Intracranial Hemorrhage Associated with Arachnoid Cysts

Arachnoid cysts (ACs) are often diagnosed incidentally, but they can become symptomatic due to hemorrhage. AC-associated hemorrhage (ACH) is rare, with a <0.1% annual hemorrhage risk for middle fossa ACs. There is often a preceding history of trauma, but many bleeding events are spontaneous. The most common pattern of hemorrhage is chronic subdural hematoma, but epidural hematoma and intracystic hemorrhage have also been described. Risk factors for ACH include head trauma, greater cyst diameter, and middle fossa location. Expectant management may be selected for small hematomas with minimal symptoms, while symptomatic hematomas with mass effect merit surgical evacuation with or without cyst fenestration. Surgical outcomes are favorable with low rates of hematoma recurrence. This chapter discusses the presentation, treatment, and outcomes of ACH and provides an illustrative case.