Vigabatrin-related MRI changes and tapering strategy in hemispherotomy for infantile spasms: illustrative case.

backgroundInfantile spasms associated with unilateral structural malformations represent a severe epileptic encephalopathy requiring early definitive treatment. Vigabatrin remains a first-line therapy, yet its reversible neurotoxic effects-linked to GABA-mediated intramyelinic edema-can produce MRI abnormalities that mimic disease progression. Differentiating these drug-related findings from true structural injury is essential when evaluating pharmacoresistance and determining the optimal timing for hemispherotomy. This illustrative case highlights these diagnostic challenges and proposes a practical approach to surgical decision-making and vigabatrin management. OBSERVATIONS: An 8-month-old boy with a right perinatal stroke developed persistent spasms despite adequate vigabatrin therapy. MRI revealed left-sided abnormalities involving the basal ganglia, optic pathways, and hippocampus, consistent with vigabatrin-induced intramyelinic edema. A right hemispherotomy resulted in immediate seizure cessation. Postoperative MRI changes remained clinically insignificant. Systemic toxicity prompted vigabatrin withdrawal, medication adjustments, and initiation of a ketogenic diet. Three months after surgery, MRI findings normalized, and the child remained seizure free. LESSONS: This case demonstrates that vigabatrin-related MRI abnormalities can closely mimic serious metabolic or vascular conditions, but are reversible and should not delay surgery when pharmacoresistance is established. Postoperative tapering can be safely implemented once seizure control is achieved, supporting timely intervention and avoiding unnecessary investigations. https://thejns.org/doi/10.3171/CASE26183.