Computerized tomography, atrophy and dementia: a review

Association of brain white matter lesions and atrophy with cognitive function in chronic kidney disease

OBJECTIVES

Cognitive impairment is common in patients with chronic kidney disease (CKD), possibly leading to poor outcomes. However, the correlation between brain structural abnormalities and cognitive impairment remains unclear. The aim of this study was to investigate the impairment of specific cognitive domains and their association with brain structural abnormalities.

METHODS

Patients with CKD of at least stage 3 who were not on hemodialysis were enrolled. All participants underwent comprehensive neuropsychological testing in five cognitive domains. Ventricular atrophy, sulcal atrophy, medial temporal atrophy, and white matter changes were assessed using brain magnetic resonance imaging according to standard protocols.

RESULTS

Eighty-seven patients and 50 controls were enrolled. Patients with CKD exhibited decreased cognitive function relative to controls. Compared with patients with stage 3 CKD, those with advanced stage (stages 4 or 5) had poorer cognitive performance, more pronounced white matter hyperintensity (WMH) and more severe ventricular atrophy. Among CKD patients, executive function (β = -.23, P = .043) and attention (β = -.29, P = .004) were associated with WMH in controlled analyses. However, no cognitive impairment was associated with ventricular atrophy.

CONCLUSION

Patients with CKD exhibited cognitive impairment and brain structural abnormalities including WMH and general brain atrophy. Impairment of attention and executive dysfunction were associated with WMH.

Practical one-dimensional measurements of age-related brain atrophy are validated by 3-dimensional values and clinical outcomes: a retrospective study

Background

Age-related brain atrophy has been represented by simple 1-dimensional (1-D) measurements on computed tomography (CT) for several decades and, more recently, with 3-dimensional (3-D) analysis, using brain volume (BV) and cerebrospinal fluid volume (CSFV). We aimed to show that simple 1-D measurements would be associated with 3-D values of age-related atrophy and that they would be related to post-traumatic intracranial hemorrhage (ICH).

Methods

Patients ≥60 years with head trauma were classified with central atrophy (lateral ventricular body width >30 mm) and/or cortical atrophy (sulcus width ≥2.5 mm). Composite atrophy was the presence of central or cortical atrophy. BV and CSFV were computed using a Siemens Syngo workstation (VE60A).

Results

Of 177 patients, traits were age 78.3 ± 10, ICH 32.2 %, central atrophy 39.5 %, cortical atrophy 31.1 %, composite atrophy 49.2 %, BV 1,156 ± 198 mL, and CSFV 102.5 ± 63 mL. CSFV was greater with central atrophy (134.4 mL), than without (81.7 mL, p < 0.001). BV was lower with cortical atrophy (1,034 mL), than without (1,211 mL; p < 0.001). BV was lower with composite atrophy (1,103 mL), than without (1,208 mL; p < 0.001). CSFV was greater with composite atrophy (129.1 mL), than without (76.8 mL, p < 0.001). CSFV÷BV was greater with composite atrophy (12.3 %), than without (6.7 %, p < 0.001). Age was greater with composite atrophy (80.4 years), than without (76.3, p = 0.006). Age had an inverse correlation with BV (p < 0.001) and a direct correlation with CSFV (p = 0.0002) and CSFV÷BV (p < 0.001). ICH was greater with composite atrophy (49.4 %), than without (15.6 %; p < 0.001; odds ratio = 5.3). BV was lower with ICH (1,089 mL), than without (1,188 mL; p = 0.002). CSFV÷BV was greater with ICH (11.1 %), than without (8.7 %, p = 0.02). ICH was independently associated with central atrophy (p = 0.001) and cortical atrophy (p = 0.003).

Conclusions

Simple 1-D measurements of age-related brain atrophy are associated with 3-D values. Clinical validity of these methods is also supported by their association with post-injury ICH. Intracranial 3-D software is not available on many CT scanners and can be cumbersome, when available. Simple 1-D measurements, using the study methodology, are a practical method to objectify the presence of age-related brain atrophy.

Prefrontal lobotomy and hypofrontality in patients with schizophrenia: an integration of the findings

A case of a schizophrenic patient who suffered a frontal lobotomy is presented as the impetus for a discussion of an alternative neurobiologic model of schizophrenia to integrate the findings of prefrontal lobotomy and "hypofrontality". The proposal that primary temporolimbic pathology may result in secondary hypofunction in the prefrontal lobes is examined in light of current structural neuropathologic evidence. Directions for future research suggested by such a model are explored.

