POSTOPERATIVE CHRONIC SUBDURAL HEMATOMA FOLLOWING CLIP- PING SURGERY

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1 Nagoya postoperative Med. J., chronic subdural hematoma after aneurysmal clipping 13 POSTOPERATIVE CHRONIC SUBDURAL HEMATOMA FOLLOWING CLIP- PING SURGERY TAKAYUKI OHNO, M.D., YUSUKE NISHIKAWA, M.D., KIMINORI AOYAMA, M.D., KAZUO YAMADA, M.D., Ph.D., AND KOJI IIHARA, M.D., Ph.D. Department of Neurosurgery, National Cardiovascular Center, Suita, Japan Department of Neurosurgery, Nagoya City University, Nagoya, Japan Department of Neurosurgery, Nagoya City University, Nagoya, Japan Accepted for publication December, SUMMARY Object: Chronic subdural hematoma CSDH after aneurysm clipping is a rare complication, but the risk factors are not known in detail. We retrospectively reviewed cases requiring surgery for CSDH. Methods: Between January and December, consecutive patients in the National Cardiovascular Center underwent clipping or coating surgery for unruptured aneurysm of anterior circulation. We reviewed the incidence and risk factors of the development of CSDH after aneurysmal clipping, and focused on subdural fluid collection SFC and increase, reviewing CT scans after clipping over the last two years. Results: developed postoperative CSDH which required surgery. Risk factors of postoperative CSDH included advanced age p, and male gender p. Wecouldfindno significant difference between aneurysmal sites and postoperative CSDH. An increase of SFC over week postoperatively was also shown to be a significant risk factor for CSDH p. Conclusion: This study showed advanced age and male gender were significant factors in the formation of postoperative CSDH. We suggest that an increase of SFC over week postoperatively can be a factor predicting CSDH after clipping. Key word : clipping, postoperative chronic subdural hematoma, subdural fluid collection Corresponding Author s name and complete mailing address: Takayuki Ohno, M.D. Department of Neurosurgery Nagoya City University, Kawasumi, Mizuho-cho, Mizuho-ku Nagoya -,Japan Phone: ,Fax: , tohno@med.nagoya-cu.ac.jp 13

2 14 T. Ohno, et al. INTRODUCTION Chronic subdural hematoma CSDH is one of the most common neurosurgical disorders in the elderly and tends to occur several weeks after mild head injury. CSDH after clipping surgery is a rare complication. There are a few reports reviewing such complications -, but the risk factors are not known in detail. We reviewed cases requiring surgery for CSDH among cases of aneurysmal clipping in the National Cardiovascular Center for the past seven years. We also reviewed head CT findings after clipping surgery over the last two years. PATIENTS AND METHODS Patients Between January, and December,, consecutive patients underwent clipping or coating surgery for unruptured aneurysms of anterior circulation in the Department of Neurosurgery, National Cardiovascular Center. Baseline characteristics of these patients are listed in Table. Mean age ± standard deviation SD was ± years, and patients were male. aneurysms originated from the middle cerebral artery MCA and aneurysms originated from the anterior communicating artery A-com. A. aneurysms originated from the internal carotid artery ICA at the posterior communicating artery P-com.A, anterior choroidal artery, or ICA bifurcation. Table Data Collection We reviewed surgical records and clinical files in all cases. After clipping surgery, the patients were followed up with periodic CT scanning. In this study, the proposed clinical criteria for CSDH related to clipping were: postoperative CSDH occurring within months after clipping, and no history TABLE. Baseline characteristics of unruptured aneurysm cases included in present study a

3 postoperative chronic subdural hematoma after aneurysmal clipping 15 of head injury after clipping. We performed burr hole and irrigation surgery when the CT scan showed definite CSDH and progressive midline shift, or when the patient showed symptoms such as headache or hemiparesis. Results were analyzed for statistical significance using Fisher s exact test. For the last two years, we also collected all CT scan data for unruptured cases. In this period, only one case had a history of head injury after clipping. We excluded this case. We focused on subdural fluid collection SFC and increase after clipping. RESULT Incidence of CSDH We identified patients who developed postoperative CSDH requiring surgery among all the clipping cases. Table shows a summary of our results. With statistical analysis, we identified the risk factor as advanced age p and male gender p. We could find no significant differences between aneurysmal sites. The period from aneurysmal surgery to burr hole surgery for CSDH was - days median days, IQR: -. Recurring cases of CSDH were detected in patients, but three of those cases developed CSDH in the contralateral side of the craniotomy. All CSDH cases could be successfully treated with one or two burr holes and irrigation. Postoperative CT findings cases showed no postoperative SFC Fig. -A, B or a small quantity less than mm in maximal thickness which disappeared in a short period Fig. -C, D. cases gradually increased SFC after clipping surgery. of these cases developed CSDH, but they were gradually absorbed and disappeared spontaneously. cases required burr hole surgery for CSDH. SFC increased gradually and became CSDH, and the patients presented symptoms Fig.. An increase of SFC over week postoperatively was also shown to be a significant risk factor for CSDH p. Table TABLE. Factors affecting occurrence of CSDH after surgery for aneurysm on univariate analysis

4 16 T. Ohno, et al. FIG.. Postoperative CT scans showing the process in which the majority of SFC subside spontaneously. A. CT scan the day following clipping for unruptured right middle cerebral artery aneurysm. B. CT scan the day after clipping surgery showing no SFC. C. CT scan for another case the day after clipping for unruptured right middle cerebral artery aneurysm. D. CT scan the day after clipping surgery showing slight mm SFC. E. CT scan the week after clipping surgery showing no SFCs. FIG.. Postoperative CT scans showing the process leading to postoperative CSDH. A. CT scan the day following clipping for unruptured right middle cerebral artery aneurysm. B. CT scan the th day after clipping surgery showing slight mm SFC. C. CT scan the th day after clipping showing enlargement of SFC. D. CT scan the th day after clipping showing SFC replaced by iso density fluid collection, with mass effect. TABLE. Relationship between CSDH and postoperative CT findings

