Chronic subdural hematoma (csdh) is one of the. Acute intracranial bleeding and recurrence after bur hole craniostomy for chronic subdural hematoma

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1 clinical article J Neurosurg 123:65 74, 2015 Acute intracranial bleeding and recurrence after bur hole craniostomy for chronic subdural hematoma *Chang Hwan Pang, MD, 1 Soo Eon Lee, MD, 1 Chang Hyeun Kim, MD, 1 Jeong Eun Kim, MD, PhD, 1,3 Hyun-Seung Kang, MD, PhD, 1,3 Chul-Kee Park, MD, PhD, 1,3 Sun Ha Paek, MD, PhD, 1,3 Chi Heon Kim, MD, 1,3 PhD, Tae-Ahn Jahng, MD, PhD, 2,3 Jin Wook Kim, MD, 2 Yong Hwy Kim, MD, 1 Dong Gyu Kim, MD, PhD, 1,3 Chun Kee Chung, MD, PhD, 1,3 Hee-Won Jung, MD, PhD, 1,3 and Heon Yoo, MD, PhD 4 1 Department of Neurosurgery, Seoul National University Hospital; 2 Department of Neurosurgery, Bundang Seoul National University Hospital; 3 Department of Neurosurgery, Seoul National University College of Medicine; and 4 Department of Neurosurgery, National Cancer Center, Seoul, Korea Object There is inconsistency among the perioperative management strategies currently used for chronic subdural hematoma (csdh). Moreover, postoperative complications such as acute intracranial bleeding and csdh recurrence affect clinical outcome of csdh surgery. This study evaluated the risk factors associated with acute intracranial bleeding and csdh recurrence and identified an effective perioperative strategy for csdh patients. Methods A retrospective study of patients who underwent bur hole craniostomy for csdh between 2008 and 2012 was performed. Results A consecutive series of 303 csdh patients (234 males and 69 females; mean age years) was analyzed. Postoperative acute intracranial bleeding developed in 14 patients (4.57%) within a mean of 3.07 days and recurrence was observed in 37 patients (12.21%) within a mean of days (range days) after initial bur hole craniostomy. The comorbidities of hematological disease and prior shunt surgery were clinical factors associated with acute bleeding. There was a significant risk of recurrence in patients with diabetes mellitus, but recurrence did not affect the final neurological outcome (p = 0.776). Surgical details, including the number of operative bur holes, saline irrigation of the hematoma cavity, use of a drain, and type of postoperative ambulation, were not significantly associated with outcome. However, a large amount of drainage was associated with postoperative acute bleeding. Conclusions Bur hole craniostomy is an effective surgical procedure for initial and recurrent csdh. Patients with hematological disease or a history of prior shunt surgery are at risk for postoperative acute bleeding; therefore, these patients should be carefully monitored to avoid overdrainage. Surgeons should consider informing patients with diabetes mellitus that this comorbidity is associated with an increased likelihood of recurrence. Key Words acute intracranial bleeding; bur hole craniostomy; chronic subdural hematoma; recurrence; traumatic brain injury Chronic subdural hematoma (csdh) is one of the most common pathologies associated with intracranial hemorrhage and may result in brain compression and subsequent neurological dysfunction. 2 The incidence of csdh increases proportionally with age; recent estimates of the csdh incidence in Japan were 20.6 cases per 100,000 population per year for patients years old and cases per 100,000 population per year for patients older than 80 years. 11 In an aging population, csdh patients comorbidities can affect clinical outcome due to the development of postoperative complications. For example, use of antiplatelet and anticoagulant medications is a risk factor for hemorrhage in an elderly population. 17,20 Abbreviations csdh = chronic SDH; SDH = subdural hematoma; VP = ventriculoperitoneal. submitted May 29, accepted December 18, include when citing Published online February 13, 2015; DOI: / JNS Disclosure The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper. This work was supported by the Korean Brain and Spinal Cord Research Foundation. * Drs. Pang and Lee contributed equally to this work. AANS,

