RESUMO
BACKGROUND: Local hemostatic agents have been used in the neurosurgical field for many years; it is safe and efficient with no fatal complication reported in the literature. We routinely used a gelatin-thrombin hemostatic agent (FloSeal Hemostatic Matrix) for hemostasis in minimally invasive endoscopic-assisted surgery for more than 500 patients with intracerebral hemorrhage. However, 2 cases with sterile cyst formation were encountered. CASE DESCRIPTION: We reported 2 cases with sterile cyst formation after the use of a gelatin-thrombin hemostatic agent. Both of them had intracerebral hemorrhage. One received endoscopic hematoma evacuation, and the other had traditional craniotomy. They all received drainage of the cyst due to progressive enlargement and the mass effect they exert. CONCLUSIONS: These sterile cysts were very close to the ventricle wall on images. We hypothesized that cyst wall may be formed not only by hemostatic agent-related fibrosis and inflammation according to the previous literature review but also by the presence of the check valve mechanism between the cyst and the ventricle, which caused further dilation of the cyst.