Diagnostic yield of cerebral imaging in patients with acute confusion

Acute confusion (AC) is a frequent reason for hospital admission in elderly patients. Although in majority of cases the cause is a systemic disorder (e.g., dehydration or septicaemia), patients are frequently subjected to cerebral imaging. This study was undertaken to find clinical predictors of normal cerebral computed tomography (CCT) or magnetic resonance imaging (MRI) scans in AC.

Retrospective study of 294 patients admitted with AC of unknown origin, of whom 178 received cerebral imaging.

The rate of pathological imaging studies was 14%. The best single predictor of a normal brain scan was the absence of focal signs. Patients without focal abnormalities and either fever or dehydration had a probability of 0.96 of having a normal CCT or MRI. In demented patients without focal signs, the predictive value for a normal brain scan was 0.98, and if either patients with drowsiness were excluded or the existence of fever or dehydration was added as a selection criterion, all patients had normal scans.

Patients with AC without focal signs and with either evidence for a medical aetiology of delirium or prediagnosed dementia are at a very low risk of having focal lesions in their CCT or MRI.