The Role of Aquaporin 1 in Water Retention Mechanism of Arachnoid Cysts: Insights from 3 Case Reports

Case series Patients: Male, 52-year-old • Male, 68-year-old • Female, 26-year-old Final Diagnosis: Arachnoid cyst Symptoms: Increased intracranial pressure Clinical Procedure: Pathology for surgical specimens Specialty: Neurosurgery • Pathology OBJECTIVE: Unknown etiology BACKGROUND: Although arachnoid cysts are common lesions, the pathogenesis of their continuous growth remains unclear. We aimed to identify the role of aquaporins in arachnoid cyst specimens. CASE REPORTS: We selected 3 cases from our own facility and examined arachnoid cyst wall specimens, which were sampled intraoperatively. Patients presented with variable symptoms, a 52-year-old man with a “heavy sensation” in the head and dysesthesia on the left hand, a 68-year-old man with unsteady gait, and finally a 26-year-old woman with a history of intermittent headaches for 10 years. Intraoperative specimens were obtained and examined. Evaluation techniques were light microscopy, immunohistochemical staining for aquaporin, and electron microscopy. Light microscopy showed that cells were arranged in epithelium-like structures forming several thick lamellae, with visible connective tissue among them. Under electron microscopic examination, cells with many or few cell organelles and with spindle-like nuclei were arranged in lamellar or flattened structures. Many vacuolizations were seen in between. Interdigitation of cells and many desmosomes were observed. All 3 cases were positive for aquaporin 1. CONCLUSIONS: Our study showed that water transportation through aquaporin 1 has a potential role in the formation and expansion of arachnoid cysts.