Computed Tomography in the Investigation of Dementia

Abstract

To assess the value of computed tomography in investigating patients with dementia, 500 consecutive patients presenting with a provisional clinical diagnosis of dementia of recent onset were reviewed and the results analysed in a computer. Most patients had either cerebral atrophy or infarction, but 82 patients had a normal scan and 42 others had tumours. More than 10% of all patients, including 5% with no other symptoms or signs, had a treatable lesion. Various associated symptoms and signs were useful pointers to such a treatable lesion and clearly indicated computed tomography. Accurate diagnosis is the cornerstone of proper management, and if a few patients with treatable lesions can be identified then the benefits to all concerned may be incalculable.focal signs. But the presentation is seldom so clear cut.4 The term "multi-infarct dementia" is preferred to indicate the association with hypertension or extracerebral vascular disease, or both, rather than "atherosclerosis," which implies disease of the small intracerebral vessels.6 Many other less common causes of dementia have been quoted, including alcoholism, Huntington's chorea, depression, normal pressure hydrocephalus, hypothyroidism, anaemia, liver disease, colloid cyst, and intracranial tumours.7 8Clearly, it may be difficult to differentiate those possible causes clinically. Nevertheless, an accurate diagnosis is essential, both for managing the patient and for informing the family, as this may have serious implications for them and economic consequences for the State. Computed tomography of the head may be regarded as one part of the diagnostic range, particularly for younger patients and for those with a recent onset of dementia. At Frenchay Hospital we have been accepting such patients from hospital consultants in the south-west region since our scanner was installed in 1974. Almost 10% of new patients for computed tomography are referred with a provisional diagnosis of dementia. MethodsThe clinical features and brain scan findings were reviewed in 500 consecutive patients referred to this neuroradiological unit for investigation of dementia over 18 months. Patients with predominantly psychotic features were excluded. We accept requests for

Systematic Review of Clinical Prediction Rules for Neuroimaging in the Evaluation of Dementia

“…Of the 57 articles obtained for in-depth review, 7 met eligibility criteria for inclusion in this analysis 13,14,16,17,[20][21][22][23][28][29][30][31] (Table 2). One study evaluated 4 different prediction rules with the use of the same patient population, 13 whereas another study compared 2 prediction rules in the same patient population.…”

“…Each study examined a consecutive series of patients with dementia who were referred to a dementia clinic 13,16,17,22 or to a radiology unit 20,28 ; the total number of patients undergoing evaluation per study ranged from 98 to 500 (Table 2). The overall frequency of potentially reversible causes of dementia detectable by neuroimaging was lower in patient populations drawn from dementia and geriatric clinics (0%-3.9%) compared with studies where patients were identified from radiology units (6.5%-10.4%).…”

“…†The published background paper for the AAN guideline cited studies 13,[20][21][22] and an editorial. 23…”

“…3 Early detection of normal pressure hydrocephalus or subdural hematomas is more likely to improve outcomes after surgery compared with patients with tumors causing dementia. 3,20,29,44 Further studies evaluating the impact of neuroimaging on physicians' management decisions and on patient outcomes are needed to evaluate the role neuroimaging has in the evaluation of dementia.…”

Isolated dementia in two patients with posterior intraventricular meningiomas

“…0.6% among all secondary dementias) (David, 1988;Howell, 1988). Most "tumoural" cases have presentations that easily distinguish them from typical Alzheimer's disease; thus, several authors have proposed strategies for a selective approach to imaging in dementia, mainly based on observations drawn from the clinical history and the physical examination of the patient (Bradshaw et al, 1983;Dietch, 1983; seems reasonable to advance the proposal for a further revision of this decision rule: we suggest that relatively young patients (less than 70 years of age) should always undergo "routine" neuroimaging when cognitive impairment is documented and is not explained by metabolic factors or drugs, irrespective of the duration of cognitive impairment at the time of presentation. A duration of less than 1 year could be advocated for older people.…”