Safe reoperation for a newly developed brainstem cavernoma in a different region after prior resection.

Background: Brainstem cavernous malformations (BSCMs) may occur as multiple lesions, each capable of producing new neurological symptoms on hemorrhage. To date, there have been no reports of surgical intervention for a new hemorrhage occurring in a different region of the brainstem in patients with a prior history of BSCM resection. Case Description: A woman in her 60s presented with progressive gait instability and right lower limb weakness. Thirteen years earlier, she underwent aneurysm clipping and ventriculoperitoneal shunting for subarachnoid hemorrhage, during which multiple intracranial cavernomas were incidentally identified. She later suffered a pontine hemorrhage managed conservatively (9 years prior) and a right pontomedullary hemorrhage requiring resection through a lateral suboccipital approach (7 years prior). Two years ago, a new hemorrhage at the left pontomesencephalic junction was initially asymptomatic but subsequently enlarged, causing worsening ataxia and right hemiparesis. Resection was performed through a left subtemporal approach, guided by fiber tractography, neuronavigation, and multimodal intraoperative neuromonitoring (including motor-evoked potentials). Complete excision was achieved without new neurological deficits, and the patient regained independent ambulation. Conclusion: Even after prior brainstem surgery, subsequent resections of newly developed cavernomas in distinct locations can be performed safely. Detailed preoperative planning with tractography and rigorous intraoperative monitoring are pivotal in minimizing surgical risk and optimizing outcomes.