Complications Associated with an Extensively Pneumatized Skull Base: Systematic Review and Meta-Analysis

Introduction: Pneumatization patterns within the skull base and paranasal sinuses can vary between individuals. While pneumatization plays several protective roles, hyperpneumatization may lead to several complications, including cerebrospinal fluid (CSF) leaks, skull base fractures, and infections. To date there is no consensus that hyperpneumatization increases the risk for patient morbidity or increased postoperative or posttraumatic complications. We hypothesized that hyperpneumatization increases the risk of these complications. In order to address this clinical question, we performed a systematic review and meta-analysis of the relevant literature.

Methods: A systematic review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The search was conducted using PubMed/MEDLINE on April 29, 2023. The Patient, Intervention, Comparison and Outcome (PICO) criteria: patients with extensive pneumatization of the skull base, the measure of pneumatization degree, and complications including infection, fractures, or CSF leak. Exclusion criteria included purely anatomical studies, cadaveric studies, irrelevant anatomy, language other than English and case reports. A meta-analysis was performed using random effects model to assess the postoperative rates of CSF leak in hyperpneumatized versus nonpneumatized temporal bones.

Results: A total of 553 abstracts were initially identified and after application of inclusion and exclusion criteria, 34 articles were included in the final analysis. Qualitative synthesis identified CSF leak, infection, and skull-base fracture as the most common consequences of skull base hyperpneumatization. We analyzed spontaneous and postoperative complications separately. Retrospective cohort studies for spontaneous CSF leak showed significantly higher rates in hyperpneumatized sphenoid sinuses to the lateral recess. While multiple studies reported hypopneumatization of the mastoid air cells as protective against otitis media, a case series presented Luc’s abscess due to zygomatic air cells. Spontaneous temporal bone fractures were twice as likely in “very good” versus “poor” pneumatization of the mastoid (30.9% vs. 14.6%). In the setting of postoperative complications following transpetrosal, retrosigmoid, translabyrinthine, and middle cranial fossa approaches, there were significantly higher rates of CSF leak with petrous apex pneumatization compared to those without (20.8–25% vs. 0–13.8%). The pooled results demonstrated a similar finding with significant increase in rates of CSF leaks in patients with pneumatized petrous apex (OR, 3.05; 95% CI, 1.62–5.72).

Conclusions: This is the first systematic review assessing the degree of skull base pneumatization and spontaneous or perioperative complications. Traditionally, pneumatization was viewed favorably for middle ear disease and temporal bone fractures due to improved air exchange and energy absorbing capacity. However, unusually hyperpneumatized spaces provide a conduit for infectious propagation to the skull base and leads to structural instability. Additionally, preoperative recognition of petrous bone pneumatization is critical. Traditional air cell packing with fat or muscle tissue is not sufficient to prevent CSF leak from petrous bone hyperpneumatization due to intraoperative “blind spots.” More studies are warranted to address this clinical question.