PROTON MAGNETIC-RESONANCE SPECTROSCOPY AND GADOLINIUM-DTPA PERFUSION IMAGING OF ASYMPTOMATIC MRI WHITE-MATTER LESIONS

In the elderly, asymptomatic white matter hyperintensities are common on T-2-weighted magnetic resonance imaging (MRI). In symptomatic patients, such MRI appearances correlate with varied postmortem findings including demyelination or stroke. What structural correlates underlie the T-2 hyperintensities in patients whose lesions are asymptomatic is controversial. Therefore, in order to investigate the underlying metabolism and perfusion in white matter lesions (exhibiting T-2 hyperintensity), 13 patients underwent proton magnetic resonance spectroscopy and dynamic gadolinium-DTPA perfusion-weighted MR imaging. N-acetyl aspartate (NA) levels were reduced in the lesions compared with age-matched controls (P = 0.031), implying neuronal/axonal loss, Creatine levels were also reduced (P = 0.001). Choline levels were unchanged in the lesions. Lactate was identified in the lesions of 5 of the 13 patients. Although not statistically significant, perfusion studies exhibited a trend toward lower cerebral blood volumes in patients with high grade extracranial carotid stenosis and lactate-containing lesions, These findings suggest that neuronal/axonal loss underlies the majority of T-2-weighted asymptomatic lesions in the older population, and in many cases these changes may be due to chronic ischemia.