Centrum semiovale white matter CT changes associated with normal ageing, Alzheimer's disease and late life depression with and without reversible dementia

A standardized, reliable means of assessing CT attenuation numbers in the centrum semiovale and surrounding grey matter was developed. This was applied to cranial CT scans of 60 normal controls (36 aged greater than 60 years), 25 elderly patients with major depression (14 of whom had the dementia syndrome of depression), and 10 patients with Alzheimer's disease (AD). Subjects received neuropsychological evaluation. Centrum semiovale (CSO) CT attenuation numbers decreased with increasing age for both white and grey matter. White matter attenuation values best discriminated elderly controls from the three patient groups. Both white and grey matter CSO attenuation values correlated with performance on a number of cognitive tasks.

Brain imaging in dementia of the Alzheimer type

Neuroimaging modalities have increased understanding of brain abnormalities in dementia of the Alzheimer type (DAT), and is important in assessment of dementia syndromes by revealing focal disorders, demonstrating potentially treatable conditions, and by documenting progression of disease severity. Computed tomography (CT) and magnetic resonance imaging (MRI) have delineated structural changes in DAT, including cerebral atrophy associated with cortical sulci widening and ventricular enlargement, and deep white-matter lesions with periventricular distributions. Positron emission tomography (PET) has demonstrated diminished regional glucose metabolism at parietal and temporal lobes in DAT, while frontal hypometabolism tends to occur in more severe cases. Metabolic dysfunction assessed by PET appears to be the first indication of a degenerative cortical process in DAT, while anatomic changes on CT or MRI may become evident later in the disease process. This selective overview provides an analysis of the current status and future prospects of brain imaging in DAT.

Cerebral structure on MRI, Part II: Specific changes in Alzheimer's and Huntington's diseases

Using magnetic resonance (MR) imaging and morphometric techniques, groups of patients with Alzheimer's disease (AD) and Huntington's disease (HD) were compared with a large group of normal control subjects. Measures of volume loss in specific subcortical nuclei and eight cortical regions as well as an index of white matter abnormality were obtained. Results indicated expected widespread cortical volume reductions in AD, which were especially severe in mesial cortices; but comparable reductions were present in subcortical structures, particularly the thalamus. In HD, the greatest reductions were in striatal structures, but significant abnormalities were also detected in the thalamus and inferior cortical areas, especially in mesial temporal lobe structures. Significant degeneration in white matter was present in both groups, but was more dramatic in the HD patients. The significant diencephalic reduction in AD may make an important contribution to early memory deficits in the disorder, which are usually attributed to hippocampal damage. Similarly, damage to both the thalamus and mesial temporal lobe structures may play a role in the memory deficits of HD.

An empirical model for analysing and interpreting ventricular measures

Given the abundant and, at times, contradictory studies of ventricular enlargement in neurological and psychiatric disorders, the current study was carried out to provide an empirical basis for analysing and interpreting these measures. A sample of CT scans on 100 control subject was drawn from the files of the University of British Columbia Department of Radiology and 19 measures of ventricular and head diameter or area were made. The interrelationships of these measures were then examined using factor analytic procedures. Three ventricular dimensions were found. To validate these three dimensions, the relationship of each with age was examined and then the age-corrected scores of seven clinical groups were compared on each of these dimensions. The magnitude of the relationship between these dimensions and age was impressive and each dimension contributed unique information regarding these age-related changes. Moreover, the analysis of the clinical groups suggested that differential patterns of ventricular change were present dependent upon the disease. These results are discussed with a view to integrating the findings of previous studies and planning future studies.

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.

Computerized tomography findings among workers with chronic intoxication of the brain

Among the subjects classified as possibly or definitely demented 60% had suspected or definitely cerebral atrophy on CTs. Among the subjects classified as definitely demented 42% had definite cerebral atrophy. None of the referents had definite atrophy on CT. Regional cerebral blood flow was significantly decreased among subjects with cerebral atrophy. Some group overlap was evident as 12 subjects classified as definitely demented had normal CTs. This overlap showed that the absence of cerebral atrophy did not exclude the presence of dementia. On the other side, cerebral atrophy should not be found by a mere coincidence among persons under the age of sixty but indicates the presence of dementia.

