Object. Benign extracerebral fluid collections are common in infants, but there are unanswered questions regarding presentation and long-term outcome. This study was undertaken to establish head size at birth, head size at presentation, head growth over time, history of presentation, indications for surgery, and long-term results. Methods. Cases of benign extracerebral fluid collections in infancy were retrospectively reviewed. Data pertaining to clinical presentation, progress, and long-term follow-up were evaluated. Patients were divided into two groups on the basis of the presence or absence of increased signal intensity of fluid in the extracerebral space on T1 -weighted magnetic resonance images. Group 1 consisted of 39 patients who had benign extracerebral fluid collections without any subdural collections. Group 2 consisted of nine patients who had a chronic subdural hematoma or hygroma without a history of trauma and had generous subarachnoid spaces and/or a history of premature birth. Patients were observed for an average of 49 months. Results. Group 1 included 39 patients (ages at presentation 3-12 months); the most common presentation in this group was macrocephaly (28 cases). Of those Group 1 cases in which data regarding gestational age at birth were available, 15 births were either severely or mildly premature and 14. were full term. Of those Group 1 patients with adequate data, 14 had an occipitofrontal circumference (OFC) in the 50th to 98th percentile at birth and two had OFCs greater than the 98th percentile. Measurements obtained at 24 months of age were available for 18 Group 1 patients: OFC was at approximately the 98th percentile in eight (all eight born at full term) and more than 1 cm larger than the 98th percentile in 10. Head growth in Group 1 patients continued to decrease, approaching the 98th percentile after 24 months of age. Only three of the 39 patients in Group 1 required shunt placement. Of the 33 Group 1 patients for whom longterm follow-up was available, 30 were developing normally, and three had mild developmental delays. Group 2 included nine patients (ages at presentation 3-7 months); the most common presentations were large head (three patients) and seizures (three patients). Data concerning gestational age at birth were available in eight Group 2 cases: birth was severely premature in four and gestation was full term in four. Five Group 2 patients were treated surgically-two with subduroperitoneal (SDP) shunt placement, two with subdural punctures, and one with subdural punctures and SDP shunt placement. Adequate follow-up information was available in eight of nine Group 2 cases; all eight patients were found to be developing normally. Conclusions. Group 1 patients usually had a normal head size at birth, they rarely required shunt placement, their head growth eventually leveled off toward the 981 percentile line, and their outcomes were generally good. Although five of nine Group 2 patients required subdural punctures and/or SDP shunt placement, that group of patients also developed well. Infants with nontraumatic subdural hematomas or hygromas, presumably associated with benign extracerebral fluid collections, can often experience significant resolutions of the hematoma or hygroma within several months without surgical treatment.