2 C. H. Pang et al. Previous reports have indicated complication rates of 0% 34% and csdh recurrence rates of 0.35% 60% after csdh surgery, thus the need for effective surgical management strategies that can minimize complication and recurrence rates. 18,23,24,26 However, there are different opinions among neurosurgeons over the relative effectiveness of the various surgical management strategies currently used for csdh; these strategies include surgical techniques such as twist-drill craniostomy and bur hole craniostomy or craniotomy. 6,8,9,12,14,15,22 In our institution, bur hole craniostomy under local anesthesia has been the treatment of choice for patients with symptomatic csdh. Moreover, we consider bur hole craniostomy to be the simplest procedure for recurrent csdh. Even though csdh is one of the most frequently encountered intracranial pathologies in our institution, the details of the perioperative techniques, such as the number of operative bur holes, the use of saline irrigation to the hematoma cavity, the use of drains, and the staging of postoperative ambulatory activity, vary according to the individual surgeon. 2,6,12,19 In our experience, acute intracranial bleeding after bur hole craniostomy may occur after surgery and is related to a poor clinical outcome. Thus, it is important to identify the clinical and perioperative risk factors associated with postoperative acute bleeding and csdh recurrence. Hence, we conducted a retrospective cohort study to evaluate clinical factors associated with postoperative acute intracranial bleeding and csdh recurrence and to identify an optimal perioperative strategy for bur hole craniostomy in csdh patients. Methods Patients who underwent bur hole craniostomy for csdh between January 2008 and December 2012 were included in this study. Institutional review board approval was received, and all patients were from a single institution (Seoul National University Hospital). All cases of csdh were confirmed on the basis of CT scanning results. The location of the csdh was identified as unilateral or bilateral. Patient sex, age at surgery, and present age were obtained from the medical charts. The investigated comorbidities, diagnosed by the primary physician, were diabetes mellitus, hypertension, heart disease, liver disease, renal disease, cerebrovascular disease, hematological disease, and malignancy. Diabetes mellitus was defined as fasting plasma glucose level 126 mg/dl or 2-hour plasma glucose level 200 mg/dl during an oral glucose tolerance test. Hypertension was said to be present if the patient s blood pressure was higher than 140/90 mm Hg. Hematological disease included hemoglobinopathy, anemia, myelodysplastic syndrome, thrombocytopenia, myeloproliferative disorder, and coagulopathy. Hematological malignancy was also classified as a hematological disease, and malignancy was defined as a solid tumor. TABLE 1. Patient characteristics* Variable Total (n = 303) Recurrence Present (n = 14) Absent (n = 289) p Value Present (n = 37) Absent (n = 266) p Value M/F 234:69 12:2 222: :11 208: Mean age at surgery (yrs) ± ± ± ± ± Mean present age (yrs) ± ± ± ± ± Mean hospital stay (days) ± ± ± < ± ± Mean follow-up (mos) ± ± ± ± ± * The value in boldface is statistically significant. TABLE 2. Patient comorbidities* Comorbidity Total (n = 303) Recurrence Present (n = 14) Absent (n = 289) p Value Present (n = 37) Absent (n = 266) p Value DM 78 (25.7%) HTN 145 (47.9%) Heart disease 57 (18.8%) Liver disease 25 (8.3%) Renal disease 40 (13.2%) Hematological disease 25 (8.3%) 6 19 < Malignancy 13 (4.3%) Cerebrovascular disease 46 (15.3%) Previous shunt surgery 8 (2.6%) Previous craniotomy 18 (5.9%) DM = diabetes mellitus; HTN = hypertension. * Values in boldface are statistically significant. 66

3 Bur hole craniostomy for chronic subdural hematoma The following factors were assessed: history of ventriculoperitoneal (VP) shunt surgery and craniotomy, recent use of antiplatelet or anticoagulant medication and the time to restart these medications after surgery, and the use of transfusion of platelet or fresh frozen plasma before bur hole craniostomy. Bur hole craniostomy was performed under local anesthesia. Surgical procedures included items that corresponded to the surgeon s preference. Perioperative surgical management details derived from the operative records were investigated. The total amount of hematoma drainage, number of days before drain removal, duration of hospital stay, and follow-up period were determined. Each patient s neurological status was based on the Markwalder neurological grading system, and his or her status was determined at the initial preoperative visit, at discharge, and at the postoperative 6-month and final follow-ups. 15 Markwalder