Local glucose metabolism is unaltered in reversible splenial lesion syndrome

Abstract Background and purpose Transient splenial oedema, also known as reversible splenial lesion syndrome (RESLES), is a rare magnetic resonance imaging (MRI) finding that presents as a round or ovoid focal oedema in the posterior corpus callosum, and is associated with a wide range of clinical conditions. The aetiology of RESLES is not fully clear. We aimed to investigate conflicting pathophysiological hypotheses by measuring local glucose metabolism in patients with RESLES. Methods We retrospectively analysed patients with RESLES after reductions in antiseizure medications during in‐hospital video electroencephalography monitoring. We measured local glucose uptake using positron emission tomography/computed tomography and compared matched cohorts of patients with and without MRI evidence of RESLES using nonparametric tests. Results Local glucose metabolism in the splenium of seven patients with RESLES was not significantly different from the glucose metabolism of the seven patients in the matched cohort. This was true using both regular and normalized standardized glucose uptake value calculation methods ( p = 0.902 and p = 0.535, respectively). Conclusion We found no evidence of local glucose hypometabolism in RESLES, which supports previous pathophysiological considerations that suggest that RESLES is an intercellular, intramyelinic oedema rather than a typical intracellular cytotoxic oedema, which is not reversible.