- Etiology: due to immature + inefficient arachnoid villi causing immature CSF resorption leading causing temporary communicating hydrocephalus
- Imaging: subarachnoid space relatively larger in infants < 2 years old, subarachnoid vessels cross the space, can appear asymmetric in patients who also have plagiocephaly
- DDX: chronic subdural hematomas – note that patients with chronic subdural hematomas do not present with macrocephaly alone
- Clinical: presents with macrocephaly, most common cause of macrocephaly, resolves on its own by 2 years
Radiology Cases of Benign Enlargement of the Subarachnoid Space