grades are classified as Grade 0, patient neurologically normal; Grade 1, patient alert and oriented with mild symptoms such as headache or with absent or mild symptoms or neurological deficit such as reflex asymmetry; Grade 2, patient drowsy or disoriented with a variable level of neurological deficit such as hemiparesis; Grade 3; patient stuporous, but would respond appropriately to noxious stimuli, and severe focal signs such as hemiparesis are present; and Grade 4, patient comatose with absent motor response to painful stimuli and decerebrate or decorticate posturing. The investigated postoperative complications included surgery-related complications, acute intracranial bleeding, wound infection, seizure, and hydrocephalus. Acute intracranial bleeding was identified as a high-density lesion Table 3. Use of antiplatelet and anticoagulant medications* Variable Total (n = 303) Recurrence Present (n = 14) Absent (n = 289) p Value Present (n = 37) Recurrence (n = 266) p Value None 191 (63.0%) Medication use 112 (37.0%) Antiplatelet 81 (26.7%) Anticoagulant 23 (7.6%) Both 8 (2.6%) Mean no. of days until restart of these medications ± ± ± ± ± * The value in boldface is statistically significant. TABLE 4. Surgical details* Variable Total (n = 303) Recurrence Present (n = 14) Absent (n = 289) p Value Present (n = 37) Absent (n = 266) p Value Side of op Unilateral 247 (81.5%) Bilateral 56 (18.5%) No. of operative bur holes (70.3%) (29.7%) Saline irrigation Yes 255 (84.2%) No 48 (15.8%) Drain insertion Yes 207 (68.3%) No 96 (31.7%) Postop ambulation Yes 83 (27.7%) No 220 (72.6%) Mean total amount of ± ± ± ± ± drainage (ml) Mean no. of days until drain removal 2.59 ± ± ± ± ± * The value in boldface is statistically significant. 67

4 C. H. Pang et al. in the brain parenchyma or subdural space visible on CT scanning and with neurological deterioration. Recurrence of csdh was defined as a clinically and radiologically confirmed csdh occurring on the ipsilateral side within 6 months of the initial surgery and requiring a repeat bur hole craniostomy. Statistical Analysis Data are presented as the means ± SD. Statistical analysis was performed using the Student t-test for continuous variables and the chi-square or Fisher s exact tests for categorical variables. Logistic regression analysis was used for multivariate analyses. A linear mixed model was used to analyze clinical outcomes. A value of p < 0.05 was considered significant, and SPSS software (version 19.0, IBM) was used for the statistical analysis. Results Data from a consecutive series of 303 patients (234 males and 69 females) were analyzed (Table 1). The mean age at surgery was ± years (range years); 286 patients were 60 years or older, and 67 patients were younger than 60 years. At final follow-up, the mean age was ± years (range years). The average number of comorbidities was 1.50 ± 1.27 (range 0 6). Fig. 1. Neurological outcome based on Markwalder grades. Upper: The initial preoperative Markwalder grade was significantly different in patients with acute bleeding from that in those without bleeding. Most of the patients with acute bleeding presented with drowsiness and neurological deficits. Postoperative acute bleeding complications could result in a poor neurological outcome in these patients (*p = 0.049). Lower: During follow-up, there was no significant difference in neurological outcome in patients with or without csdh recurrence (p = 0.776). F/U = follow-up; POD = postoperative day. There were 78 patients (25.7%) with diabetes mellitus, 145 (47.9%) with hypertension, 57 (18.8%) with heart disease, 25 (8.3%) with liver disease, 40 (13.2%) with renal disease, 46 (15.3%) with cerebrovascular disease, 25 (8.3%) with hematological disease, and 13 (4.3%) with a malignancy (Table 2). Eight patients (2.6%) had a VP shunt and 18 patients (5.9%) had previously undergone craniotomy. One hundred twelve patients (37.0%) had taken antiplatelet or anticoagulant medications; among them, 8 patients (2.6%) used both antiplatelet and anticoagulant medications (Table 3). Platelet transfusion was not routinely performed in patients receiving an antiplatelet agent. Patients with thrombocytopenia from liver disease (16 patients), renal disease (23 patients), hematological disease (22 patients), and malignancy (6 patients) received platelet transfusion. Thirty-one patients on a regimen of warfarin therapy with confirmed coagulation abnormality received