Paradoxical hyperfixation of hexamethylpropyleneamine oxime in cerebral infarction

We describe four patients with cerebral infarction and 99mTc-hexamethylpropyleneamine oxime (HMPAO) hyperfixation in distributions corresponding to the infarctions seen at CT and/or MR imaging. Increased HMPAO extraction due to hyperpermeability across the blood-brain barrier and increased retention due to reduced back diffusion of the tracer probably accounted for the increased fractional fixation in infarcts seen in our patients.