Tailored TAPS via the Medial Optic-Tract Border for a Thalamomesencephalic Cavernoma.

Thalamomesencephalic cavernous malformations are rare deep lesions; anterior access is constrained by the optic apparatus, internal carotid artery, hypothalamus, oculomotor nerve, major white-matter pathways, and perforating vessels. We present a 51-year-old woman with a 25 × 27 × 31-mm hemorrhagic right thalamomesencephalic cavernous malformation, recurrent neurological exacerbations, left-sided weakness, and a left homonymous visual field defect. Through a right orbito-pterional craniotomy, the translamina terminalis, prechiasmatic, opticocarotid, and carotid-oculomotor corridors were sequentially assessed. None provided satisfactory access to the lesion center: they were non-coaxial, required transgression of normal hypothalamic or third ventricular tissue, or demanded excessive manipulation of the optic apparatus. Neuronavigation localized the nearest surface point to the medial border of the right optic tract and demonstrated that this trajectory was centered on the lesion and aligned with its long axis and mesencephalic component. A tailored transanterior perforated substance entry was therefore selected at this surface. We use frontopontine tract-hypothalamic interface (FPT-HI) as a case-specific descriptive term for the parenchymal relationship at the selected entry, not as a histologically validated plane or established safe-entry zone. No major visible perforator crossed the 6- to 8-mm fenestration, and the lesion was encountered after 2-3 mm of tissue. MRI at 1 week confirmed gross-total resection; at 3 months, no residual or recurrent lesion was seen and the homonymous defect improved substantially. At 5-year clinical follow-up, the patient remained asymptomatic. This case illustrates individualized corridor selection rather than a routinely applicable approach.