Long-term control of primary brainstem tumors with MRI-guided laser interstitial thermal therapy: illustrative cases

BACKGROUND Brainstem tumors are difficult to treat because of their deep location and proximity to eloquent structures. Gross-total resection is rarely feasible and carries substantial risk. MRI-guided laser interstitial thermal therapy (MRgLITT) offers a minimally invasive alternative in select cases, but long-term outcomes have not been reported. OBSERVATIONS The authors retrospectively reviewed the cases of 2 patients with primary brainstem tumors treated with MRgLITT. One patient underwent mural nodule ablation following cyst aspiration via a right frontal trajectory for a large cystic pontine pilocytic astrocytoma (WHO grade 1). The other patient underwent ablation via a left frontal trajectory followed by external-beam radiation therapy (59.4 Gy in 33 fractions) for a dorsal midbrain ependymoma (WHO grade 3). Both patients experienced improvement in preoperative symptoms without new deficits. Empiric dexamethasone (4 mg every 8 hours, tapered over 3 days) was used postoperatively. At the last follow-up (9 and 10 years, respectively), neither patient demonstrated radiographic recurrence. LESSONS MRgLITT can provide durable tumor control in carefully selected primary brainstem tumors when meticulous trajectory planning, thermal monitoring, and adjunctive therapies such as radiation therapy, when appropriate, are used. Avoiding overablation, managing cystic components, and anticipating postablation transient edema are critical to minimize morbidity. https://thejns.org/doi/10.3171/CASE26273