Ultrasonographic Assessment of Subarachnoid Space Dimensions in Healthy Infants: Normative Data for the First Three Months of Life

Background The subarachnoid space is a clinically important anatomical region among various pathologies including subdural effusions, hydrocephalus, and benign enlargement of the subarachnoid space. Therefore, accurate measurement regarding subarachnoid space dimensions is necessary in terms of early diagnosis as well as clinical follow-up. Reference data remain limited and show variability among ethnic and geographical groups although several studies reported normative values for subarachnoid space width in different populations. Up until now, there are no ultrasonography-based normative data that have been established in relation to either age or sex. Head circumference (HC) and Z-scores for body weight (BW), body height (BH), body mass index (BMI), and body surface area (BSA) are applicable during the first three months of life. Objective To establish ultrasonography-based normative reference values for subarachnoid space width in healthy infants during the first three months of life. Materials and methods A total of 125 infants aged 0 to 3 months underwent cranial ultrasound examinations. Subarachnoid space measurements—including craniocortical width (CCW), sinocortical width (SCW), interhemispheric width (IHW), and cisterna magna width (CMW)—were assessed. These measurements were compared with infants’ age, HC, and Z-scores for BW, BH, BMI, and BSA. Age-specific 5th, 50th, and 95th percentiles of the subarachnoid spaces were generated. Independent determinants in subarachnoid space width were identified through linear regression analysis. Results The mean CCW and SCW were 1.72 ± 0.67 mm (range, 0.70–4.40) and 2.45 ± 0.78 mm (range, 0.90–4.90), respectively. The mean IHW and CMW were 2.37 ± 0.94 mm (range, 0.50–5.10) and 3.38 ± 1.23 mm (range, 1.20–6.80), respectively. All subarachnoid space measurements increased significantly with age. CCW and SCW were significantly associated with the Z-scores for BW, BMI, and BSA, while HC was positively correlated with IHW and CMW. Linear regression analysis revealed that age was the only independent predictor of CCW and SCW, whereas both age and HC significantly predicted CMW. Conclusion We report the first national ultrasound-based normative data for subarachnoid space width in healthy infants aged 0–3 months, which may serve as a valuable reference in routine pediatric practice.