Role of positron emission tomography in determining the extent of CNS ischemia in patients with sickle cell disease

Nearly 25% of patients with sickle cell disease (SCD) experience central ne rvous system morbidity involving both large and small vessel disease. Optim al imaging methods for determining the extent of ischemia are not known. Po sitron emission tomography (PET) has the unique ability to show tissue func tion as well as structure. Reports concerning patients with non-SCD neurode generative disorders suggest PET may be useful in determining prognosis. We compared magnetic resonance imaging, magnetic resonance angiography, and n europsychological testing with PET prospectively. Six patients with SCD and a history of stroke, aged 10 to 28, were enrolled. PET studies were perfor med on an ECAT HR 47 scanner (Siemens/CTI, Knoxville, TN) using 18-F-fluoro deoxyglucose as a tracer. PET interpretations were conducted in blinded fas hion. MRI studies found two patients with only small vessel disease and fou r with both large and small vessel disease. In two of four subjects with la rge vessel disease, PET showed a corresponding metabolic abnormality and al so identified an area of hypometabolism extending beyond the anatomical les ion as shown by MRI. PET did not demonstrate an abnormality corresponding w ith small vessel disease. Detailed neuropsychological testing demonstrated cognitive dysfunction in all cases. For some patients, PET may add sensitiv ity in detecting impaired metabolism in the area surrounding a major vessel infarct. However, the technique does not appear to be generally useful in characterizing smalt watershed or deep white matter infarcts. Larger studie s, to include control subjects and carefully selected un-transfused SCD pat ients, are needed. A combination of conventional imaging and neuropsycholog ical testing remains the preferred evaluation for most SCD patients with ne urologic symptoms. Am. J. Hematol. 60:268-272, 1999. 1999 Wiley-Liss,Inc.