Suboccipital transhorizontal fissure approach for a deep-seated pediatric cerebellar tumor: illustrative case.

BACKGROUND: Surgical access to deep cerebellar lesions near the upper fourth ventricle and dentate nucleus is challenging because conventional transcortical or transvermian routes may injure the normal cerebellar cortex, white matter, or cerebellar output pathways. The suboccipital transhorizontal fissure approach (SOTHF) uses the cerebellar horizontal fissure as a natural corridor and may reduce approach-related cerebellar injury. OBSERVATIONS: An 11-year-old boy presented with vertigo and had a small enhancing lesion with surrounding FLAIR hyperintensity approximately 25 mm beneath the cerebellar surface in the deep cerebellar hemisphere near the fourth ventricle. Because the lesion was adjacent to the brainstem and dentate nucleus and intraoperative frozen-section diagnosis could guide additional resection, an intermediate SOTHF approach was selected rather than stereotactic biopsy. Dissection of the horizontal fissure allowed access to the lesion with minimal disruption of the cerebellar cortex and white matter. Frozen-section analysis showed no high-grade features, and the procedure was limited to diagnostic sampling. The patient recovered uneventfully, was discharged home on postoperative day 12 with a modified Rankin Scale score of 0 and remained neurologically intact at 6 months. LESSONS: SOTHF may provide a function-preserving surgical corridor for selected pediatric deep cerebellar lesions by minimizing injury to the normal cerebellar parenchyma. https://thejns.org/doi/10.3171/CASE26504.