fresh frozen plasma with vitamin K for prothrombin time reversal. With regard to surgical details, a unilateral bur hole craniostomy approach was used in 247 patients (81.5%) and a bilateral approach was used in 56 (18.5%, Table 4). A single operative bur hole was made in 213 patients (70.3%) and 2 holes were made in 90 patients (29.7%). Saline irrigation of the hematoma cavity was performed in 255 patients (84.2%), and a drain was inserted in 207 (68.3%). The mean total hematoma drainage amount was ± ml (range ml), and the mean duration prior to drain removal was 2.59 ± 1.81 days (range 0 17 days). Postoperative ambulation was permitted in 83 patients (27.7%), whereas 220 patients (72.6%) were kept on bed rest. The mean length of hospital stay was ± days (range days), and the mean follow-up duration was ± months (range months). The mean Markwalder grades were 1.84 ± 0.58 at the initial preoperative visit and 0.48 ± 0.84 at discharge. The Markwalder grade averaged 0.41 ± 0.88 for the 284 patients with a 6-month postoperative follow-up visit and 0.33 ± 0.76 for the 210 patients with a final follow-up visit (Fig. 1). Postoperative complications developed in 23 patients (7.59%): 14 (4.57%) had acute intracranial bleeding, 6 (1.98%) had wound infection, 5 (1.65%) suffered seizure, and 2 (0.66%) had hydrocephalus. Recurrence occurred in 37 patients (12.21%); death occurred in 5 patients (1.65%; 4 patients with postoperative acute bleeding and 1 patient with recurrence at 1 month postoperatively who died 5 months later due to lung cancer progression). The average time to restart antiplatelet or anticoagulant treatment after initial bur hole craniostomy was ± days (range 3 60 days). Comparative Analysis of Patients With Postoperative Fourteen patients (12 males and 2 females; mean age at surgery ± years) developed postoperative acute intracranial bleeding (Table 5). Acute bleeding developed at an average of 3.07 ± 2.49 days (range 0 7 days) after bur hole craniostomy. Compared with patients without acute intracranial bleeding, the presence of renal disease, hematological disease, and prior VP shunt surgery were significant comorbidities in patients with acute 68

5 Bur hole craniostomy for chronic subdural hematoma TABLE 5. Patients with postoperative acute intracranial bleeding Case No. Age (yrs), Sex Comorbidity Type of Acute Bleeding Time Interval to (days) Complication Management Clinical Course According to Markwalder Grade* 1 47, F AF on warfarin, thrombocytopenia ICH 2 Craniectomy , M DM, HTN, antiplatelet SDH 7 Craniectomy , M DM, HTN; prior VPS SDH 2 Craniectomy , M Myelodysplastic disease SDH 1 Craniectomy , M HTN ICH 1 Stereotactic aspiration , M HTN, antiplatelet SDH 5 Bur hole craniostomy , M HTN, heart disease; prior VPS; antiplatelet, SDH 1 Bur hole craniostomy 2 1 anticoagulant 8 44, M Prior craniotomy d/t SAH; previous VPS SDH 3 Bur hole craniostomy , F Prior craniotomy d/t head trauma SDH 3 Bur hole craniostomy , M DM, HTN, MI; antiplatelet ICH 6 Observation , M DM, HTN; heart disease, HCC SDH 7 Op intolerable 2 death 12 66, M DM, HTN; heart disease; DIC; anticoagulant SDH 0 Op intolerable 3 death 13 58, M Prostate cancer; DIC SDH 0 Op intolerable 3 death 14 76, M Hypoplastic anemia SDH 5 Op intolerable 2 death AF = atrial fibrillation; DIC = diffuse idiopathic coagulopathy; d/t = due to; HCC = hepatocellular carcinoma; ICH = intracranial hemorrhage; MI = myocardial infarction; SAH = subarachnoid hemorrhage; SDH = subdural hematoma; VPS = VP shunt. * The preoperative Markwalder grade is listed first, followed by the final score the patient was known to achieve. Fig. 2. CT scans obtained in an 85-year-old man with hematological disease. This patient underwent treatment for myelodysplastic syndrome and fell from bed 3 days prior to presentation at the hospital s emergency department. He had developed drowsiness. The initial brain CT scan (A) demonstrated a slightly high-density hematoma in the left hemisphere. The patient underwent a bur hole craniostomy via 2 bur holes with intraoperative saline irrigation and drain insertion. Postoperative CT scan obtained immediately postoperatively (B) showed a small amount of residual hematoma. One day after the operation, the patient complained of headache, and a follow-up CT evaluation (C) demonstrated SDH with a high-density lesion. Hence, the patient underwent craniotomy and hematoma removal. Postoperatively, a residual hematoma (D) was observed and was associated with tolerable clinical symptoms. Over the postoperative period, at 3 months (E) and 11 months (F), the hematoma gradually decreased. 69

