Determination of the etiology of delirium is based on the clinical interpretation of the data that has been obtained. The main categories of disorders that must be excluded include infections, metabolic and endocrine disorders, trauma, nutritional or exogenous influences, neoplasms, the effects of drugs or substance abuse.
The DSM-IV defines delirium as "a disturbance of consciousness and changes in cognitive processes that develop over a short period of time" (American Psychiatric Association, DSM-IV). Delirium is characterized by easy distractibility of patients, impaired concentration, memory impairment, disorientation, and speech impairment.
Dementia with Lewy bodies is one of the most common forms of dementia. The disease is characterized by progressive impairment of memory, speech, praxis, and thinking. Distinctive clinical features of dementia with Lewy bodies are fluctuations in mental status, transient states of confusion, hallucinations (most often visual), and increased sensitivity to neuroleptics.
Risk factors for stroke are also risk factors for vascular dementia. They include hypertension, diabetes, atrial fibrillation, smoking, coronary heart disease, heart failure, carotid murmur, alcohol abuse, advanced age, and male gender.
In the United States, vascular dementia is the second most common disease after Alzheimer's disease. In some other parts of the world where stroke rates are very high, vascular dementia is more common than Alzheimer's disease.
To date, the FDA has approved four acetylcholinesterase inhibitors—tacrine, donepezil, rivastigmine, and galantamine—for mild to moderate Alzheimer's disease, and the NMDA glutamate receptor antagonist memantine for severe dementia.
A clinical diagnosis of possible Alzheimer's disease can be established in the presence of dementia syndrome in the absence of other neurological, psychiatric or systemic diseases capable of causing dementia, but with atypical onset, clinical manifestations or course; the presence of a second systemic or neurological disease that can cause dementia, but cannot be considered as the cause of dementia in this case;
Macroscopic changes in Alzheimer's disease include diffuse brain atrophy with decreased convolutional volume and widened sulci. Histopathological examination of patients with Alzheimer's disease reveals senile plaques, neurofibrillary tangles, and decreased neuronal numbers.
Alzheimer's disease is the most common cause of dementia in the Western Hemisphere, accounting for more than 50% of cases. The prevalence of Alzheimer's disease increases with age. Women are more likely to be affected by the disease than men.
This article presents the diseases that most often cause dementia: Alzheimer's disease, vascular dementia, HIV encephalopathy (AIDS dementia), and Ley body dementia. Together, they account for more than 80% of dementia cases.
