The Prominent Subarachnoid Space in Children: How has a Normal Variant Become Medicolegally Life-Threatening Pathology?

A prominent subarachnoid space (SAS) in infants under 24 months is a very common finding and is a normal variant that can be associated with macrocephaly. This must be differentiated from various pathological conditions that also cause a prominent SAS, including a reduction in brain volume, obstruction to the cerebrospinal fluid (CSF) or malformations of the skull. The inappropriate labelling of normal SAS prominence as enlargement due to pathology and misrepresentation of published literature by some author groups has created confusion medicolegally, contributing to inappropriate conclusions that a normal prominent SAS may cause subdural haemorrhage (SDH) and brain injury. This paper aims to review the characteristics of the SAS in infants, the terminology relating to the prominence of the SAS and the possible association between the prominence of the SAS and SDH.