Radiologic Characteristics and Clinical Correlates of Quadrigeminal Cistern Arachnoid Cysts: A Retrospective Study.

Introduction Quadrigeminal cistern arachnoid cysts (QACs) represent a rare subgroup of arachnoid cysts. Patients may present with headache, visual disturbances, gait imbalance, or nausea, typically secondary to obstructive hydrocephalus. Hydrocephalus is frequently assessed using the Evans Index (EI). Vertebral artery hypoplasia (VAH) is generally defined as a decrease in the diameter of the vertebral artery. It has been associated with posterior circulation ischemia, vertebrobasilar insufficiency (VBI), vertigo, and headache. However, the relationship between QAC-related mass effect and vascular variants such as VAH has not been systematically evaluated. Mega cisterna magna (MCM) represents another posterior fossa cerebrospinal fluid variant relevant to the differential diagnosis. Objective To evaluate the relationship between QAC dimensions, EI, vertebral artery diameters, and clinical symptoms, and to assess the coexistence of MCM. Methods Seventy-three patients (36 females, 37 males; mean age 52.4 ± 19.0 years) with radiologically confirmed QAC were retrospectively reviewed. Clinical symptoms, including headache and VBI, were recorded. Imaging parameters included QAC anteroposterior (AP) diameter, quadrigeminal cistern diameter, EI, vertebral artery diameters, and the presence of MCM. Multivariable logistic regression analysis was performed to identify imaging predictors of clinical symptoms (odds ratio (OR) and confidence interval (CI)). Results Headache was present in 67.1% of patients, VBI in 31.5%, and MCM in 21.9%. Mean QAC AP diameter was 16.9 ± 4.8 mm, quadrigeminal cistern diameter 23.1 ± 5.2 mm, and EI 0.24 ± 0.08. Mean right and left vertebral artery diameters were 2.46 ± 0.83 mm and 2.36 ± 0.73 mm, respectively. Headache showed no independent association with any imaging parameter (p-value > 0.05). VBI was significantly associated with a smaller left vertebral artery diameter (OR 0.32; 95% CI 0.16-0.64; p-value = 0.001). Conclusion In patients with QAC, headache did not correlate with radiologic measurements, whereas VBI was strongly associated with reduced vertebral artery diameter, particularly on the left side. These findings highlight the importance of incorporating vascular assessment when evaluating symptomatic QAC patients.