Objective: The goal of this study was to determine the relative frequencies of benign external hydrocephalus (BEH), hydrocephalus and other conditions in a large series of imaging studies performed for macrocephaly and identify additional risk factors for patients with macrocephaly that would most likely benefit from neuroimaging evaluation.

Material and Methods: Medical records at our center were searched for the term macrocephaly retrospectively. The search extended from 1th January 2014 to 1th June 2019. Patients older than 36 months of age were excluded. Information about age, gender, symptoms and clinical signs (seizures, neurologic abnormalities on exam such as hypotonia), neuroimaging findings, developmental delay, family history of macrocephaly and head circumference (HC) were collected for each patient.

Results: A total of 103 patients were included in the analysis. The mean age at the time of imaging was 9 months (±5.5 months). Twenty-one (20.3%) of the subjects were female and 82 (79.6%) were male. Twenty-nine of the imaging studies were magnetic resonance imaging, 26 were computed tomography and 65 were head ultrasounds. Patients with abnormal neuroimaging results had significantly higher rates of developmental delay or abnormal neurologic exam than patients with normal neuroimaging results or BEH (p=0.003 and p<0.0001). There was no significant difference between the neuroimaging results of patients with and without positive family history of macrocephaly.

Conclusion: This study suggests that neuroimaging for macrocephaly has almost negligible diagnostic yield unless having developmental delay or abnormal neurological examination.

Keywords: Macrocephaly, benign external hydrocephalus, neuroimaging