6 C. H. Pang et al. Fig. 3. CT scans obtained in a 44-year-old man with a prior history of VP shunt surgery. This patient underwent craniotomy and clipping for a ruptured aneurysm and VP shunt placement 6 months after craniotomy. At that point, the pressure of the VP shunt s programmable valve was adjusted. One year after VP shunt surgery, the patient developed dysarthria and a behavioral change. A brain CT scan obtained at that time (A) demonstrated a right-sided SDH. After setting the VP shunt to high pressure, a bur hole craniostomy was performed and the brain CT scan (B) obtained immediately postoperatively showed a decreased extent of the hematoma. However, the follow-up CT scan on postoperative Day 3 (C) showed increased hematoma content with an acute portion. The patient underwent ligation of the distal shunt catheter and he underwent a second bur hole craniostomy (D). A residual hematoma was observed 1 month postoperatively (E), but the patient s clinical symptoms were much improved. At 12 months postoperatively, there was a good radiological image (F). bleeding (p = 0.025, < 0.001, and 0.004, respectively; Table 2). The use of antiplatelet or anticoagulant medication was not related to the occurrence of postoperative acute bleeding (p = 0.396, Table 3). None of the surgical details was significantly different between patients with and without postoperative acute bleeding. Acute bleeding associated with drain removal was not observed in patients in whom a drain was placed. However, the average total amount of hematoma drainage was significantly greater in patients with postoperative acute bleeding ( ± ml) than that in patients without acute bleeding ( ± ml, p = 0.037). The average length of hospital stay was significantly longer for patients with postoperative acute bleeding (31.73 ± days) than that for patients without acute bleeding (11.24 ± days, p < 0.001). In addition, the restart time for antiplatelet or anticoagulant medication was delayed in patients with acute bleeding (29.50 ± days) compared with that in patients without acute bleeding (20.31 ± 9.67 days, p = 0.014). In patients with acute bleeding, the preoperative average Markwalder grade was poorer than that in patients without acute bleeding (p = 0.014), and the significance of the score difference was maintained during follow-up (p < at discharge, p = at 6 months postoperatively, and p = at final follow-up). Moreover, a linear mixed model analysis of Markwalder grades showed a significant difference between patients with and without postoperative acute bleeding during follow-up (p = 0.049, Fig. 1 upper). Logistic regression analysis of clinical factors associated with postoperative acute bleeding indicated that the significant factors were hematological disease (p < 0.001, OR [95% CI ]), previous VP shunt surgery (p < 0.001, OR [95% CI ]), and initial preoperative Markwalder grade (p = 0.011, OR [95% CI ]). Typical case illustrations are presented in Figs. 2 and 3. Comparative Analysis of Patients With Recurrence Thirty-seven patients (26 males and 11 females; mean age at surgery ± 8.32 years) underwent a second bur hole craniostomy because of csdh recurrence at an average of ± days (range days) after the initial bur hole surgery. Among the assessed comorbidities for recurrence, diabetes mellitus was the only clinical factor significantly associated with recurrence (p = 0.027, Fig. 4 upper). The use of antiplatelet or anticoagulant medications was not associated with recurrence (p = 0.368, Fig. 4 lower), and 70

7 Bur hole craniostomy for chronic subdural hematoma (p = 0.776, Fig. 1 lower). Details for a patient with recurrence are shown in Fig. 5. Analysis for Perioperative Management Strategies In our assessment of the effectiveness of various perioperative management strategies, several patients were excluded. The excluded patients were those younger than 60 years (67 patients) and those with hematological disease (20 patients), malignancy (9 patients), previous VP shunt surgery (7 patients), previous craniotomy (10 patients), bilateral csdh (30 patients), and 2 operative bur holes (49 patients). As a result, data for 111 patients 60 years or older who underwent single, unilateral bur hole craniostomy for csdh were analyzed. One (0.90%) of those patients