Objective. Central nervous system (CNS) involvement occurs frequently in systemic lupus erythematosus (SLE) and frequently results in morbidity. The primary pathophysiology of CNS involvement in SLE is thought to be inflammation secondary to autoantibody-mediated vasculitis. Neuroimaging studies have shown hypometabolism (representing impending cell failure) and atrophy (representing late-stage pathology), but not inflammation. The purpose of this study was to detect the presence and regional distribution of inflammation (hypermetabolism) and tissue failure, apoptosis, or atrophy (hypometabolism).
Methods. Eighty-five patients with newly diagnosed SLE, who had no focal neurologic symptoms, were studied. Disease activity was quantified using the Safety of Estrogens in Lupus Erythematosus: National Assessment version of the SLE Disease Activity Index (SELENA-SLEDAI), a validated index of SLE-related disease activity. 18 Fluorodeoxyglucose (FDG) positron emission tomography (PET) images of glucose uptake were analyzed by visual inspection and as group statistical parametric images, using the SELENA-SLEDAI score as the analysis regressor.
Results. SELENA-SLEDAI-correlated increases in glucose uptake were found throughout the white matter, most markedly in heavily myelinated tracts. SELENA-SLEDAI-correlated decreases were found in the frontal and parietal cortex, in a pattern similar to that seen during visual inspection and presented in previous reports of hypometabolism.
Conclusion. The SELENA-SLEDAI-correlated increases in glucose consumption are potential evidence of inflammation, consistent with prior reports of hypermetabolism in inflammatory disorders. To our knowledge, this is the first imaging-based evidence of SLEinduced CNS inflammation in an SLE inception cohort.
The dissociation among 18 FDG uptake characteristics, spatial distribution, and disease activity correlation is in accordance with the notion that glucose hypermetabolism and hypometabolism reflect fundamentally different aspects of the pathophysiology of SLE with CNS involvement.
Systemic lupus erythematosus (SLE), when present with central nervous system (CNS) symptoms, is characterized by a poorer prognosis, higher mortality rate (1), and reduced quality of life (2). The increased mortality and poor quality of life accompanying CNS involvement emphasize the importance of detecting SLE-mediated effects on the brain as early as possible. SLE, by best estimate, has a prevalence of ฯณ350,000 cases in the US (3), with CNS involvement in as many as 80% of those (2,4). Within the first 2 years of disease, ฯณ20% of patients report neuropsychiatric symptoms that are attributed to SLE (2). However, many patients (28-40%) report at least 1 neuropsychiatric episode before or during the first year after diagnosis (2).