Post-operative neurologic outcomes in children with WNT-medulloblastoma.

e22005 Background: WNT-activated medulloblastoma (WNT-MB), the least common molecular subtype of medulloblastoma with a putative brainstem cell of origin, is associated with excellent survival outcomes. Recent clinical trials have focused on decreasing morbidity related to craniospinal irradiation and chemotherapy. Little is known about the role of surgery in contributing to long-term morbidity in this population. Objective: To describe the incidence and persistence of post-operative neurologic morbidity in patients with WNT-MB. Methods: We conducted a retrospective cohort study of pediatric patients with molecularly confirmed WNT-MB who underwent tumor resection and treatment at our institution between 2003–2024. Demographic, clinical, treatment, and neurologic outcome data were extracted. Neurologic findings were assessed pre-operatively, post-operatively prior to the initiation of radiation or chemotherapy, and at last follow-up. Changes in functional neurologic exam domains and posterior fossa syndrome symptoms were analyzed. Results: One hundred sixty-four patients with medulloblastoma who had available molecular subgroup data were identified; 16 (10%) had WNT-activated tumors of whom 13 met study inclusion criteria. The median age at diagnosis was 9 years (range 5-16). Median follow-up time was 8 years (range 0.6-16.1). One patient died early in their treatment course; the remaining 12 patients (92%) were alive at last follow-up. New post-operative neurologic deficits were seen in all 13 patients (100%), most commonly involving loss of independent ambulation (n=12, 92%), motor function (n = 11, 85%), language (n=10, 77%), and cranial nerve abnormalities (n= 8, 62%). Post-operative posterior fossa symptoms were frequent, including dysarthria (n=10, 77%) and ataxia (n=9, 69%). Ten patients (77%) exhibited persistent deficits at last follow-up. Conclusions: Despite excellent overall survival, patients with WNT-MB experience notable post-operative neurologic morbidity. More conservative resection strategies should be considered in future prospective studies for this population.