Abstract
BACKGROUND: Thalamic lesions located in the floor of the lateral ventricle pose significant surgical challenges, given their proximity to critical neurovascular structures. Transcortical approaches are often limited by risks of injuring the eloquent cortex and nearby vessels. Furthermore, lesions extending into the third ventricle further impede accessibility. The corticospinal tract (CST), situated close to the thalamus, presents a major obstacle. Diffusion tensor imaging plays a crucial role in overcoming these challenges by accurately delineating the CST's location relative to the lesion, enabling surgeons to plan minimally invasive and safe access. OBSERVATIONS: A 32-year-old female presented with progressive right-sided hemiparesis over several days. Magnetic resonance imaging revealed a cystic ring-enhancing thalamic lesion extending into the third ventricle. While supine, the patient underwent surgery via a right pericoronal parasagittal craniotomy followed by a contralateral interhemispheric transcallosal transchoroidal approach. LESSONS: This case exemplifies the utility of the contralateral interhemispheric transcallosal approach for treating thalamic lesions, particularly those extending into the third ventricle. This minimally invasive approach minimizes retraction of the eloquent cortex and reduces the risk of neurovascular injury, potentially leading to improved surgical outcomes and faster recovery.