Chronic Subdural Hematomas Associated with Arachnoid Cysts: Significance in Young Patients with Chronic Subdural Hematomas.

Although arachnoid cysts (ACs) are associated with chronic subdural hematomas (CSDHs), especially in young patients, the detailed features of CSDHs associated with ACs remain poorly understood. The objective of this study was to clarify the relationship between the location of CSDHs and ACs and the significance of ACs in young patients with CSDHs. We retrospectively assessed 605 consecutive patients 7 years of age and older who were diagnosed with a CSDH between 2002 and 2014. Twelve patients (2%) had ACs, and 10 of the 12 patients were 7-40 years of age. Patients with ACs as a complication of CSDHs were significantly younger than those without ACs (p < 0.05). Three different relationships between the location of CSDHs and ACs were found: a CSDH contacting an AC, an ipsilateral CSDH apart from an AC, and a CSDH contralateral to an AC. In 21 patients with CSDHs who were 7-40 years of age, 10 (47.6%) had ACs (AC group) and 7 (33.3%) had no associated illnesses (non-AC group). All 10 young patients with ACs showed ipsilateral CSDHs including a CSDH apart from an AC. All 17 patients in both the AC and non-AC groups showed headache but no paresis at admission. The pathogenesis of CSDHs associated with ACs may be different among the three types of locations. The clinical characteristics of patients with a combination of a CSDH and an AC including headache as a major symptom may be attributed to young age in the majority of patients with ACs.