Chronic subdural hematoma (CSDH) is one of the most common diseases in neurosurgery. An externally injured patient’s head is inflicted with chronic intracranial hemorrhage that occurs 3 weeks after externally inflicting the injury on the dura mater and arachnoid. With the gradual increase in the amount of hematoma, the surrounding brain tissue is pushed and compressed, resulting in corresponding clinical symptoms and signs [ 1 ]. The manifestations of CSDH are diverse, mainly due to the immediate compression of the intracranial area due to hematoma expansion. The common symptoms of this disease include headache, epilepsy, changes in mental state, weakness, sensory disorders, dysarthria, gait disorders, nausea and vomiting, stroke, and coma [ 2 ]. It is reported that the overall incidence rate of CSDH is 1.72 to 20.6 per 100,000 people every year, and the incidence rate of the elderly is particularly high [ 3 ]. With the aging population and the increasing use of anticoagulants and antiplatelet drugs, as well as the development of imaging, CSDH has become increasingly common worldwide. It is estimated that by 2025, it may become the most common neurosurgery disease [ 4 ].

Although chronic subdural hematoma is a common disease in neurosurgery, its treatment and management are still controversial. Regarding the treatment of CSDH, traditional treatment methods mainly include conservative (observation or medication) treatment and surgical treatment, and the specific treatment method mainly depends on the patient’s hematoma volume, symptoms, and signs; patients with small amount of hematoma and mild symptoms generally choose conservative management, while patients with large amount of hematoma and symptoms generally use surgical treatment represented by drilling and drainage. These traditional treatment methods are considered to be simple and safe. However, regardless of the treatment method, CSDH patients have a certain recurrence rate after treatment. According to literature reports, the recurrence rate can be as high as 10-30% [ 5 ]. After the recurrence of hematoma, many patients require multiple hospitalizations or even surgeries, leading to more complications. There are many pathological factors that lead to the recurrence of CSDH after treatment, including inflammation around the hematoma and the newly formed high permeability capillaries in the outer membrane of the hematoma confirmed by histology [ 6 , 7 , 8 ]. What complicates the management of CSDH patients is that the main incidence group of CSDH is the elderly, who often have multiple underlying diseases. Therefore, many of them require the use of antiplatelet and anticoagulant drugs. According to statistics, the total incidence rate of CSDH is 13.5/100,000 people per year, but among people over 65 years old, the incidence rate of CSDH has increased three times, approaching 58.1/100,000 people per year. With the aging population, the challenges faced by treating and managing CSDH patients are also increasing, and we may need a more suitable treatment method to reduce the risk of CSDH recurrence.

Although Atorvastatin monotherapy and middle meningeal artery embolization are reported to be effective [ 9 ], surgical removal of hematoma is still a consensus in the treatment of chronic subdural hematoma patients with neurological symptoms [ 10 , 11 ]. Chronic subdural hematomas are commonly treated with burr hole drainage (BHC) with closed drainage systems [ 12 ], while other surgical methods include endoscopic treatment, Fried Dough Twists drill drainage, and craniotomy. Endoscopic techniques, including rigid neuroendoscopy and soft neuroendoscopy, have been used for the treatment of chronic subdural hematoma for over 20 years [ 13 ]. In recent years, there have been studies suggesting that neuroendoscopy is more effective than drilling and drainage. Comparative studies between rigid neuroendoscopy and drilling and drainage have shown that rigid neuroendoscopy is superior to drilling and drainage in reducing recurrence and complication rates, thereby improving patient prognosis [ 14 ]. Thus, we conducted a meta-analysis to examine the effect of neuroendoscopy-assisted surgery in patients with chronic subdural hematoma.

A chronic subdural hematoma is treated primarily based on its clinical manifestations and cranial imaging findings, which can be divided into surgical treatment and nonsurgical treatment. If the hematoma occupying effect is obvious and causes clinical symptoms, surgical treatment is usually the first choice. Only a small number of patients with chronic subdural hematoma can absorb the intracranial hematoma on their own after non-surgical treatment, surgical treatment mainly includes large or small bone flap craniotomy, drilling and drainage, neuroendoscopic hematoma removal, minimally invasive puncture and drainage, and middle meningeal artery embolization. Surgical treatment is still the most effective treatment method for CSDH patients, because drilling and drainage is a simple and easy-to-apply technique, and drilling and drainage treatment significantly alleviates clinical symptoms. Therefore, drilling and drainage surgery is the most commonly used method for clinical treatment of CSDH [ 34 , 35 , 36 ].

