CT Scanning and the Investigation of Dementia: A Review

Structural brain CT changes and cognitive deficits in elderly depressives with and without reversible dementia ('pseudodementia')

Twenty-six elderly (greater than 60 yrs) patients with DSM-III major depression were compared to 13 patients with NINCDS/ADRDA probable Alzheimer's disease (AD), and to 31 screened normal controls. Subjects were matched on age and sex. Fifteen of the 26 depressed patients were cognitively impaired on the Mini-Mental State Examination (MMSE) upon admission, but after treatment returned to the normal range. These 15 patients were defined as having the dementia syndrome of depression (DOD). The remaining 11 depressed patients were termed depressed, cognitively normal (DCN). All subjects received standardized cranial CT scans for assessment of ventricular brain ratio (VBR) and CT attenuation numbers. Subjects also received neuropsychological evaluation. CT values for the 26 depressed patients lay between those of AD patients and normal controls. CT values for the DOD subgroup clustered near those of AD patients. Patterns of cognitive deficits and correlations of CT attenuation values with cognitive measures were also similar in AD and DOD. Most patients were reassessed at a mean of two years after initial testing; of the 11 of the 15 DOD re-examined, only one had undergone cognitive decline. By contrast, all AD patients retested had declined significantly. Episodes of DOD and DCN tended to 'breed true'. This study suggests that while patients with DOD may have underlying structural brain abnormalities, obvious short-term progression to AD does not commonly occur.

Assessing dementia. Part I: Difficulties, definitions and differential diagnosis

Despite the pressures of an increasingly ageing population and an ever increasing scientific knowledge, the clinical characteristics of dementia remain poorly defined. This relative lack of clarity in clinical understanding has led to diverse diagnostic problems, including those of mistaken diagnosis as well as over- and under-diagnosis in different settings. This paper focuses on the syndromal and aetiological diagnosis of dementia by outlining current clinical definitions, considering differential diagnosis in detail and reviewing characteristics of common dementing disorders. The past emphasis on a search for treatable causes, the reliance on laboratory investigations and the concept of subcortical dementia are all questioned. Aspects of evaluation that are stressed include the value of brief objective cognitive testing, a knowledge of normal age-related cognitive changes, flexible criteria for Alzheimer's disease and a comprehensive individualised evaluation of the person. Broader assessment issues will be dealt with in a second paper.

Computed tomography and psychometric test performances in patients with solvent induced chronic toxic encephalopathy and healthy controls

Patients with chronic toxic encephalopathy caused by occupational exposure to organic solvents and diagnosed between 1976 and 1981 have been re-examined during a follow up period of 21-88 months (median 48). Thirty two patients underwent computed brain tomography (CT), were retested psychometrically, and the results were compared with a group of age matched control subjects from the same socioeconomic level. The age of the patients was 33-69 (median 55) and they had been exposed to organic solvents for 7-50 years (median 26). The CT examinations were quantified by linear measurements on the films of the four largest sulci, the minimum width of the cella media and the third ventricle. Bifrontal horn, bicaudate, and third ventricle--Sylvian fissure distances were also measured; and measurements were adjusted for variation in skull diameter. No differences were found between the patients and controls. Most of the measures were correlated with age, to a somewhat higher degree in the patients. The patient-control differences did not increase with increasing age of the subjects. Psychometrically the patients performed worse than the controls despite adjustments for possible differences of intellectual level in the two groups. In the patients correlations were found between some of the CT measures and psychometric test performances suggesting slower psychomotor speed and attention difficulties among subjects with central and cortical brain substance reduction. No such correlation was found in the control group. It is concluded that patients with solvent induced chronic toxic encephalopathy have no severe loss of brain substance.

A variant of normal-pressure hydrocephalus simulating Pick's disease on computerized tomography. Report of two cases

The authors present two cases of normal-pressure hydrocephalus that simulated Pick's disease radiographically and that were initially diagnosed as cortical atrophy. In both cases, Sylvian cisternoperitoneal shunts improved the clinical picture only temporarily, but ventriculoperitoneal shunting produced dramatic relief of all symptoms.