HMPAO single-photon emission computed tomography in posterior circulation infarcts

The sensitivity of single-photon emission computed tomography (SPECT) in evaluating posterior circulation infarcts compared with that of computed tomography (CT) or magnetic resonance imaging (MRI) remains unknown. In a hospital-based population, the authors studied SPECT, CT, and MRI in 35 consecutive patients presenting with acute infarction clinically localized in the thalamus (7), posterior cerebral artery (PCA) territory (15), brainstem (19), and cerebellum (3). Multiple infarcts were noted in 8 patients. Overall, the SPECT sensitivity was lower than that of MRI (21% vs 93%, p = 0.004) and CT (42% vs 65%, p = 0.046). The SPECT and CT sensitivities were not significantly different (67% vs 73%) for PCA infarcts. Performed within 24 hours, SPECT showed a relevant hypoperfusion in all PCA infarcts. For brainstem infarcts, CT (33%, p = 0.074) and MRI (91%, p = 0.004) were more sensitive than SPECT, which showed no hemispheric hypoperfusion. The sensitivity of the three imaging techniques was 100% for large cerebellar infarcts. For the small group of thalamic infarcts, the SPECT, CT, and MRI sensitivities were 14, 71, and 100%, respectively. Thus, SPECT compared to CT and MRI is not helpful in the subacute phase to localize PCA and cerebellar infarcts and is of limited value for thalamic infarcts. In the first hours, the absence of cerebral hypoperfusion in brainstem infarcts may help to differentiate them from hemispheric infarcts usually associated with profound hypoperfusion.