Evaluation of Association of Prematurity with Benign Enlargement of Subarachnoid Space in Infants Referred for Macrocephaly.

Introduction: Benign enlargement of subarachnoid space (BESS) is one of the causes of macrocephaly in infants. The aetiology of this condition remains a subject of controversy, with poor cerebrospinal fluid absorption as the most commonly believed underlying theory. Prematurity has been suggested as possible risk factor; however, this is a topic of debate with paucity of data. In this study, we investigated association of prematurity with BESS in our cohort of patients.

Methods: A retrospective review of patients seen in outpatient neurosurgical BESS clinic (period 2016-2023) was carried out. BESS was defined as enlarged frontal subarachnoid space diagnosed on CT or MRI brain obtained for macrocephaly. Demographics information including sex, age, prematurity/gestation at birth, grade of prematurity as well as any neurosurgical interventions were recorded. Prematurity was defined as per World Health Organization guidelines as birth at gestation<37 weeks. Grade of prematurity was defined as <28 weeks as extreme preterm, 28-32 weeks as severe preterm, 32-34 weeks as moderate preterm, and 34-37 weeks as late preterm.

Results: Over the period of study, 100 children with BESS were seen in the outpatient clinic setting with mean age of 12.3 months (range 0.5-54 months) with M78:F22 ratio (M:F = 3.5:1). Overall, 19 out of 100 children with BESS were born premature (19%) with a mean age of 11.9 months at diagnosis. Premature group included 0% extreme preterm, 21% severe preterm, 15.8% moderate preterm, and 63.2% late preterm. Rate of prematurity at 19% in this cohort was 2.4-fold the rate of UK prematurity of 7.5-7.9% (p = 0.023). Eight out of 100 (8%) patients had concurrent subdural collection of which one belonged to premature group. All subdural collections were managed non-operatively. There was no association between prematurity and subdural formation. No child required cerebrospinal fluid diversion.

Conclusion: BESS remains a poorly understood entity. Considering the baseline rate of live preterm births in UK at 7.5-7.9%, rate of prematurity in this cohort of children was significantly higher at 19%. This study may support that prematurity is a possible risk factor.