Retro-Odontoid Calcium Pyrophosphate Deposition Pseudotumor Presenting with Isolated Hypoglossal Nerve Palsy: A Case...

Introduction Retro-odontoid pseudotumor is a rare non-neoplastic lesion of the craniocervical junction, most commonly associated with inflammatory or degenerative conditions. Calcium pyrophosphate deposition (CPPD) disease is an underrecognized cause. Cranial nerve involvement is uncommon, and isolated hypoglossal nerve palsy is exceedingly rare. Case Report We report a 75-year-old woman who presented with a 5-month history of occipital headache followed by acute onset of left hypoglossal nerve palsy. Imaging revealed a partially calcified retro-odontoid mass extending toward the left hypoglossal canal. Laboratory and rheumatologic investigations were unremarkable. The patient underwent posterior C1-C2 fusion with biopsy. Histopathology confirmed CPPD disease. At 6-month follow-up, magnetic resonance imaging (MRI) demonstrated significant regression of the lesion accompanied by clinical improvement. Conclusion This case highlights that posterior stabilization alone may provide effective indirect decompression and promote lesion regression while avoiding more invasive anterior approaches.