Evidence of “regional hyperemia” in patients with severe closed head injury using single-photon emission computed tomography

Abstract

Regional cerebral blood flow (rCBF) was assessed in 32 patients with acute/subacute (n = 18) or chronic (n = 14) head injury using single-photon emission computed tomography (SPECT) and (99m)Tc-hexamethylpropylenenamine oxime (HMPAO) (n = 20) or (123)I-IMP (n = 12). Twelve of the 18 patients with acute/subacute head injury were studied with a high-resolution three-head camera and (99m)Tc-HMPAO. Twenty-eight SPECT studies showed regional abnormalities of tracer uptake. In all cases in which computed tomography (CT) and/or magnetic resonance imaging (MRI) (n = 30) were available for comparison, SPECT showed similar or more extensive abnormalities with high agreement on the laterality of the lesions. Particularly in the 18 patients with acute/subacute head injury, SPECT revealed more and larger lesions than the anatomical scans. In 9 of the 12 patients, at least one region with increase in HMPAO uptake reflecting "hyperemia" was detected (mean study time after injury, 6.3 ± 2.7 days). Follow-up SPECT scans in two patients showed decreased tracer uptake in the previous hyperemic regions and encephalomalacia in the anatomical scan. Thus, hyperemia may reflect "luxury perfusion" in early phases of head injury. In three patients with diffuse axonal injury, a generalized reduction in cortical tracer activity, especially in occipital/parietal regions, was observed. The typical finding in chronic head injury was observation of lesions of similar sizes and high agreement in focal abnormalities between SPECT and CT and/or MRI. However, in nine patients with behavioral disturbances, a decrease in the cortical/basal ganglia was detected. Thus, our study confirms the presence of hyperemia in acute/subacute head injury and demonstrates the value of SPECT for assessing functional impairment in these patients.