Background and Importance: Plasma Cell Dyscrasias (PCD) are a heterogeneous group of diseases having a spectrum from multiple myeloma to solitary plasmacytoma, a rare subtype, which constitutes 2 to 5% of all PCD. It typically involves axial bones but the involvement of skull bone is very rare.
Case Presentation: We are reporting a case of inion bony lesion with venous sinus infiltration in a 55-year-old male patient, presented with pain, imbalance in walking, and swelling in the occipital region. Brain MRI suggested an extra-axial lesion with skull involvement and venous sinus infiltration. The tumor was infiltrating into the sinus with patent torcular venous confluence. Tumor decompression followed by radiosurgery of residual lesion was considered in pre-operative surgical planning. It was diagnosed as a case of myeloma cell disease on histopathology. Postoperative myeloma work-up confirmed the absence of any systemic involvement. The patient was given a course of radiotherapy.
Conclusion: One-year follow-up with repeated MRI and myeloma investigations in the 3rd month, 6th months, and 1 year did not show any finding suggestive of progression to multiple myeloma. The follow-up of brain MRI showed a complete resolution of the residual tumor.