Lesion size and recovery of function: some new perspectives

The present article discusses the possibility that functional recovery following brain damage may be to a large degree dependent on the amount of nervous tissue destroyed, such that more neuronal destruction may lead to more and not (as commonly suggested) to less recovery. This assumption may derive from the neuropsychological and neurological literature: many cases with circumscribed brain lesions are implicated with severe functional losses. However, patients with dramatic and severe brain destructions often show astonishingly normal behavior regarding cognition, speech, visuospatial, motor and sensory functions. Animal experimentation as well shows that an extensive lesion of a brain area may be associated with equal or less functional detriment than a small lesion of the same area. Along with the well-known variables of age, lesion growth, or personality and environmental factors, the amount of tissue destroyed should be considered as a potent mediator of functional recovery. At least for some functions and brain regions, the likeliness of recovery may increase with the extent of the lesion and thus the necessity of the brain to fulfill plastic changes.

Hypofrontality in schizophrenia: a review of the evidence

This paper reviews the possible role of frontal lobe dysfunction in the pathophysiology of schizophrenia. Pathological, computerized axial tomography (CAT) scan and magnetic resonance imaging (MRI) studies have indicated that a substantial number of schizophrenic patients show structural abnormalities in the frontal lobe areas and other parts of the brain. In some cases, these changes can be correlated with negative symptoms. Attempts to study frontal lobe function with neuropsychological tests, topographic EEG, cerebral blood flow (CBF) and positron emission tomography (PET) scans have also indicated that a substantial number of schizophrenics show abnormalities compared to normal controls. However, these abnormalities can be seen to some degree in other conditions. As well, patients early in the course of their illness tend not to show frontal lobe functional abnormalities. The implications of these findings for current theories of schizophrenia are discussed.

Quantitative X-ray computed tomography (CT) in dementia of the Alzheimer type (DAT)

Dementia of the Alzheimer type (DAT) has proven to be difficult to diagnose using computerized X-ray tomography (CT). To improve the identification of DAT with CT, several different quantitative approaches have been tried. Brain parenchymal density measurements and a variety of linear indices of ventricular size have failed to reliably separate DAT patients from age matched controls. Measures of ventricular volume improve discrimination, but overlap with controls persists. The inadequacy of a single CT study to diagnose DAT is clearly related to the overlap of brain atrophy in DAT and healthy aging, a finding which has also been noted in post-mortem studies. Estimating the rate of ventricular enlargement from quantitative measurements of ventricular size on successive CT scans may allow the physician to take advantage of the progressive nature of DAT, improving separation of DAT patients from healthy controls.

Brain imaging in functional mental disorders

The application of brain imaging techniques to psychiatry is reviewed with respect to computerized tomography (CT), EEG topography, positron emission tomography (PET), and magnetic resonance imaging (MRI). While early computerized tomography studies have suggested structural abnormalities in schizophrenia, more recent studies have shown that most schizophrenics and patients with other disorders have normal CT scans. EEG topography and positron emission tomography have not been evaluated as fully as computerized tomography. However, preliminary studies indicate some functional abnormalities in schizophrenia and affective disorders compared to normal controls. Magnetic resonance imaging shows promise but has had only a limited application to date in psychiatry.

Ventricle size, cortical atrophy and the relationship with neuropsychological status in closed head injury: a quantitative analysis

Forty-eight patients with a history of moderate to severe closed-head injury (CHI) were examined with neuropsychological measures and computerized tomography (CT). CT scans were assessed with computerized techniques to determine estimated ventricular volumes (VV) and the degree of cortical atrophy (ATVOL) in each patient. VV's then were used to determine volumetric ventricle-brain ratios (VBR) to correct for head size. The WAIS, Wechsler Memory Scale (WMS) and Halstead-Reitan Neuropsychological Test Battery (HRNTB) were administered to all patients. Correlational analyses were undertaken between VBR and ATVOL measures. PIQ but not VIQ was negatively correlated with VBR and ATVOL, particularly in terms of right-hemisphere measures. WMS Memory Quotient (MQ) also was negatively correlated with VBR and ATVOL with no lateralization. Several HRNTB measures similarly were correlated with ventricular and atrophy estimates. Correlational results also were analyzed in terms of the influence of higher and lower VBR and ATVOL, and the prior presence of hematoma. Results are discussed in terms of the latent effects of cerebral damage secondary to CHI on neuropsychological functioning.

