Our meta-analysis shows that the LA technique is superior to the GA technique in terms of complication, operation length, and hospital stay. Also, we did not find significant differences between GA and LA patients regarding recurrence rate, mortality, or reoperation.

This meta-analysis results align with those reported by Liu et al. [16] regarding mortality, postoperative recurrence, total duration of surgery, and postoperative complications. Regarding the length of hospital stay, in Liu's study, despite the analyzed studies separately favoring LA, their meta-analysis did not show significant differences. However, our analysis included studies that directly reported the length of stay without conversion and gained significant results in favor of LA. In theory, decreasing the overall duration of surgery should correspondingly reduce the likelihood of surgery-related complications, ultimately leading to shorter hospital stays. Additionally, reducing surgical time will likely decrease demand for post-anesthesia care units. Hence, we noticed that GA length of operation was higher than LA by 19 h (95% CI [15.77, 22.68], P < 0.00001). Therefore, LA was associated with a significantly lesser duration of hospital stay than GA, which agrees with previous studies [12, 16, 33, 37]. This is a potential advantage of utilizing LA in the surgical management of CSDH.

It is also worth mentioning that shortening the duration of surgery not only decreases the risk of thromboembolism, hypothermia, and intraoperative adverse events but also eliminates the specific risks associated with GA. Our findings suggested that the GA technique is associated with 2.4 times higher complications compared to the LA technique (95% CI [1.81, 3.17], P < 0.00001), similar to previous studies [12, 15, 25, 27, 33, 36,37,38].

Notably, the causes of death in CSDH may be associated with postoperative complications such as pulmonary infection, thrombosis, and underlying diseases. A retrospective analysis by Wong et al. [22] found that LA significantly reduced the mortality of patients compared with GA. However, regardless of the type of anesthesia, patient death may be associated with underlying diseases such as chronic kidney disease [25, 33]. Our analysis indicated that mortality was not significantly different between LA and GA (P = 0.96).

The association between LA and GA and the recurrence rate has been reported previously with conflicting results. Previous studies [24, 27, 32, 35] reported that the LA technique was associated with a significant recurrence rate compared to the GA technique, while other studies showed that the GA technique was associated with a significant recurrence rate compared to the LA technique [28, 30, 33, 34, 36,37,38]. However, in our meta-analysis, we included 16 studies and noticed an insignificant difference in recurrence between GA and LA (OR 0.95, 95% CI [0.78, 1.15], P = 0.59).

Research indicates that the recurrence rate of CSDH post-surgery ranges from 2.5% to 33%, with an increased likelihood in older individuals [39, 40]. The exact causes of relapses remain incompletely understood. Several factors contribute to this risk, including reduced brain tissue elasticity in elderly patients with brain atrophy due to CSDH compression, the persistence of a sizable subdural space post-surgery, the use of antiplatelet medications, stimulation of angiogenesis by growth factors, and inflammatory cytokines. Elevated levels of IL-6 in subdural fluid and factors enhancing the expression of outer membrane VEGF and bFGF also play roles in CSDH recurrence [41]. Effectively managing recurrent CSDH poses a significant challenge, and as highlighted in our previous review, proper drainage after burr-hole evacuation is crucial in mitigating this risk [10]. It is also important to mention that in some studies, recurrence can be defined as exposing the patient to reoperation on the same side [24], while other studies can report the reoperation rate separately. Alnaami et al. study suggested that GA is less associated with reoperation than LA [24], while other studies reported otherwise [27, 28, 36], and the overall analysis of these four studies remained insignificant (P = 0.87).

Although surgery for CSDH under results in fewer complications, a shorter hospital stay, and a briefer operation duration, it may not be suitable for all patients. Especially for patients with comorbidities, as described by Certo et al. [27], some individuals with pre-existing neurodegenerative disorders have experienced worsening of their symptoms. Additionally, a patient with Parkinson’s disease exhibited a deterioration in gait disturbances [27]. Generally, in pediatric cases, for instance, LA with sedation can lead to complications such as respiratory depression or atelectasis [42]. Conversely, GA can result in postoperative atelectasis, hemodynamic instability, and aspiration [43]. Therefore, we must choose the type of anesthesia very carefully based on the patient’s specific conditions.

Finally, it is essential to highlight the strengths and limitations of our analysis. To our knowledge, this is the first meta-analysis comprising 18 studies that compare intra-operative and postoperative complications between LA and GA. Among these studies, two were clinical trials, two were case–control studies, and the rest were cohort studies. Additionally, we conducted a rigorous quality assessment, rendering this meta-analysis valuable for clinical physicians in making informed decisions. Furthermore, including studies from various countries worldwide enhances the representativeness of this meta-analysis for the general population.

The limitations of this study include the predominantly observational nature of the research, comprising retrospective and prospective cohort studies, since the operations cannot be conducted blindly. Out of these studies, only two were clinical trials. Additionally, we faced challenges in extracting data from some studies, particularly the mean outcomes, such as the length of hospital stay and the Glasgow Coma Scale, due to unclear information in the papers. Even though we included the bias test for complications, reoperation, length of hospital stay, and length of operation, the number of studies included was less than 10. Hence, the power of this test is low in our analysis, making it difficult to distinguish between chance and real asymmetry. Therefore, the results of Egger’s test should be interpreted with caution.