Clinical issues relating to the diagnosis of mild dementia in a British community survey.

Many epidemiologists base their diagnoses of dementia on scores on brief cognitive tests, but the border between normal aging and mild dementia is so poorly understood that simple demarcations cannot adequately encapsulate the wealth of clinical material that needs to be taken into account in assigning diagnostic labels. Data from a British study of the prevalence and natural history of dementia, in which diagnoses of dementia were made by clinicians using a new, standardized interview schedule, are presented to demonstrate the effects of physical disability, psychiatric illness, and other factors on memory impairment and performance in everyday life. Our purpose is not to insist that clinicians are always correct but rather to highlight the complexities involved and the need for investigators to be more open about the way in which they distinguish between physical, psychiatric, and cognitive infirmities.

The progression of mild idiopathic dementia in a community population.

Thirty-one subjects aged 75 years and over who were identified as suffering from mild, idiopathic dementia in a large community survey were reviewed at annual intervals for 2 years. Diagnoses and severity ratings were based on defined criteria following a mental state examination, a medical and psychiatric history, detailed cognitive testing, and an interview with relatives or other key informants. Fourteen subjects became more severely demented within 2 years. The initial cognitive test battery failed to reveal any differences between respondents whose dementia advanced and those whose condition remained unchanged, but, in the former group, subjects' symptoms had been present for longer, and a greater proportion had been recognised as demented, or possibly demented, by their general practitioners. We suggest that subjects whose dementia progressed had actually been more severely disabled at the time of identification.

The reliability and validity of the Mini-Mental State in a British community survey.

The Mini-Mental State (MMSE) was administered to 2302 general practice patients aged 75 yr and over. Those scoring 23 or less and a sample of those scoring 24 or 25 were selected for further investigation using the Cambridge Mental Disorders of the Elderly Examination. Inter-observer reliability was high with a mean kappa value of 0.97. Eighty-six per cent of respondents judged to have organic mental disorders scored 23 or less on the MMSE and 92% of those judged to be cognitively intact scored 24 or more. However, only 55% of respondents who scored 23 or less were demented or delirious while a number of relatively well educated, mildly demented subjects scored 24 and 25. The customary cut-off point of 23/24 may need to be revised in future community studies. MMSE scores cannot be used to make even tentative psychiatric diagnoses; more detailed investigation of low scorers is essential.

Memory and growth in the superior temporal gyri.

The superior temporal gyri were measured in 33 infants and in 33 adults. In the adults, most right superior temporal gyri were larger. This asymmetry was not found in infants, a difference which suggests greater growth of the right superior temporal gyri in the population from which our sample was taken. The asymmetry may be related to the functional asymmetry found by Penfield: some of his patients reported re-experiencing of past sensory experiences with electrical stimulation of the temporal lobe. This response was more frequently evoked from the right hemisphere.

Dementia in general practice: the practical consequences of a more positive approach to diagnosis.

General practitioners are often reluctant to administer brief cognitive tests, and to question the relatives of patients who appear to be demented, for fear of causing distress. Diagnoses of dementia are therefore often based on guesswork, and non-demented patients may be rated as cognitively impaired in error. A randomly selected sample of 174 general practice patients aged 80 years and over were asked to complete a simple test of orientation and information in order to assess the usefulness and acceptability of such a procedure. If patients scored 10 points or less out of 12, a relative or other knowledgeable informant was questioned about their changes in mental state and behaviour. Assessments proved acceptable to patients, relatives and doctors; diagnoses were revised in 29 cases; and practical initiatives were proposed in 15 cases. Open discussions with patients and their families proved innocuous and have much to commend them.

Do general practitioners miss dementia in elderly patients?

General practitioners and community nurses were asked to rate the likelihood of dementia for each of their elderly patients. Cases of dementia were identified by research psychiatrists using the Cambridge mental disorders of the elderly examination (CAMDEX), a new structured diagnostic interview. General practitioners correctly identified dementia as at least a possibility in 121 of the 208 cases found. Nevertheless, they mistakenly rated as demented several patients suffering from functional psychiatric disorders, in particular depression. Community nurses correctly identified dementia as at least a possibility in 64 of the 74 demented patients known to them, but they incorrectly suspected dementia in a greater proportion of instances. Both general practitioners and families appeared to have low expectations of what general practice has to offer demented elderly people. General practitioners should take the initiative in diagnosing dementia in very elderly patients who show signs of the condition. In some cases it may be secondary to treatable disorders, and in others all that may be required are understanding, support, and advice to families.

Smooth muscle in human intracerebral arterioles.

Aterioles from the human cerebral cortex have been examined by electron microscopy in several patients aged 43 to 58 years. The wall of all arterioles (ranging in size from 10-70 microns in diameter) is composed of a single layer of endothelium and from one to 5 layers of smooth muscle cells. A basal lamina supports the endothelium and encloses the smooth muscle cells. Smooth muscle cells were identified by morphological criteria that included the presence of dense bodies, abundant microfilaments and numerous pinocytotic vesicles. Some of the intracerebral arterioles were observed in a constricted state indicating functional smooth muscle cells. The presence of functional smooth muscle cells in human intracerebral arterioles indicates that these arterioles are capable of vasoconstriction which may be a possible factor in some clinical conditions.

A follow-up study of dementia diagnosed in the community using the Cambridge Mental Disorders of the Elderly Examination.

Elderly Cambridge residents diagnosed as demented using the Cambridge Mental Disorders of the Elderly Examination (CAMDEX) were reviewed approximately 12 months later. Diagnoses were confirmed in 133 of 137 surviving cases (97%). Subjects said to have minimal dementia (cognitive impairment insufficient to warrant a diagnosis of dementia proper) had a varied outcome. Only 6 out of 29 survivors showed progressive intellectual deterioration and 13 were reclassified as normal. Subjects passed as normal in the first year of the study were reviewed using the Mini-Mental State Examination. We cannot be certain how many were actually dementing, but our findings suggest that only a small number of false negative diagnoses were made in the first year of the study.

Continued clinical validation of dementia diagnosed in the community using the Cambridge Mental Disorders of the Elderly Examination.

We describe the outcome 2 years later of elderly Cambridge residents who had been diagnosed as demented using the Cambridge Mental Disorders of the Elderly Examination. Mortality rates were high but diagnoses were confirmed for all of the 43 moderate and severe cases who survived for this period, and for 51 of the 56 subjects who had been rated initially as mildly demented; 28 of the 56 mildly demented subjects progressed to more severe levels of impairment. As many as 12 of the 24 original minimally demented cases showed evidence of intellectual deterioration, which lends weight to the validity of this experimental category.

The prevalence of dementia as measured by the Cambridge Mental Disorders of the Elderly Examination.

General practice patients aged 75 years and over were screened for cognitive impairment using the Mini-Mental State Examination. Those scoring 23 or below and a sample of those scoring 24 or 25 were assessed using the Cambridge Mental Disorders of the Elderly Examination (CAMDEX), a structured interview schedule specifically designed to detect mild dementia. The CAMDEX includes a mental state examination, a psychiatric history, detailed cognitive testing and an information interview. The prevalence of dementia in 2311 patients was found to be 10.5%, about half that found in most earlier studies. Possible reasons for this low rate are discussed.