REVERSIBLE CEREBRAL HYPOPERFUSION IN LYME ENCEPHALOPATHY

Lyme encephalopathy (LE) presents with subtle neuropsychiatric symptom s months to years after onset of infection with Borrelia burgdorferi. Brain magnetic resonance images are usually normal. We asked whether q uantitative single photon emission computed tomography (SPECT) is a us eful method to diagnose LE, to measure the response to antibiotic ther apy, and to determine its neuroanatomic basis. In 13 patients with obj ective evidence of LE, SPECT demonstrated reduced cerebral perfusion ( mean perfusion defect index [PDI] = 255), particularly in frontal subc ortical and cortical regions. Six months after treatment with 1 month of intravenous ceftriaxone, perfusion significantly improved in all 13 patients (mean PDI = 188). In nine patients with neuropsychiatric sym ptoms following Lyme disease, but without objective abnormalities (e.g ., possible LE), perfusion was similar to that of the treated LE group (mean PDI = 198); six possible LE patients (67%) had already received ceftriaxone prior to our evaluation. Perfusion was significantly lowe r in patients with LE and possible LE than in 26 normal subjects (mean PDI = 136), but 4 normal subjects (15%) had low perfusion in the LE r ange. We conclude that LE patients have hypoperfusion of frontal subco rtical and cortical structures that is partially reversed after ceftri axone therapy. However, SPECT cannot be used alone to diagnose LE or d etermine the presence of active CNS infection.