developed postoperative acute bleeding, whereas 13 (11.71%) had recurrence. The use of saline irrigation of the hematoma cavity, drain insertion, and type of postoperative ambulation were not significantly different in patients with or without recurrence (all p > 0.05). Fig. 4. Kaplan-Meier curve for recurrence. Among the assessed comorbidities, diabetes mellitus (DM) (upper) was the only clinical factor associated with recurrence, and use of antiplatelet or anticoagulant therapy (lower) was not associated with recurrence. no other surgical detail was significantly associated with recurrence. Restart time of antiplatelet or anticoagulant agents was not different in patients with or without recurrence (p = 0.816). Logistic regression analysis of the clinical factors that may be associated with recurrence indicated that diabetes mellitus was the only significant risk factor for recurrence (p = 0.034, OR [95% CI ]). Markwalder grades were not different between patients with and without recurrence preoperatively (p = 0.600), at discharge (p = 0.827), or at the postoperative 6-month follow-up (p = 0.626) and final follow-up (p = 0.815) visits. In addition, linear mixed model analysis indicated no significant difference in neurological outcome during follow-up in patients with and without recurrence Discussion Interpretation of Surgical Details We undertook a single-center cohort study of a consecutive series of 303 patients who underwent bur hole craniostomy under local anesthesia for csdh. The clinical data records for these patients were analyzed to elucidate factors that might be associated with bur hole craniostomy outcome. The present study s complication rate (7.59%) and csdh recurrence rate (12.21%) are comparable to those reported previously. 18,23,24,26 Various surgical techniques have been used in an attempt to decrease recurrence, but there are differences of opinion among neurosurgeons regarding the relative effectiveness of those techniques. Previous retrospective analyses of more than 200 patients with csdh treated by single or double bur hole surgery indicated no difference in efficacy in the treatment of csdh. 10,21 Some researchers have suggested that there is no improvement in the csdh mortality, morbidity, and recurrence rates associated with saline irrigation of the hematoma cavity. 2,7 In contrast, a meta-analysis of 5 randomized trials indicated a significant reduction in recurrence rate when drains were inserted following hematoma evacuation. 2,25 Three randomized trials comparing bed rest and ambulation after surgery showed these 2 postoperative approaches to be equally beneficial with no significant complication associated with either type of mobilization. 1,2 At our institution, surgeons preferences when performing bur hole craniostomy were diverse. A single operative bur hole, saline irrigation of the hematoma cavity, drain insertion, and postoperative bed rest were undertaken in 70% 80% of the surgical management strategies used at our institution. None of these perioperative differences resulted in significant differences in postoperative complication and recurrence rates. Therefore, we advocate the use of bur hole craniostomy with a single operative bur hole, drain insertion without saline irrigation, and postoperative ambulation. In our experience, these perioperative management strategies consume little time during surgery, and, with the addition of ambulation, elderly patients may avoid complications related to prolonged bed rest. Re- 71

8 C. H. Pang et al. Fig. 5. CT scans obtained in a 76-year-old man who experienced csdh with recurrence. This patient presented with headache and dysarthria. His comorbidity was diabetes mellitus, and he had taken an antiplatelet agent. On the initial brain CT scan (A), an SDH in the left hemisphere was observed, which was treated with a bur hole craniostomy (1 bur hole) with intraoperative saline irrigation. No drain was inserted, and the CT scan obtained immediately postoperatively revealed no hematoma, but a pneumocephalus was present (B). The patient was discharged 3 days later (C). His alertness decreased, and at 35 days after the operation recurrence was identified on the CT scan (D). A second bur hole craniostomy for hematoma removal was performed (E). Brain parenchyma had expanded by 1 month postoperatively (F). gardless, prospective randomized studies into the use of saline irrigation and postoperative ambulation should be conducted to determine the most effective perioperative strategies for csdh treatment. Clinical Factors Associated With Outcomes In contrast to suggestions that the use of antiplatelet or anticoagulant medications might increase the csdh recurrence rate, patients in our study who had taken antiplatelet or anticoagulant medication were not more likely to develop acute bleeding or have recurrence rates higher than those who did not take such medication. Other studies have also reported no relationship between the use of these medications and csdh recurrence. 