Hypercalcemia associated with relapsed medulloblastoma due to bone metastasis: illustrative case.

backgroundMedulloblastoma can cause extraneural metastasis, particularly to the bones. However, only a few reports have shown that hypercalcemia occurs with medulloblastoma, and there are no reports on hypercalcemia causing consciousness disturbance. OBSERVATIONS: A 17-year-old male patient was treated for medulloblastoma with spinal and intracranial metastasis. He underwent subtotal resection, followed by radiotherapy to the craniospinal axis, posterior fossa, and primary site, as well as high-dose chemotherapy with autologous hematopoietic stem cell transplantation. He achieved complete remission after the initial treatment. However, 30 months after tumor resection, he developed headache, nausea, fatigue, and pain in the limbs and back, followed by consciousness disturbance. He had severe hypercalcemia (17.7 mg/dL) and multiple bone metastases. His symptoms improved with hypercalcemia treatment, and salvage chemotherapy resulted in complete remission of the recurrent disease. LESSONS: Previous studies have not reported consciousness disturbance caused by hypercalcemia due to medulloblastoma bone metastasis. Hypercalcemia causes various symptoms, affecting the neurological, cardiac, and gastrointestinal systems. Some of its symptoms, such as fatigue, nausea, vomiting, and bradycardia, are similar to those of increased intracranial pressure. Therefore, hypercalcemia attributed to bone metastases should be considered in the differential diagnosis of consciousness disturbance during the course of medulloblastoma. https://thejns.org/doi/10.3171/CASE25318.