Drilling is the main treatment for chronic subdural hematoma. Its complications include intracranial infection, brain tissue injury, intracranial hemorrhage, poor drainage of hematoma, postoperative recurrence, postoperative cerebrospinal fluid leakage, tension pneumocephalus, epilepsy, and postoperative Disorders of consciousness. The recurrence rate of chronic subdural hematoma treated with drilling surgery is 11.7 ~ 12.1%. At present, research has found that closed drainage can significantly reduce the recurrence rate of chronic subdural hematoma, thereby clarifying the necessity of drainage. Level I evidence strongly supports the closure system drainage of the subdural space after drilling, as the recurrence rate and hospitalization time are significantly reduced. Therefore, if feasible, temporary drainage pipes under the dura mater or cap-like aponeurosis should be retained to drain any fluid that accumulates immediately after surgery. Due to the risk of cortical injury, epilepsy, and infection associated with subdural drainage, the cap-like aponeurosis drainage tube is considered a minimally invasive alternative method. Preliminary studies have shown that the recurrence rate and complication rate of the two methods are statistically equivalent. In addition, prospective randomized trials are needed to fully determine whether the efficacy and outcomes of the cap-like aponeurosis drainage tube and the subdural drainage are comparable [ 37 , 38 ].

For partitioned CSDH, simple skull drilling drainage often leads to residual and recurrent hematoma due to poor drainage, with a recurrence rate of up to 21% reported in the literature. Porous drilling and drainage or repeated operations or even Craniotomy are often required, with large trauma, relatively increased surgical complications, long recovery time, and high treatment costs. Thoroughly removing liquefied and non-liquefied materials under direct vision of neuro endoscopy, and conventional drilling and drainage surgery can only blindly place drainage tubes into the subdural cavity due to the inability to effectively expose and observe hematoma. Sometimes, intraoperative damage may occur due to narrow or hard drainage spaces, such as vascular damage or insertion into brain tissue. It is also difficult to completely remove the hematoma during surgery, so it is necessary to retain the drainage tube, which can lead to a second extubation after surgery and a risk of intracranial infection. Hematoma or flocculent matter and thoroughly clean the hematoma cavity. For partitioned subdural hematomas, direct vision can safely separate and completely remove the contents of each hematoma cavity, achieving the goal of effectively clearing partitioned subdural hematomas. However, due to the inability of rigid endoscopes to bend, attention should be paid to the compliance of instrument operation to reduce surgical complications such as brain contusion and laceration, hematoma, and cerebral infarction. Long-term endoscopic training and experience accumulation are needed to compensate for the shortcomings. In recent years, with the development of neuroendoscopy technology, soft neuroendoscopy has gradually emerged in the treatment of CSDH. Soft neuroendoscopy, due to its advantages such as being able to change direction and angle arbitrarily, having a thin outer diameter, and being flexible in operation, is more suitable for imaging separated subdural hematomas.

A total of 20 literatures were included in this study, including 898 patients in the experimental group and 1448 patients in the control group. Meta-analysis showed that patients with chronic subdural hematoma who received neuroendoscopy-assisted surgery had a lower level of recurrence rate than controls. Meta-analysis showed a satisfactory Recurrence rate for the experimental group (OR 0.27; 95% Cl 0.18, 0.38; P < 0.01) and patients treated with neuroendoscopy-assisted surgery had relatively less recurrence in patients with septatus chronic subdural hematoma (OR 0.28; 95% Cl 0.12, 0.64; P < 0.01). Based on the results of the meta-analysis of recovery rate, compared to the control group, meta-analysis showed that the recovery rate of the test group was significantly higher (OR 1.18; 95% Cl 1.01, 1.38; P = 0.03). Based on the results of the meta-analysis of the total effective rate, compared to the control group, a meta-analysis showed that the total effective rate of the test group was significantly higher (OR 1.11; 95% Cl 1.04, 1.17; P < 0.01). Based on the results of the meta-analysis of operative time, compared to the control group, a meta-analysis showed that the operative time of the test group was significantly higher (SMD 15.78; 95% Cl 9.69, 21.86; P < 0.01). Meta-analysis showed that the hospital stay of the experimental group was significantly lower (SMD - 1.66; 95% Cl - 2.17, - 1.14; P < 0.01). For the results of the meta-analysis of complications, compared with the control group, a meta-analysis showed that the complications of the test group were significantly lower (OR 0.48; 95% Cl 0.30, 0.78; P < 0.01).

There are several limitations to this systematic review: it only searched Chinese and English literature, and no other languages were searched, and bias in the selection of studies may have been present. Therefore, you should be objective about some of the results of this meta-analysis.

In this study, neuroendoscopy-assisted surgery was effective in treating chronic subdural hematoma, as evidenced by a low recurrence rate, a high recovery rate, a high total effective rate, a short operation time, a short hospital stay and few complications, and the above conclusions need to be verified by more high-quality studies.