[DEMENTIA IN THE MENTAL DISORDERS CHAPTER OF THE WORLD HEALTH ORGANIZATION INTERNATIONAL CLASSIFICATION OF DISEASES:...

During the three decades since the publication of ICD-10 in 1992 and the initial implementation of ICD-11 in 2022, much clinical and research data have been accumulated concerning the various types of dementia. From a classificatory hierarchical standpoint ICD-10 dementia was classed under a simple definition of "mental disorder" that did not cover mild dementia, and also under a wide definition of "organic mental disorders" with reservations concerning the term "organic". The definition of the syndrome of dementia in ICD-10 was etiological, and described a syndrome stemming from brain disease usually chronic or progressive, leading to impaired multiple higher cortical functions. ICD-10 diagnostic guidelines emphasized decline in both memory and thinking, impaired processing of incoming information, and duration of at least 6 months. Dementia in Alzheimer`s disease was its prototype. Dementia in ICD-11 differs from its precedent with changes in classification, content and terminology. In ICD-11 dementia appears under a more specific definition for "mental disorder" and under the restricted diagnostic grouping "neurocognitive disorders". Dementia is currently a polythetic-operational diagnostic system, its definition is symptomatology-based, and essential (required) features include, among others, marked impairment in at least two out of seven cognitive functions, and also neuro-cognitive changes. Without reference to age of onset, duration and course, dementia due to Alzheimer`s disease is one of many types. In both classifications, dementia is not coded. Adding a specific etiology from the chapter itself, or from a different chapter in the classification, changes its nosology status to a disorder which allows coding.