5 postoperative chronic subdural hematoma after aneurysmal clipping 17 DISCUSSION The etiology of CSDH is not completely elucidated. Dural inflammation theory, injury theory and osmotic pressure theory have all been proposed for the development of CSDH -. At present, injury theory is the most widely accepted. After mild head injury, tearing of the arachnoid membrane takes place and subarachnoid bleeding occurs due to the stretching of the bridging veins. This might be the initial factor in the formation of CSDH. The leakage of cerebrospinal fluid CSF through the arachnoid tear with blood clot stimulates the formation of reactive granulation tissue and results in the formation of a fibrous membrane outer membrane under the dura mater. This membrane is encapsulated in the subdural space and forms the outer and inner membrane of the CSDH. The outer membrane is composed of many capillaries and sinusoids. Bleeding occurs repeatedly from capillaries of the outer membrane. The degenerated endothelium in the outer membrane is accompanied by local hyperfibrinolysis. Once a closed cavity with the outer and inner membrane is formed, CSF can easily get into the hematoma cavity due to osmolar difference, through the inner membrane and arachnoid membrane. The hematoma is enlarged due to bleeding from the outer membrane and incurrent mechanisms of the cerebrospinal fluid from the inner membrane,,,. CSDH after craniotomy have been reported sporadically. Occurrence is rare, with an incidence of -,,,. Mori et al. reported that the incidence of postoperative SFC is highest after aneurysmal surgery. The incidence of CSDH requiring evacuation surgery after clipping is reported in - of cases -,. We reviewed cases requiring surgery for CSDH among cases of aneurysmal clipping, and we identified the incidence as cases. We did not find any significant difference in the incidence of CSDH according to aneurysmal site. It is known that clipping for the A-com.A aneurysm requires longer operation time than that for the MCA aneurysm. Thus, operation time does not seem to affect the incidence of postoperative CSDH. We identified the risk factors as advanced age and male gender. This is in accordance with the risk factors for CSDH generally. Various factors are thought to affect the development of postoperative CSDH formation. In aneurysmal clipping, the arachnoid membrane is dissected. Koizumi et. al said that communication between the subdural space and CSF space was an important factor in generating postoperative SFC. In addition a small amount of blood from surgery mixed with CSF is known to form a new membrane by stimulating a reaction from the dura mater, -. As far as traumatic CSDH and postoperative CSDH are concerned, the process of the CSDH formation is approximately the same. Therefore, the risk factor for CSDH formation must also be similar. There are some reports that arachnoid plasty can reduce postoperarive SFC,. We did not perform any arachnoid plasty. The procedure may be effective in preventing postoperative CSDH, but

6 18 T. Ohno, et al. the incidence of CSDH after arachnoid plasty has not yet been reported. We focused on the increase in SFC after clipping surgery. An increase in SFC was associated with the onset of CSDH. An increase of SFC over week postoperatively has also been shown to be a significant risk factor for CSDH p. Yamada et. al reported an increase in post-traumatic SFC. According to their report, in of cases, SFC was recognized within a week, and in the remaining cases, SFC was noted within two weeks. CONCLUSION This study showed that advanced age and male gender were significant factors affecting the formation of postoperative CSDH. The incidence rate of postoperative CSDH requiring surgery was. We suggest that an increase of SFC over week postoperatively can be a factor predicting CSDH after clipping. REFERENCES Koizumi H, Fukamachi A, Nukui H: Postoperative subdural fluid collections in neurosurgery. Surg Neurol ; : - Mori K, Maeda M: Risk factors for the occurrence of chronic subdural haematomas after neurosurgical procedures. Acta Neurochir ; : - Tanaka Y, Mizuno M, Kobayashi S, Sugita K: Subdural fluid collection following craniotomy. Surg Neurol ; : - Kawakami Y, Chikama M, Tamiya T, Shimamura Y: Coagulation and fibrinolysis in chronic subdural hematoma. Neurosurgery ; : - Murakami H, Hirose Y, Sagoh M, Shimizu K, Kojima M, Gotoh K, et al: Why do chronic subdural hematomas continue to grow slowly and not coagulate? Role of thrombomodulin in the mechanism. J Neurosurg ; : - Yamashima T, Yamamoto S, Friede RL: The role of endothelial gap junctions in the enlargement of chronic subdural hematomas. J neurosurg ; : - Hasegawa M, Yamashita T, Yamashita J, Suzuki M, Shimada S: Traumatic subdural hygroma: pathology and meningeal enhancement on magnetic resonance imaging. Neurosurgery ; : - Mori K, Maeda M: Surgical treatment of chronic subdural hematoma in consecutive cases: clinical characteristics, surgical outcome, complication, and recurrence rate. Neurol Med Chir Tokyo ; : - Komatsu S, Takaku A, Hori S: Three cases of chronic subdural hematoma developing after direct aneurysmal surgery. No Shinkei Geka ; : - Jpn Takahashi Y, Ohkura A, Sugita S, Miyagi J, Shigemori M: Postoperative chronic subdural hematoma following craniotomy. Four case reports. Neurol Med Chir Tokyo ; : - Friede RL, Schachenmayr M: The origin of subdural neomembranes. Fine structure of neomembranes. Am J Pathol ; : - Schachenmayr W, Friede RL: The origin of subdural neomembranes I. Fine structure of the dura-arachnoid interface in man. Am J Pathol ; : -

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8 20 T. Ohno, et al.