The main conventional treatment modalities for cSDH include drilling and drainage, craniotomy hematoma removal, etc. Compared with conventional treatment modalities, MMA embolization for cSDH has been reported to be associated with lower recurrence rates and a lower incidence of in-hospital complications1 2 5-7. Ironside et al.5 included data from 20 studies for meta-analysis and reported that the rates of cSDH recurrence in the MMA embolization group was 4.8% (95% CI 3.2% to 6.5%) , and the rates of cSDH recurrence in the conventional management group was 21.5% (0.6% to 42.4%). Compared with the conventional management group, MMA embolization was associated with a lower recurrence rate (OR=0.15, 95% CI 0.03 to 0.75, p=0.02) . In spite of the improvements in treatment modalities, recurrence remains complex and poorly understood. We report a rare case of cSDH in which burr-hole craniostomy and drainage combined with MMA embolization was performed, followed by neovascularization of the contralateral MMA that crossed the midline to supply blood to the hematoma, which led to recurrence. At the initial DSA, we did not observe radiological findings that showed that the opposite MMA supply to the hematoma. The subsequent recurrence of the hematoma led to a second craniotomy combined with contralateral MMA embolization. During the second DSA, the effect of the original MMA embolization was found to be satisfactory. Surprisingly, we found that a new vascular network developed from the contralateral MMA that supplied the hematoma. Continuous CT scans after the first treatment (3, 5, and 7 days after surgery) revealed the presence of irregular high-density shadows and continuous enlargement of the hematoma, possibly indicating that the new blood vessels in the MMA on the opposite side of the hematoma continued to supply blood to the hematoma. This rare clinical discovery may help in the understanding of the potential mechanism of cSDH recurrence.
The formation, expansion, and recurrence of cSDHs involve complex pathological and physiological processes, such as sustained and complex inflammatory reactions, unstable angiogenesis of the outer membrane, abnormal coagulation function, and abnormal fibrinolysis2 3 5 6. Fully understanding the mechanism of cSDH formation, development, and recurrence will help clinicians find safer and more effective treatment modalities4-6 8. Therefore, some therapeutic drugs discovered based on their pathological and physiological characteristics include glucocorticoid drugs (such as dexamethasone), statin drugs (such as atorvastatin), and antifibrinolytic drugs (such as tranexamic acid)3 9. Angiogenesis of the outer hematoma membrane is a critical factor for the formation, expansion, and recurrence of CSDH1 3 4. The release of angiogenic factors and inflammatory mediators may lead to angiogenesis, increased vascular wall permeability, and increased hematoma volume1 3. MMA embolization can block the blood supply in the hematoma and reduce the release of inflammatory mediators, promoting hematoma absorption and resolution. In this study, even if no positive expression was detected in the contralateral MMA during the first DSA, radiological manifestations of neovascularization of the contralateral MMA progressing toward the hematoma side were still observed during subsequent development. It might indicate that the progression of CSDH which is known to be an angiogenic and inflammatory process also exists in the contralateral MMA. Hubbard et al.10 have also reported that similarly rare recurrence due to contralateral neovascularization after MMA embolization for the cSDH. Unexceptionally, due to limitations imposed by the small sample size, the generalizability is affected. In addition, contralateral external carotid artery (ECA) angiography alone was not performed during the first procedure. Hence, blood supplied to the cSDH by the contralateral ECA at the first DSA cannot be ruled out. This may suggest that selective DSA of the contralateral MMA of the lesion and selective embolization of the contralateral MMA with positive radiological findings (such as “cotton wool like” changes) are proper treatment options and methods for reducing the rate of cSDH recurrence.