Natural History of Chronic Subdural Hematoma Following Middle Meningeal Artery Embolization: A Retrospective Analysis

Objective: The efficacy of middle meningeal artery (MMA) embolization in the management of chronic subdural hematoma (cSDH) has been increasingly supported by recent randomized controlled trials. However, long-term data on the natural history of cSDH post-treatment remain limited. This study aims to evaluate the natural history and outcomes of cSDH over a 12-month period following MMA embolization.

Methods: We conducted a retrospective analysis of 61 MMA embolization for the treatment of cSDH in 49 consecutive patients at a single institution between October 2019 and December 2022. Patients underwent MMA embolization as the primary treatment of cSDH, concurrently with surgical evacuation, or after initial surgical evacuation and subsequent recurrence. Clinical data, including patient demographics, hematoma maximal thickness, midline shift size, procedural details, and outcomes, were collected and analyzed. The primary outcomes assessed were time to resolution of hematoma maximal thickness, midline shift reduction and clinical improvement. Secondary outcomes included occurrence of complications, recurrence rate, and the characteristics of the group of patients who needed surgical rescue. Tables and Kaplan-Meier curves were created, broken down by the percentage of reduction in current hematoma maximal thickness. Results for the primary, concurrent, and recurrent groups were compared.

Results: The mean age of the patients included was 73 ± 10.8 years. Among them, 33 patients (67.3%) reported a history of previous trauma, with falls being the main mechanism of injury (65.3%). The majority of patients (77.5%) were male. The most frequent neurological symptom was headache (61.2%). The mean hematoma thickness and midline shift were 15.9 ± 7.1 and 5.6 ± 2.6 mm, respectively. There was a significant improvement in clinical symptoms within 1 month following MMA embolization. Kaplan-Meier curves were generated for resolution of hematoma size and midline shift. At 1 month postprocedure, only 25% of patients had at least a 25% reduction in hematoma size. However, by 3 months, 75% had a decrease in hematoma size by 50%. About 85% of patients had complete resolution of hematoma by 7 months, and all patients had resolution of hematoma by 12 months. Four patients underwent surgical rescue hematoma evacuation and the mean timeframe between the embolization and the surgical rescue was 2 weeks. Hematoma size and midline shift resolved faster for patients who underwent concurrent or rescue surgical evacuation of hematoma in addition to embolization. No difference in results between the liquid embolics N-butyl cyanoacrylate and Onyx-18 was found.

Conclusions: This study demonstrated a favorable resolution of subdural hematoma within 7 months in 85% of patients and in all patients by 12 months. By 3 months, 50% of patients had a decrease in hematoma size by 50% or more. A complete resolution of midline shift within 7 months, and a significant improvement in clinical symptoms within 1 month following MMA embolization. Hematoma size and midline shift resolved faster for patients who underwent embolization for recurrent hematoma or concurrent surgical evacuation of the hematoma in addition to embolization.