). It is usually progressive disease. Dementia is caused by various types of diseases.

In dementia cognitive functions such as memory, language, abstract thinking and judgment, movements, visuospatial skills and personality are deteriorated. In dementia consciousness is normal except in lewy body dementia.

Alzheimer’s disease

This disease accounts for 50 -60% of all dementias. Prominent features are memory loss, especially short term memory, difficulty in speaking, difficulty in walking, and behavioral disturbances such as wandering.

In addition, patients with Alzheimer’s disease show impaired sense of smell in the early course of the disease. It is a progressive disease and usual life expectancy is 5 – 8 years.

This is the second commonest cause of dementia. Around 20 -25 percent of the demented patients have vascular dementia. It is disease characterized by small brain infarctions caused by atherosclerosis. In these patients there are other co-existing vascular diseases such as heart attacks and peripheral vascular disease in the limbs.

Sudden personality change is the usual early presentation. For an example person with previous good social character may speak filth words in public. In addition, these patients show labile mood. However, there insight seems to be preserved. Memory loss usually occurs late. Disease is progressed in stepwise manner. It is more common in men with history of heavy smoking.

Around 15 -20% of patients with dementia are in this category. This disease is characterized by fluctuating alertness, symptoms of Parkinson’s disease (rigidity, slow movements, resting tremors), visual hallucinations and frequent falls.

This disease is characterized by the presence of lewy bodies inside the affected neurons. These lewy bodies are also seen in the neurons affected by Parkinson’s disease. Patients get this illness usually before 70 years.

Other types of dementias are Fronto temporal dementia characterized by change of behavior, speech problems (Expressive dysphasia), and early loss of insight and early manifestation of primitive reflexes such as sucking reflex seen in infants.

In addition, Hungtington’s disease, Prion diseases and normal pressure hydrocephalus can cause dementia. Prion diseases are transmissible and common disease is Creutzfeldt–Jakob’s disease. Normal pressure hydrocephalus is the only treatable type of dementia.