Computed tomography in the elderly: changes over time in a normal population

The clinical, psychometric, and computed tomographic (CT) status of previously fit elderly volunteers is described at follow-up for up to four years. A number of relationships were found between psychometric and CT scores, but a dementing group could not be determined on the basis of a single scan. However, a subtle reduction in cognition over time was significantly related to CT changes, and occurred in 10%. Larger ventricles were also found in a small sub-group, who developed late-onset depressive disorders; recent bereavement was related to ventricular size. Thus a single CT scan may not be a useful discriminatory test in early dementia, but a repeat demonstrating ventricular enlargement, is likely to be significant. In the elderly, cognitive and CT scan deterioration should not be expected unless a disease process is occurring; this may be indicated by subtle cognitive impairment or by late-onset depressive disorder.

Computed tomographic brain studies and treatment response in schizophrenia

Ventricular enlargement has been described in chronic schizophrenia since 1927. The CT Scan has stimulated considerable interest and studies have shown that 50% of chronic schizophrenics and up to 20% of acute schizophrenics have enlarged ventricles. Widening of cortical sulci, cerebellar atrophy, third ventricular enlargement and reversed hemispheric asymmetry have also been reported. Ventricular enlargement seems to both predate the development of psychosis and to develop further during the course of the illness. Twin studies indicate that ventricular enlargement may be the result both of genetic vulnerability and of environmental onslaught. The other abnormalities may be secondary. Schizophrenics without ventricular enlargement show disturbances of a range of Dopamine-related variables. Schizophrenics with ventricular enlargement show some evidence of serotonin and noradrenaline cell loss. Very few published papers address the issue of treatment response. These seem to demonstrate a relationship between enlargement and poor response to neuroleptic medication. Schizophrenics with very large ventricles may also be particularly sensitive to the adverse effects of neuroleptics. It is not yet clear that the CT Scan may be used to identify patients unlikely to respond to medication. Long term prospective studies are required.

Normal pressure hydrocephalus: correlation between CT and measurements of cerebrospinal fluid dynamics

Twenty-nine patients consecutively admitted for consideration of CSF diversion surgery for suspected communicating ("normal pressure") hydrocephalus underwent cranial computerized tomography (CT) and study of cerebrospinal fluid (CSF) absorption, the latter determined as resistance to outflow of CSF (Ro). From the CT the size of the ventricular system was determined by various linear measurements and ratios and the presence of periventricular lucencies (PVL) and the size of cortical sulci was noted. Except for absence of cortical sulci greater than 3 mm no CT feature was suggestive of compromised CSF absorption. On the other hand, cortical atrophy did not rule out increased resistance to CSF-outflow. Features thought of as characteristic for normal pressure hydrocephalus on CT: large ventricles as compared with the amount of cortical atrophy and presence of PVL, correlated poorly with measured high resistance values. There was no correlation between the size of the ventricular system and resistance to CSF outflow. In the diagnostic distinction between communicating ("normal pressure") hydrocephalus and cerebral atrophy (hydrocephalus ex vacuo) static CT cannot replace an actual determination of CSF outflow resistance.

Quantifying cortical atrophy

Most of the methods of quantifying cortical atrophy that have been proposed involve the estimation of the volume of enlarged sulci in the cerebral cortex. The authors propose that the surface area of the sulci is a more valid measure of cortical atrophy, and describe a system for measuring the surface area of the cortex, and present data in support of the method's reliability and validity.

Partially reversible cerebral atrophy and functional improvement in recently abstinent alcoholics

52 recently abstinent chronic alcoholics were given repeated psychological tests and 20 of these had repeated CT scans. The first scan was done within 5 weeks of the last drink. The degree of measurably reversible cerebral atrophy on CT scan correlated negatively with the interval between the last drink and the first CT scan. Significantly more reversibility of cerebral atrophy was noted in those subjects claiming interscan abstinence. There were positive correlations between functional improvement scores on neurological exam and reversible cerebral atrophy measurements. Significant improvement on psychological test performance was restricted to patients tested initially within 3 weeks of the last drink. Both the CT results and the psychological test results suggest that reversible changes occur soon after the cessation of drinking.