Advances in diagnosis and management of chronic subdural hematoma

Chronic subdural hematoma (CSDH) is one of the most common neurosurgical conditions, particularly among the elderly, with an annual incidence ranging from 1.7 to 20.6 per 100,000 people. As the global population ages and the use of antiplatelet and anticoagulant therapies increases, the incidence of CSDH is projected to rise significantly. Despite its clinical prevalence, treatment options have seen limited breakthroughs over the past two decades, largely due to an incomplete understanding of its pathophysiology. This review provides a comprehensive overview of the epidemiology, pathogenesis, diagnostic approaches, and evolving treatment strategies for CSDH, with a special focus on the emerging role of middle meningeal artery embolization (MMAE).

Epidemiology of CSDH

CSDH is the second most common neurosurgical disease and is especially prevalent in the elderly, with rates as high as 127.1 per 100,000 among those over 80 years old. The increasing use of anticoagulant and antiplatelet medications, combined with a higher risk of falls in the aging population, contributes to its growing burden. By 2030, CSDH is expected to surpass brain tumors as the most frequent condition in cranial surgery. Recurrence remains a significant challenge, affecting approximately 10% of surgically treated patients, with risk factors including advanced age, anticoagulant use, male gender, and poor postoperative brain re-expansion.

Etiology and pathogenesis

The development of CSDH involves a complex interplay of traumatic, inflammatory, and angiogenic mechanisms. While traditional models emphasized bridging vein rupture, recent biomechanical studies suggest this may not fully explain non-traumatic cases. Instead, current evidence highlights the role of dural border cell layer injury, leading to inflammation, fibrinolytic dysregulation, and neovascularization. Key mediators such as vascular endothelial growth factor (VEGF) and pro-inflammatory cytokines (e.g., IL-6, IL-8) drive membrane formation and recurrent microbleeds from fragile neovessels. This self-perpetuating cycle of inflammation and angiogenesis underpins the chronicity and recurrence of CSDH.

Radiographic diagnosis

Computed tomography (CT) remains the primary imaging modality for CSDH, typically revealing hypodense, isodense, or mixed-density crescentic collections. However, CT has limitations in detecting small or isodense hematomas and in characterizing internal architecture. Magnetic resonance imaging (MRI) offers superior soft-tissue resolution, enabling better visualization of septations and membrane structures, which can help predict recurrence risk. Advanced MRI techniques, including diffusion-weighted imaging, are increasingly used to assess hematoma maturity and guide treatment planning.

Treatment of CSDH

Surgical Interventions

Surgery is the mainstay for symptomatic CSDH or cases with significant mass effect. Common techniques include:

• Twist-drill craniostomy (TDC): Minimally invasive, bedside-appropriate, but associated with higher recurrence and risks of cortical injury.

• Burr-hole craniostomy (BHC): The most widely used method, with high efficacy and low morbidity, though recurrence remains a concern. Technical variations-such as irrigation fluid type, patient positioning, and drainage location (subdural vs. subgaleal)-are areas of ongoing debate.

• Craniotomy: Reserved for complex, recurrent, or organized hematomas, but carries higher complication and mortality rates.

• Endoscopic-assisted evacuation: Allows direct visualization and complete membrane removal, potentially reducing recurrence, though it requires expertise and may prolong operative time.

Middle Meningeal Artery Embolization (MMAE)

MMAE has emerged as a promising minimally invasive intervention that targets the neovascularization responsible for CSDH persistence and recurrence. By embolizing the middle meningeal artery, blood supply to the hematoma membranes is reduced, promoting resolution. MMAE can be used as a primary treatment or as an adjuvant to surgery, particularly in high-risk patients, such as those on anticoagulants or with recurrent CSDH. Studies report recurrence rates as low as 4.3% with MMAE, though its role in acute symptom relief remains limited.

Non-surgical and pharmacological management

For asymptomatic or high-risk patients, conservative management is an option. Pharmacologic therapies aim to modulate inflammation and angiogenesis:

• Atorvastatin: Reduces inflammation and promotes vascular repair, showing promise in reducing hematoma volume and recurrence.

• Corticosteroids: Potent anti-inflammatory agents, but evidence of efficacy is mixed, and long-term use carries significant side effects.

• Tranexamic acid (TXA): An antifibrinolytic agent that may reduce rebleeding, though its safety in elderly patients requires further study.

• ACE Inhibitors: Controversial due to conflicting data on their effect on angiogenesis and recurrence.

• Herbal Medicine: Preliminary studies suggest agents like Goreisan may reduce recurrence, though clinical evidence remains limited.

Future directions

Despite advances, CSDH management is hampered by a lack of standardized protocols and limited high-quality evidence. Future efforts should focus on:

• Clarifying pathophysiological mechanisms to enable targeted therapies.

• Validating the efficacy and safety of MMAE through randomized trials.

• Developing consensus on surgical techniques and perioperative care.

• Exploring combination therapies, such as statins with corticosteroids or MMAE with minimally invasive surgery.

Conclusion

CSDH is a dynamically evolving field in neurosurgery. While surgical evacuation remains the cornerstone of treatment, recurrence and complication rates underscore the need for improved strategies. MMAE represents a paradigm shift, offering a targeted, minimally invasive alternative. Pharmacological interventions and enhanced imaging techniques further enrich the therapeutic landscape. Future research must prioritize mechanistic insights and multidisciplinary collaboration to optimize outcomes for this increasingly prevalent condition.