Diagnostic challenge of an arachnoid cyst mimicking hydatid cyst: a case report from Syria

Introduction: Cystic lesions in the brain, often seen in MRI and CT scans, may arise from various causes, including developmental issues, infections, or tumors. Differentiating between arachnoid cysts and hydatid cysts is critical for effective management, as misdiagnosis can lead to inappropriate treatments and worsen patient outcomes. Case presentation: An 18-year-old right-handed female from a rural area experienced a right-sided focal seizure lasting two minutes. Her history includes progressive right-hand pain, worsening writing difficulty, persistent headaches, personality changes, and recent memory impairment. She had slurred speech. Radiological examination revealed a massive cystic lesion in the brain which initially appeared to be a hydatid cyst, but histological examination revealed it to be an arachnoid cyst. Discussion: Arachnoid cysts, comprising about 1 % of intracranial masses, are commonly found fluid-filled sacs located in the arachnoid mater, usually incidentally discovered during imaging. They are more frequent in children and males, often asymptomatic but can cause symptoms based on their location. Classification includes congenital and traumatic types, with congenital being more common. Diagnosis can be challenging, especially when symptoms overlap with conditions like hydatid cysts, complicating treatment decisions. Conclusion: Arachnoid and hydatid cysts appear similar in surgery and may be hard to distinguish. Dissection difficulty should be the main way to differentiate them. A hydatid cyst diagnosis should not be ruled out until multiple attempts by an experienced surgeon have been made. Further studies are needed to clarify these findings.