Does I-131-MIBG underestimate skeletal disease burden in neuroblastoma?

BACKGROUND: Controversy persists as to the need for both MIBG and bone scanning in routine evaluation of neuroblastoma. AIM: To compare the efficacy of I-131- metaiodobenzylguanidine (MIBG) scan against that of conventional Tc99m- methylene diphosphonate (MDP) bone scan for the detection of skeletal deposition of neuroblastoma. METHODS AND MATERIAL: The study included 57 patients (36 boys, 21 girls: age range 1-14 years) of neuroblastoma who underwent both bone scan with Tc99m-MDP and I-131-MIBG scan within 15 days of each other at presentation and during follow-up. RESULTS: At presentation 11(19.2%) patients had evidence of skeletal metastases on MDP scan against 7 patients who showed bony secondaries on MIBG scan. Of the 7 patients, with positive MIBG and MDP scans, MDP scan detected 11 sites whereas MIBG scan detected 7 sites. On follow-up study, 3 patients with initial abnormal MDP scan but normal MIBG scan, developed skeletal metastases detectable on MIBG scan, whereas 3 of the 46 patients who had normal MDP and MIBG scan at presentation; developed skeletal metastases detectable on MDP scan. MIBG scan was concordant in 2 of them but was normal in the third patient. CONCLUSION: I-131-MIBG underestimates skeletal disease burden in neuroblastoma. Therefore, Tc99m-MDP bone scan should remain a part of routine assessment of patients with neuroblastoma.

Cerebellar medulloblastoma presenting with skeletal metastasis.

Medulloblastomas are highly malignant brain tumours, but only rarely produce skeletal metastases. No case of medulloblastoma has been documented to have produced skeletal metastases prior to craniotomy or shunt surgery. A 21-year-old male presented with pain in the hip and lower back with difficulty in walking of 3 months' duration. Signs of cerebellar dysfunction were present hence a diagnosis of cerebellar neoplasm or skeletal tuberculosis with cerebellar abscess formation was considered. MRI of brain revealed a lesion in the cerebellum suggestive of medulloblastoma. Bone scan revealed multiple sites of skeletal metastases excluding the lumbar vertebrae. MRI of lumbar spine and hip revealed metastases to all lumbar vertebrae and both hips. Computed tomography-guided biopsy was obtained from the L3 vertebra, which revealed metastatic deposits from medulloblastoma. Cerebrospinal fluid cytology showed the presence of medulloblastoma cells. A final diagnosis of cerebellar medulloblastoma with skeletal metastases was made. He underwent craniotomy and histopathology confirmed medulloblastoma.