Hydatid cyst of the neck presenting with left upper limb paresthesia in a 29-year-old man: a case report.

Background: Hydatid disease (echinococcosis) is a parasitic infection caused by Echinococcus species, commonly involving the liver and lungs. Cervical hydatid cysts are exceptionally rare, even in endemic regions, accounting for less than 1% of cases. Clinical presentation often mimics other benign neck masses, making early diagnosis challenging. Neurological manifestations due to mass effect on neural structures are exceedingly uncommon.

Case presentation: We report a rare case of a 29-year-old Iranian man presenting with a 2-week history of progressive left-sided neck swelling and associated paresthesia in the left upper limb. Physical examination revealed a firm, mobile mass in the left posterior triangle of the neck. Neurological examination showed decreased sensation in the C5-C6 dermatome. Imaging studies revealed a simple cystic lesion adjacent to the left carotid sheath. Surgical excision confirmed a hydatid cyst compressing the brachial plexus. Histopathology supported the diagnosis. The patient experienced full resolution of neurological symptoms within 2 months postoperatively, and no recurrence was noted at 1-year follow-up. Albendazole therapy was continued for 2 months post-surgery.

Conclusion: To our knowledge this is the second documented case of a cervical hydatid cyst presenting with neurological symptoms due to brachial plexus compression. It underscores the importance of considering hydatid disease in the differential diagnosis of neck masses, particularly in endemic areas or among individuals with livestock exposure. Prompt surgical intervention combined with antiparasitic therapy is essential for a favorable outcome.