What is the condition called when two or more bones of the skull fuse prematurely?

The condition where two or more bones of the skull fuse prematurely is known as craniosynostosis. This occurs when the sutures of the skull close too early during an infant's development, affecting the normal growth of the skull and potentially leading to increased intracranial pressure or abnormal head shape. Timely diagnosis and intervention are crucial to managing this condition, as it may require surgical correction to allow for proper brain growth and to prevent any complications related to head shape and neurological development.

Other options relate to different conditions: hydrocephalus refers to an accumulation of cerebrospinal fluid within the brain's ventricles, microcephaly indicates a smaller than typical head size often associated with developmental issues, and exencephaly is a severe neural tube defect where brain tissue is located outside the skull. These conditions, while related to neurological development, do not pertain to the premature fusion of skull bones.