Delirium, Dementia, Amnestic Disorder, and Other Cognitive Disorders
Delirium
The "Associated Features" section was modified to emphasize the presence of two varieties of delirium—hyperactive and hypoactive. Text was also added to the "Specific Age Features" section to reflect the finding that advanced age has been found to be a risk factor for delirium in a variety of study populations, even after controlling for other risk factors (like concomitant illness). Prevalence data on delirium in a variety of medically-ill populations are now available (e.g., up to 60% of nursing home residents aged 75 or older may develop delirium). The importance of early recognition and treatment of delirium is highlighted in the substantial additions to the Course section of the text (e.g., individuals with better premorbid cognitive and physical functioning have a better recovery).
Delirium Due to a General Medical Condition
The list of associated general medical conditions was reorganized and updated.
Substance-Induced Delirium
Text was added to clarify that the onset and offset may be affected by various factors such as brain damage, older age, substance half-life, the presence of multiple substances, and poor clearance.
Dementia
Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) includes new diagnostic codes for the dementias (with the exception of Vascular Dementia which remains unchanged). The code for all types of dementia (except Vascular) is 294.10 if the subtype is “Without Behavioral Disturbances,” and 294.11 if the subtype is “With Behavioral Disturbances.” Codable subtypes that previously applied to Dementia of the Alzheimer's Type (e.g., With Depressed Mood) no longer apply. Instead, the corresponding Mental Disorder Due to a General Medical Condition (e.g., 293.83 Mood Disorder Due to Alzheimer's disease) should be coded on Axis I. Because of International Classification of Diseases, Ninth Edition, Clinical Modification (ICD-9-CM) coding conventions, Vascular Dementia codes and subtypes remained unchanged.
The list of causes of dementia was updated to reflect that the most common cause, after Alzheimer's disease, is another neurodegenerative process, such as Lewy body disease or frontotemporal degeneration, two etiologies which are not specifically listed in DSM-IV. Prevalence figures were updated to reflect more recent epidemiological data (i.e., around 1.5% for individuals ages 65-69 years, rising to 16% to 25% for those older than 85 years of age).
Dementia of the Alzheimer's Type
Although an enormous effort has gone toward the development of biological markers for Alzheimer's disease, none of these markers are as yet widely accepted. Text was added to the "Associated Laboratory Features" section (as well as the differential diagnosis section for Dementia) acknowledging that Alzheimer's disease remains a diagnosis of exclusion. The section on Course was updated to highlight the development of personality changes. Prevalence estimates were revised based on the United States General Accounting Office's 1998 report on the prevalence of Alzheimer's. Finally, the "Familial Pattern" section was updated to reflect current data on chromosomal linkage and the role of the genetic marker APO-E4 as a risk factor for the development of late-onset cases.
Dementia Due to Parkinson's Disease/Dementia Due to Pick's Disease
Two of the most common forms of dementia are Lewy body dementia (an example of which is Dementia Due to Parkinson's disease) and frontotemporal dementia (of which Dementia Due to Pick's Disease is an example). Although there was insufficient evidence to justify a radical reorganization of this section, text was added to the sections on Dementia Due to the Other General Medical Conditions, Dementia Due to Parkinson's Disease, and Dementia Due to Pick's Disease to clarify how such cases should be classified.
Dementia Due to Creutzfeldt-Jakob Disease
Text was added regarding the cross-species transmission of prion infections, reflecting the outbreak of a human variant of bovine spongiform encephalopathy in the United Kingdom in the mid-1990s.