Cranial nerve deficit caused by skull metastasis of prostate cancer: three Japanese castration-resistant prostate cancer cases.

We report 3 Japanese patients with cranial nerve deficit caused by skull metastasis of prostate cancer (PCa). Case 1 was a 75-year-old patient with a chief complaint of diplopia. The cause of diplopia was right oculomotor nerve palsy from the skull metastasis. External beam radiation therapy (EBRT) to the whole brain, 40 Gy in 20 fractions, was performed and the diplopia improved. Case 2 was a 72-year-old patient with a chief complaint of facioplegia. Bone scintigraphy and computed tomography (CT) of the head revealed right occipital bone metastasis of PCa resulting in right facial nerve palsy. EBRT to the right occipital bone, 50 Gy in 25 fractions, with daily oral dexamethasone (DEX) was performed and facioplegia showed complete recovery. At 12 months after onset, the patient was followed-up with no symptoms. Case 3 was a 74-year-old patient with a chief complaint of diplopia. Diffusion-weighted magnetic resonance imaging (MRI) and positron emission tomography (PET) showed right petrous bone metastasis resulting in right abducent nerve palsy. EBRT to the right petrous bone, 44 Gy in 22 fractions, with oral DEX was performed and diplopia showed complete recovery. At 13 months after onset, the patient was followed-up with no symptoms. MRI and PET may detect PCa metastasis in the skull base more clearly than other imaging modalities. EBRT with 40-50 Gy in 20-25 fractions in association with corticosteroid administration may be reasonable treatment of patients with metastatic PCa who develop cranial nerve dysfunction.