Polyarteritis nodosa presenting as sixth nerve palsy: a case report.

Introduction: Polyarteritis nodosa (PAN) is a rare systemic necrotizing vasculitis affecting medium-sized vessels. While peripheral neuropathy occurs in 50-75% of patients, cranial nerve involvement is exceptionally rare, affecting fewer than 2% of patients. We report a case of PAN presenting with isolated sixth nerve palsy and orbital apex syndrome. Case presentation: A 70-year-old man presented with the acute onset of painful left abducens nerve palsy. His medical history included 3 months of constitutional symptoms, polyarthralgia, unintentional weight loss, and progressive hearing loss. Orbital MRI revealed enhancement extending from the left orbital apex through the superior orbital fissure to the cavernous sinus. During corticosteroid tapering, he developed painful cutaneous nodules, abdominal pain, and sensorimotor polyneuropathy with foot drop, fulfilling the diagnostic criteria for PAN. Treatment escalation with high-dose corticosteroids resulted in clinical improvement, with complete resolution of diplopia and stabilization of systemic manifestations at 6-month follow-up. Conclusion: This case highlights PAN as a rare but important cause of painful cranial neuropathy with orbital apex involvement. Clinicians should maintain a high index of suspicion for systemic vasculitis in patients presenting with painful ophthalmoplegia accompanied by constitutional symptoms, peripheral neuropathy, or cutaneous manifestations. Early recognition and prompt immunosuppressive therapy are essential to prevent irreversible neurologic damage and life-threatening complications.