Letter: Middle Meningeal Artery Embolization for Primary Treatment of a Chronic Subdural Hematoma in a Pediatric Patient: A Systematic Review of the Literature and Case Report.

Abstract

To the Editor: We read with great interest the recent publication by Paro et al1 highlighting the emergence of endovascular middle meningeal artery (MMA) embolization as a less invasive addition to the neurosurgical armamentarium to treat pediatric chronic subdural hematoma (cSDH). Based on their case report and review of 5 published cases, this technique appears to be safe and effective in the appropriately selected pediatric patient. We would like to highlight 3 considerations that will better inform us in the future which pediatric patients would benefit the most from this approach. The first consideration is pediatric age. The brain volume, cranial vault volume, and expected growth of each in an infant are vastly different to that of an adolescent. The close match of brain volume relative to the cranial volume is likely sufficient in older children and adolescents to eliminate potential space for formation of a hygroma or cSDH. In infants, if there is not a persistent mechanism for poor brain development, the brain growth may actually be a significant driver of head growth, and any contemporary mismatch that creates a potential space may be expected to resolve. This may be similar to benign natural history of extra-axial fluid of infancy.2 In these cases, MMA embolization may be less useful. These expectations for children may not hold true if there is an underlying mechanism for brain volume loss or poor brain development; this could be observed with chronic disease (as is sometimes seen in congenital cardiac disease or oncologic pathology) or severe injury (such as hypoxic injury or severe nonaccidental injury). Most of these alternative scenarios where there is an increased risk of persistent brain to cranial volume mismatch happen in infants. As such, MMA embolization may be more relevant to this age group within the pediatric demographic. The second consideration is cSDH etiology. In their paper, Paro et al1 reported that 2 of 6 cSDH cases treated by MMA embolization occurred in the setting of ruptured arachnoid cysts. It is noted that in the absence of neurological decline, resolution of these pediatric cSDHs can occur with conservative management.3 Even in the presence of symptoms, medications such as acetazolamide have been shown to promote cSDH resorption in pediatric patients after arachnoid cyst rupture.4 These reports indicate that MMA embolization should not be seen as the least invasive management option for all pediatric cSDH cases upfront. However, other etiologies such as trauma and spontaneous formation may be more amenable to MMA embolization as a lesser invasive, more permanent procedure compared with subdural taps, subdural drains, and burr hole evacuation options.5,6 The last consideration is ideal timing. It is currently unclear when MMA embolization is most effective in pediatric patients with cSDH given the natural history. Parameters to consider include hematoma size and suspicion for cSDH recurrence. We hypothesize that larger hematoma size and recurrent cSDH could be less amenable to MMA embolization. This would then question whether or not MMA embolization should be performed as first-line treatment for smaller cSDHs on initial presentation. This speculation, however, must be balanced against the potential of pediatric cSDH to self-resolve with time, as well as the need to avoid anesthetic and procedural risks as much as possible. Larger, prospective studies in the pediatric demographic are needed to better understand this. It remains challenging to understand the clinical application of MMA embolization in children when diverse populations (infants to adolescents) with different pathologies (ruptured arachnoid cyst, abusive head trauma, and unknown mechanism) are intermixed. In sum, Paro et al1 highlighted the emergence of MMA embolization to treat pediatric cSDH. There is more than likely a place in the pediatric niche for this technique, and more research is required to better identify those pediatric patients who will benefit from this intervention the most. Considerations should be given for pediatric age, cSDH etiology, and intervention timing.