Mohammed T. Abou-Saleh

Principles and Practice of Geriatric Psychiatry.Editors: Professor John R. M. Copeland, Dr Mohammed T. Abou-Saleh and Professor Dan G. BlazerCopyright & 2002 John Wiley & Sons LtdPrint ISBN 0-471-98197-4 Online ISBN 0-470-84641-036Nosology of DementiaIngmar Skoog 1 and John R. M. Copeland 21 Institute of Clinical Neuroscience, University of Go¨teborg, Sweden, and2Royal Liverpool University Hospital, Liverpool, UKIn the early 1950s, Sir Martin Roth defined dementia as ‘‘severedecline in memory accompanied by disorientation for time andplace’’. The modern criteria emphasize that dementia is a globaldecline of intellectual functions that affects more areas than justmemory. However, memory impairment is mandatory for thediagnosis in the Diagnostic and Statistical Manual of MentalDisorders, Version III—Revised (DSM-III-R) and IV (DSM-IV)(see Tables 36.1 and 36.2), issued by the American PsychiatricAssociation 1,2 and in the International Classification of Disease—Edition 10 criteria for research (ICD-10), issued by the WorldHealth Organization 3 (see Table 36.3). In these criteria, dementiais a syndrome characterized by a decline in memory and otherintellectual functions (e.g. orientation, visuospatial abilities,language, thinking, executive function, problem solving, apraxia,agnosia). It is often accompanied by changes in behaviour orpersonality (e.g. loss of initiative, emotional lability, irritability,apathy, coarsening of social behaviour, change in mood). Theselatter symptoms are mandatory for a diagnosis in ICD-10,diagnostic in the presence of memory dysfunction in DSM-III-Rand not included in DSM-IV.An interesting difference between DSM-III-R and DSM-IV isthat DSM-III-R requires impairment in short and long-termmemory, while DSM-IV states that the impairment should includeimpairment in either short or long-term memory. In DSM-IV, incontrast to DSM-III-R and ICD-10, the criteria for dementia areintegrated with the criteria for different types of dementia (such asAlzheimer’s disease and vascular dementia). It is thus notpermitted to diagnose the dementia syndrome per se, but thesubcriteria for dementia are identical for all types.The symptoms of dementia are on a continuum with normalbehaviour, which often makes it difficult to know where the lineshould be drawn between normal function and mild dementia. Thisdimensional rather than categorical character makes mild dementiadifficult to separate from normal ageing 4 . Fairly smalldifferences in criteria may have large effects on the prevalencerates. Mowry and Burvill 5 found a variation in the prevalence ofmild dementia ranging from 3% to 64% when different criteriawere used on the same population. Different criteria also diagnoseddifferent individuals. If a decline from a previously higher level canbe shown (by obtaining information from key informants or byfollowing the patients over time), the validity may be higher 6 . TheDSM-III-R, DSM-IV and ICD-10 use the degree of socialconsequences of the disorder [‘‘sufficient to interfere with everydayactivities’’ (ICD-10) and ‘‘significant impairment in social oroccupational functioning representing a significant decline from aprevious level of functioning’’ (DSM-IV)] as the criterion fordemarcating normal from abnormal behaviour.The modern concept of dementia does not imply anythingabout prognosis, i.e. the course may be progressive, static,fluctuating or even reversible.DIFFERENT TYPES OF DEMENTIAA dementia syndrome may be caused by more than 70 diseases,the most common being Alzheimer’s disease and vasculardementias.Alzheimer’s DiseaseThe neuropathology of Alzheimer’s disease (AD) is characterizedby a marked degeneration of the neurons and their synapses andthe presence of extensive amounts of extracellular senile plaquesand intracellular neurofibrillary tangles in certain areas of thebrain. The typical insidious onset and gradually progressivecourse is emphasized in the National Institute of Neurologicaland Communicative Disorders and Stroke and the Alzheimer’sDisease and Related Disorders Association (NINCDS–ADRDA)criteria (Table 36.4), in DSM-III-R and in DSM-IV but not inICD-10. Memory disturbance is the most prominent earlysymptom, but slight impairment of visuospatial functioning,language and concentration may occur. In the later stages, thesymptomatology is more widespread. The NINCDS–ADRDAcriteria, DSM-III-R, DSM-IV and ICD-10 require that thediagnosis of AD should be made in the absence of diseasesthat, in and of themselves, could account for the progressivedeficits in memory and cognition. Possible AD, according to theNINCDS–ADRDA criteria, may be diagnosed in the presence ofother diseases if they are not judged to have caused thedementia.Alzheimer’s disease is categorized into an early- and a late-onsetform in DSM-IV and ICD-10, based on whether onset occurredbefore or after age 65 years. ICD-10 also specifies that the earlyonsettype should have a relatively rapid onset and progression oraphasia, agraphia, alexia, acalculia or apraxia, while the late-onsettype should have a very slow, gradual onset and progression orpredominance of memory impairment. Another subdivision isbetween familial AD (FAD) and sporadic AD. FAD has anautosomal dominant inheritance. Almost all cases with FAD havean early onset, while most cases of sporadic AD occur late in life.Familial clustering may occur also in sporadic AD 8 .Principles and Practice of Geriatric Psychiatry, 2nd edn. Edited by J. R. M. Copeland, M. T. Abou-Saleh and D. G. Blazer&2002 John Wiley & Sons, Ltd