Clinical utility of computed tomography in the assessment of dementia: a memory clinic study

Objective: To define the influence of computed tomography (CT) on clinical decision-making in the outpatient evaluation of dementia.

Design: A case series in which two physicians reviewed standardised data extracted from clinical records, first blind to CT results, and then with CT results. Clinical decisions made with and without the input of CT were compared. The study was based in an outpatient referral centre for the assessment of memory disorders and dementia. The study involved 146 participants who were diagnosed with dementia after their first clinic visit, had Mini Mental State Examination scores >12, were aged >65 years, and had no history of neurologic disease.

Results: CT impacted on diagnosis in an average of 12% (+/-2), and on treatment plan in 11% (+/-2) of cases. Physicians predicted a priori which cases CT may influence with an average sensitivity of 28% (+/-2), and specificity of 78.5% (+/-1.5). There was no statistically significant relationship between diagnostically uncertain cases and helpful CT scans [average chi(2) = 1.121 (+/-1.116), p = ns]. Blind to CT physicians appropriately identified cerebrovascular disease with an average sensitivity of 63% (+/-3), and specificity of 93.5% (+/-3.5).

Conclusions: In the outpatient setting, CT may be expected to impact on diagnosis and treatment of dementia in 10% to 15% of cases. Memory clinic physicians recognise and treat cerebrovascular risk factors with reasonable sensitivity and specificity without the input of CT.