Brain SPECT evaluation of amnestic ED patients after mild head trauma

A short period of amnesia is a common complaint after mild head injury. In this study we compare the duration of amnesia after mild head trauma to single photon emission computed tomography (SPECT) perfusion imaging shortly after admission to the emergency department (ED). Sixteen patients consecutively admitted to the ED were prospectively evaluated. The amnesia was scored according to the Extended Glasgow Coma Score. A computed tomography (CT) scan was performed to all patients. All patients had anterograde amnesia. Eleven patients had amnesia of grade 2 (69%) and 5 patients of grade 3 (31%). All patients had a normal CT scan. Twelve of sixteen patients (75%) showed regional perfusion abnormalities on the SPECT study. Decreased perfusion was observed at least in one region (8/12 patients had 2 abnormal regions). The logistic regression analysis showed that SPECT results significantly predicted the severity of amnesia (r = 0.9, P <.0001). Additionally, the SPECT accounted for approximately 84% of the variation in amnesia. We conclude that amnesia after mild head injury is associated with a high incidence of early regional cerebral perfusion abnormalities. Amnesia lasting more than half an hour is associated with bilateral cerebral hypoperfusion. SPECT evaluation in the ED may by a useful additional tool in the objective assessment of posttraumatic amnesia.