|The ICD-10 Classification of Mental and Behavioural
World Health Organization, Geneva, 1992
Dementia in Alzheimer's Disease
Alzheimer's disease is a primary degenerative cerebral disease
of unknown etiology, with characteristic neuropathological and
neurochemical features. It is usually insidious in onset and
develops slowly but steadily over a period of years. This period
can be as short as 2 or 3 years, but can occasionally be
considerably longer. The onset can be in middle adult life or even
earlier (Alzheimer's disease of presenile onset), but the
incidence is higher in later life (Alzheimer's disease of senile
onset). In cases with onset before the age of 65-70, there is the
likelihood of a family history of a similar dementia, a more rapid
course, and prominence of features of temporal and parietal lobe
damage, including dysphasia or dyspraxia. In cases with a later
onset, the course tends to be slower and to be characterized by
more general impairment of higher cortical functions. Patients
with Down's syndrome are at high risk of developing Alzheimer's
There are characteristic changes in the brain: a marked
reduction in the population of neurons, particularly in the
hippocampus, substantia innominata, locus ceruleus, and
temporoparietal and frontal cortex; appearance of neurofibrillary
tangles made of paired helical filaments; neuritic (argentophil)
plaques, which consist largely of amyloid and show a definite
progression in their development (although plaques without amyloid
are also known to exist); and granulovacuolar bodies.
Neurochemical changes have also been found, including a marked
reduction in the enzyme choline acetyltransferase, in
acetylcholine itself, and in other neurotransmitters and
As originally described, the clinical features are accompanied
by the above brain changes. However, it now appears that the two
do not always progress in parallel: one may be indisputably
present with only minimal evidence of the other. Nevertheless, the
clinical features of Alzheimer's disease are such that it is often
possible to make a presumptive diagnosis on clinical grounds
Dementia in Alzheimer's disease is at present irreversible.
The following features are essential for a definite diagnosis:
(a) Presence of a dementia as described above.
(b) Insidious onset with slow deterioration. While the onset
usually seems difficult to pinpoint in time, realization by others
that the defects exist may come suddenly. An apparent plateau may
occur in the progression.
(c) Absence of clinical evidence, or findings from special
investigations, to suggest that the mental state may be due to
other systemic or brain disease which can induce a dementia (e.g.
hypothyroidism, hypercalcaemia, vitamin B12 deficiency, niacin
deficiency, neurosyphilis, normal pressure hydrocephalus, or
(d) Absence of a sudden, apoplectic onset, or of neurological
signs of focal damage such as hemiparesis, sensory loss, visual
field defects, and incoordination occurring early in the illness
(although these phenomena may be superimposed later).
In a certain proportion of cases, the features of Alzheimer's
disease and vascular dementia may both be present. In such cases,
double diagnosis (and coding) should be made. When the vascular
dementia precedes the Alzheimer's disease, it may be impossible to
diagnose the latter on clinical grounds.
* primary degenerative dementia of the Alzheimer's type
Consider: a depressive disorder (F30-F39); delirium (F05); organic
amnesic syndrome (F04); other primary dementias, such as in
Pick's, Creuzfeldt-Jakob or Huntington's disease (F02.-);
secondary dementias associated with a variety of physical
diseases, toxic states, etc. (F02.8); mild, moderate or severe
mental retardation (F70-F72).
Dementia in Alzheimer's disease may coexist with vascular
dementia (to be coded F00.2), as when cerebrovascular episodes
(multi-infarct phenomena) are superimposed on a clinical picture
and history suggesting Alzheimer's disease. Such episodes may
result in sudden exacerbations of the manifestations of dementia.
According to postmortem findings, both types may coexist in as
many as 10-15% of all dementia cases.
Dementia in Alzheimer's disease beginning before the age of 65.
There is relatively rapid deterioration, with marked multiple
disorders of the higher cortical functions. Aphasia, agraphia,
alexia, and apraxia occur relatively early in the course of the
dementia in most cases.
As for dementia, described above, with onset before the age of
65 years, and usually with rapid progression of symptoms. Family
history of Alzheimer's disease is a contributory but not necessary
factor for the diagnosis, as is a family history of Down's
syndrome or of Iymphoma.
* Alzheimer's disease, type 2
* presenile dementia, Alzheimer's type
Dementia in Alzheimer's disease where the clinically observable
onset is after the age of 65 years and usually in the late 70s or
thereafter, with a slow progression, and usually with memory
impairment as the principal feature.
As for dementia, described above, with attention to the
presence or absence of features differentiating the disorder from
the early-onset subtype (F00.0).
* Alzheimer's disease, type 1
* senile dementia, Alzheimer's type
Dementias that do not fit the descriptions and guidelines for
either F00.0 or F00.1 should be classified here; mixed Alzheimer's
and vascular dementias are also included here.
ICD-10 copyright © 1992 by World
AZ Psychiatry copyright
by Dr. Manaan Kar Ray