A widened subarachnoid space might be pathologic, potentially pathologic, or simply a normal developmental variant. However, the definition of a normal subarachnoid space width in infants remains unclear, especially on computed tomography (CT) images. To determine the physiological subarachnoid space width among infants aged 1-24 months, its upper limit, and changes with age, we measured the cerebrospinal fluid width on 538 CT images. Measurements were obtained at fixed planes and fixed positions to prevent variance and increase comparability between patients. We observed an asymmetry in the cerebrospinal fluid width of the temporal region. The width increased in all positions until 4-6 months of age, after which it began to decrease, reaching a relatively stable range in infants aged 13-24 months. We suggest considering the 95th percentile of the cerebrospinal fluid width as the upper limit. The correlation between age and the subarachnoid space width should be considered during clinical diagnosing.
Keywords: CSF width; benign external hydrocephalus; pediatrics; subarachnoid space.