Benign enlargement of the subarachnoid spaces in infancy (BESS) also known as benign external hydrocephalus (BEH), a benign enlargement of subarachnoid spaces seen in infancy. It is characterized clinically by macrocephaly or frontal bossing.

It usually occurs in males than females. It has familial predilection.  The condition resolves spontaneously by the age of 2 years.