3,13 Although further studies may be needed to determine how to manage csdh preoperatively, the use of fresh frozen plasma and vitamin K plasma in patients taking anticoagulants and the transfusion of platelets in patients taking antiplatelet medication may help in some csdh cases. Regardless, if patients using antiplatelet or anticoagulant medications present with symptoms related to csdh, surgical management of the csdh can be performed immediately with subsequent resumption of these medications as necessary. Patients in our study with postoperative acute intracranial bleeding had a poor clinical course after bur hole craniostomy. Most of these patients presented with drowsiness and neurological deficits. Hematological disease as an underlying comorbidity induces thrombocytopenia and coagulopathy and, in our study, was a risk factor for the development of acute intracranial bleeding. A poor general condition that cannot tolerate surgery can result in a fatal clinical course. In addition, patients with prior VP shunt surgery are at risk for developing acute intracranial bleeding after bur hole craniostomy. The occurrence of SDH after VP shunt surgery is rare and may be associated with overdrainage of CSF. 4,16 The management of SDH occurring after shunt surgery includes shunt ligation, shunt valve pressure control, bur hole craniostomy, and combination therapy. 5 In the present study, patients with a shunt underwent combination therapy, which consisted of shunt ligation or provision of high shunt valve pressure combined with bur hole craniostomy. Three of the 8 patients who had undergone prior VP shunt surgery in our study developed acute SDH and underwent bur hole craniostomy or craniectomy for hematoma removal. An optimal management strategy for csdh following VP shunt surgery should be established. With regard to overdrainage of CSF, we note that a large amount of hematoma (about > 400 ml) was drained in those patients with acute bleeding. Although the drainage color was not recorded for our series of patients, the drainage might not be only hematoma, but it might be a mixture of hematoma and CSF. Our results indicate that drainage of more than 400 ml of CSF might increase the risk of intracranial bleeding. Thus, drainage amounts should be limited. Recurrence of csdh occurred in 12.21% of patients in this study and developed approximately 1 month after bur hole craniostomy. Long-term neurological outcome in patients with csdh recurrence did not differ from that in patients without recurrence. Repeat bur hole craniostomy has been suggested as the simplest surgical strategy for recurred csdh. Patients with diabetes mellitus had a higher 72

9 Bur hole craniostomy for chronic subdural hematoma rate of recurrence, indicating that diabetes mellitus is a risk factor for recurrence. Limitations of the Study The present study had a retrospective design, which typically produces inherent biases associated with retrospective studies. Hence, we expected less accurate results than those from a prospective, randomized study. In this study, data from a 5-year-long ( ) patient series were analyzed, but the mean follow-up period was relatively short (14 months). Because a good neurological recovery was observed in patients without complications and recurrence after bur hole craniostomy, it does not appear that the short follow-up period in our study significantly affected the results. In our clinical experience, the mixed density of a hematoma with multiseptate hematoma membranes might affect the hematoma remnant left after bur hole craniostomy. These factors may also affect recurrence, and additional craniostomy may be needed for a mixed-stage hematoma. Analysis of radiological data was not included in the present study, but the relationship of such data with csdh treatment outcome should be investigated further. The sole risk factor