Objective: Benign expansion of the subarachnoid spaces (BESS) is a condition seen in macrocephalic infants. BESS is associated with mild developmental delays which tend to resolve within a few years. It is accepted that patients with BESS are at increased risk of spontaneous subdural hematomas (SDHs), although the exact pathophysiology is not well understood. The prevalence of spontaneous SDH in BESS patients is poorly defined, with only a few large single-center series published. In this study the authors aimed to better define BESS prevalence and developmental outcomes through the longitudinal review of a large cohort of BESS patients.
Methods: A large retrospective review was performed at a single institution from 1995 to 2020 for patients 2 years of age or younger with a diagnosis of BESS by neurology or neurosurgery and head circumference > 85th percentile. Demographic data, head circumference, presence of developmental delay, occurrence of SDH, and need for surgery were extracted from patient charts. The subarachnoid space (SAS) size was measured from the available MR images, and the sizes of those who did and did not develop SDH were compared.
Results: Free text search revealed BESS mentioned within the medical records of 1410 of 2.6 million patients. After exclusion criteria, 480 patients remained eligible for the study. Thirty-two percent (n = 154) of patients were diagnosed with developmental delay, most commonly gross motor delay (53%). Gross motor delay resolved in 86% of patients at a mean age of 22.2 months. The prevalence of spontaneous SDH in this BESS population over a period of 25 years was 8.1%. There was no significant association between SAS size and SDH formation.
Conclusions: This study represents results for one of the largest cohorts of patients with BESS at a single institution. Gross motor delay was the most common developmental delay diagnosed, and a majority of patients had resolution of their delay. These data support that children with BESS have a higher prevalence of SDH than the general pediatric population, although SAS size was not significantly associated with SDH development.
Keywords: benign expansion of the subarachnoid spaces; benign external hydrocephalus; cerebrospinal fluid; head circumference; motor development; subdural hematoma; trauma.