Organizing posterior fossa hematomas simulating developmental cysts on prenatal imaging: report of 3 cases.

OBJECTIVE: We encountered 3 organizing tentorial hematomas simulating posterior fossa lesions such as Dandy-Walker, dermoid, or arachnoid cysts. We sought to correlate the clinical and pathologic features that allow distinction of developmental cysts from hematomas in the posterior fossa on imaging. METHODS. Prenatal sonograms in all fetuses and fetal magnetic resonance scans in 2 of the 3 were reviewed. One case proceeding to term had serial imaging up to age 11 months. Two cases had complete neuropathologic evaluation after termination. Maternal records were reviewed.
RESULTS: In each case, the ultrasonographic findings were reminiscent of a developmental cyst but with echogenic debris, a rim, or both. Magnetic resonance imaging suggested tentorial hemorrhage in 2, 1 also with falcine hemorrhage. Serial prenatal and postnatal imaging showed resolution in the surviving case. Pathologically, 2 fetuses had organizing tentorial hematomas causing brain displacement. Calcifications, white matter damage, germinal matrix hemorrhage, and brain stem necrosis were also present. One mother had von Willebrand disease.
CONCLUSIONS: Tentorial hematomas, with or without maternal coagulopathy, should be considered in the prenatal ultrasonographic diagnosis of cystlike posterior fossa abnormalities containing echogenic material. Fetal magnetic resonance imaging can suggest blood products. Hypoxic-ischemic brain damage may be concurrent; however, resolution of the hematoma, with no apparent neurologic sequelae, can occur.