Title: A rare Presentation of Reversible Splenial Lesional Syndrome (RESLES) in a case of Idiopathic Intracranial Hypertension (IIH)

Transient focal lesions of the splenium of the corpus callosum (SCC), known as reversible splenial lesion syndrome (RESLES), have been linked to diverse etiologies such as infection, metabolic disturbances (e.g., hypoglycemia, hyponatremia), seizure activity, antiepileptic drug withdrawal, ischemia, and trauma but rarely described with IIH. These lesions typically present as ovoid areas of restricted diffusion and T2/FLAIR hyperintensity in the midline splenium, resolving spontaneously within days to weeks, without residual deficit.

Case:

The present case demonstrates a 62-year-old woman with typical clinical ( 2 weeks of headache with right sided papilledema, BL abducens nerve palsy, opening pressure of 56cm H20) and imaging features of IIH(prominent optic nerve sheaths with protrusion and enhancement of the optic nerve heads as well as flattening of the posterior aspect of the globes bilaterally) who also exhibited a transient splenial lesion, a finding rarely associated with IIH. Her initial MRI revealed a small focus of diffusion restriction and T2/FLAIR hyperintensity in the posterior midline SCC, which completely resolved within three weeks following CSF drainage and acetazolamide therapy, consistent with RESLES.

Our findings suggest that RESLES may occasionally arise as a reversible response to severe intracranial hypertension, reflecting transient metabolic stress rather than irreversible tissue injury. This case underscores a rare but noteworthy radiologic finding in IIH.