for recurrence in the present study was diabetes mellitus, but we did not determine the exact disease status of the diabetes mellitus. Although patients with diabetes mellitus Types I and II were included, details of disease management (for example, use of diabetes mellitus medication or insulin injection and lifestyle modification) were not investigated. Thus, further evaluation of how to manage diabetes mellitus and csdh is needed. Regardless, the comparatively large sample size (303 patients from a single institution) gives our study sufficient strength to identify the clinical factors that were associated with postoperative acute intracranial bleeding and csdh recurrence. While surgeon s preferences provided diverse perioperative surgical approaches, none of those surgical details appeared to affect outcome significantly. Regardless, prospective studies into the efficacies of saline irrigation and postoperative ambulation should be undertaken to determine their relation to a successful clinical outcome. Conclusions Bur hole craniostomy is an effective surgical procedure for initial and recurrent csdh. Patients with hematological disease or prior VP shunt surgery are at risk for acute intracranial bleeding; therefore, such patients should be carefully monitored to avoid overdrainage of CSF. A medical history of diabetes mellitus was associated with csdh recurrence; thus, surgeons should inform patients with diabetes mellitus of that risk. Various perioperative strategies, such as the number of operative bur holes, the use of saline irrigation, drain insertion, and type of postoperative ambulation, were not significantly associated with the prevention of postoperative acute bleeding and csdh recurrence. Prospective studies of the relationships of those strategies with csdh outcome should be undertaken. References 1. Adeolu AA, Rabiu TB, Adeleye AO: Post-operative day two versus day seven mobilization after burr-hole drainage of subacute and chronic subdural haematoma in Nigerians. Br J Neurosurg 26: , Almenawer SA, Farrokhyar F, Hong C, Alhazzani W, Manoranjan B, Yarascavitch B, et al: Chronic subdural hematoma management: a systematic review and meta-analysis of 34,829 patients. Ann Surg 259: , Aspegren OP, Åstrand R, Lundgren MI, Romner B: Anticoagulation therapy a risk factor for the development of chronic subdural hematoma. 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10 C. H. Pang et al. trauma patients with mild traumatic brain injury. J Trauma Acute Care Surg 73: , Pahatouridis D, Alexiou GA, Fotakopoulos G, Mihos E, Zigouris A, Drosos D, et al: Chronic subdural haematomas: a comparative study of an enlarged single burr hole versus double burr hole drainage. Neurosurg Rev 36: , Reinges MH, Hasselberg I, Rohde V, Küker W, Gilsbach JM: Prospective analysis of bedside percutaneous subdural tapping for the treatment of chronic subdural haematoma in adults. J Neurol Neurosurg Psychiatry 69:40 47, Rohde V, Graf G, Hassler W: Complications of burr-hole craniostomy and closed-system drainage for chronic subdural hematomas: a retrospective analysis of 376 patients. Neurosurg Rev 25:89 94, Sambasivan M: An overview of chronic subdural hematoma: experience with 2300 cases. Surg Neurol 47: , Santarius T, Kirkpatrick PJ, Ganesan D, Chia HL, Jalloh I, Smielewski P, et al: Use of drains versus no drains after burr-hole evacuation of chronic subdural haematoma: a randomised controlled trial. Lancet 374: , Van Der Veken J, Duerinck J, Buyl R, Van Rompaey K, Herregodts P, D Haens J: Mini-craniotomy as the primary surgical intervention for the treatment of chronic subdural hematoma a retrospective analysis. Acta Neurochir (Wien) 156: , 2014 Author Contributions Conception and design: Yoo, Lee. Acquisition of data: Pang, Lee, Chang Hyeun Kim. Analysis and interpretation of data: Pang, Lee, Chang Hyeun Kim. Drafting the article: Lee. Critically revising the article: Yoo, JE Kim, Kang, Park, Paek, Chi Heon Kim, Jahng, JW Kim, YH Kim, DG Kim, Chung, Jung. Reviewed submitted version of manuscript: Yoo, JE Kim, Kang, Park, Paek, Chi Heon Kim, Jahng, JW Kim, YH Kim, DG Kim, Chung, Jung. Approved the final version of the manuscript on behalf of all authors: Yoo. Statistical analysis: Lee. Study supervision: Kang. Correspondence Heon Yoo, Department of Neurosurgery, Specific Organs Cancer Center, National Cancer Center, 323 Ilsan-ro, Ilsandong-gu, Goyang-si, Gyeonggi-do , Korea. heonyoo@ncc.re.kr. 74