To report a rare case of intracranial calcium pyrophosphate deposition disease (CPPD) with cranial neuropathy and cervical cord compression, manifesting as a retro-odontoid pseudotumor with craniocervical junction involvement.

CPPD is a crystal arthropathy predominantly causing pseudogout in peripheral joints. Intracranial involvement at the craniocervical junction and skull base represents an exceptionally rare manifestation with <100 cases reported. CPPD pathophysiology involves calcium pyrophosphate dihydrate crystal deposition forming mass-like pannus tissue that can mimic neoplastic or infectious processes. Early recognition is crucial as this can cause progressive neurological deterioration and requires management distinct from other etiologies.

This case report includes neurological examination, imaging, rheumatological serologies, and clinical response assessment to corticosteroid therapy with serial imaging follow-up.

An 85-year-old male with hypertension, diabetes mellitus, hyperlipidemia, and COPD presented with acute-onset diplopia preceded by episodic left-sided headaches and isolated left abducens nerve palsy. CTA revealed an extra-axial mass at the craniocervical junction displacing the proximal basilar artery posteriorly with severe spinal canal stenosis at C1 causing cord compression. MRI excluded acute ischemia, confirming a T2-hypointense extra-axial retro-odontoid mass consistent with chronic pannus formation. Rheumatological serologies showed mildly elevated ESR (24), normal CRP, and negative rheumatoid factor, yielding low suspicion for active inflammatory arthropathy. Diagnosis was established from characteristic imaging findings in the absence of histopathological confirmation. Patient’s symptoms persisted despite empiric prednisone 60mgQD. Interval MRI demonstrated mild progressive mass enlargement consistent with CPPD-related chronic retro-odontoid pseudotumor with new intracranial extension. Patient referred for neurosurgical evaluation upon discharge.

This case underscores intracranial CPPD as a critical differential for extra-axial skull base masses, particularly in elderly patients. CPPD at the craniocervical junction can cause cranial neuropathies and myelopathy through mass effect and vascular compression. Recognition of characteristic imaging features in the absence of tissue confirmation is crucial for accurate diagnosis and avoiding delayed or unnecessary interventions.