Meningiomas are the second most common intracranial benign tumors and represent about 15%-24% of primary brain tumors.1 Most meningiomas grow slowly at a rate of only 2.4 mm annually.2 Due to their slow growth, few clinical symptoms occur until the tumor reaches a large size. If the meningioma grows at the front or rear of the cranial cavity, it can grow to be very large before that area’s vital functions are affected. Therefore, giant meningiomas are not infrequent, and actually account for 11.9% of meningiomas in our hospital. Because the volume of the giant meningioma is large, resection is usually difficult and often accompanied by more damaging operative wounds. In addition, serious postoperative complications can ensue, including acute subdural hematoma, acute cerebral edema, brain infarction and remote extradural hematoma. To reduce these complications, we usually perform operations using different surgical approaches according to the conditions and tumor anatomy of the individual patient. Meticulous hemostasis, as well as sufficient drainage, is also applied, however, surgical outcomes remain largely unsatisfactory. In the present study, we introduced a new technique to prevent postoperative complications following the resection of giant meningiomas. A liquid capsule was placed in the remnant cavity after tumor resection, followed by gradual withdrawal of the liquid inside the capsule. From May 2005 to December 2006, we applied this technique in 26 patients and the results indicate that liquid capsule application can effectively decrease the incidence of postoperative complications after the resection of a giant meningioma. CLINICAL DATA Patients In this series, there were 16 male and 10 female patients with an average age of 55 (ranged 37-70) years. The duration of disease ranged from 6 months to 8 years. Among them, 18 patients had headache and vomiting, 3 had blurred vision, 3 had unsteadily walking; 1 experienced acoustical disturbances, 1 had facial numbness, 1 suffered psychological disorders and 1 exhibited speech dullness. Imaging findings and classification All patients underwent head computerized tomography (CT) and/or magnetic resonance imaging (MRI) examinations prior to surgery. By unenhanced CT scan, tumors appeared as high-density or relatively high-density images. On MRI, the lesions were typically hypo-to isointense on T1 weighted images (Figure 1) and iso- to hyperintense on T2-weighted images. After intravenous injection of Gd-DTPA (gadolinium diethylene triamine pentaacetate) the tumors showed homogeneous enhancement with clear boundaries, as well as a dural “tail sign” by MRI (Figure 2). The regions surrounding the tumors often demonstrated varying degrees of edema on MRI when the tumors were located at the hemicerebrum. The anatomical locations of the meningioma in these 26 cases were as follows: 22 were supratentorial, including 9 at the cerebral convexity, 4 in the parasagittal sinus, 3 in the cerebral falx, 2 at the trigone of the lateral ventricle, 2 in the olfactory groove, 1 on the sphenoid ridge and 1 in the posterior cranial fossa. The diameters of these meningiomas ranged from 7.0 to 12.5 cm. The other 4 cases were located inferior to the tentorium, including 2 on the vermis cerebellum, 1 on the tentorium and 1 at the cerebellopontine angle. The diameters of these tumors ranged from 5 to 8 cm.Figure 1.: An image from a 37 years old woman with headaches for 3 months shows a giant meningioma with a maximum diameter of 7.5 cm was observed in the posterior cranial fossa on T1-weighted MR images.Figure 2.: The tumor showed homogeneous enhancement with clear boundaries after intravenous injection of Gd-DTPA.Management and procedure We performed operations on all of these 26 patients using surgical approaches appropriate to the location of the tumor. After the tumor was resected, a double-channel Foley catheter (22Fr/Ch, 50 CC, KeLong Medical, China) was placed into the remnant cavity (Figure 3). Prior to being inserted into the cavity, the top canal was cut carefully (Figure 4), followed by the injection of 15-50 ml of normal saline into the capsule. The amount of normal saline injected was determined based on the size of the remnant cavity. Using this approach, the brain tissue was kept as close to its pre-operative position as possible. To prevent the liquid capsule from touching the cavity, gelatin sponges were placed surrounding the capsule. Finally, a normal drainage tube from the cavity to another outlet was placed in the skin. The routine procedures for sewing the dura and closing the skull were used afterwards. Twenty-four hours after the operation, a skull CT was taken to review the status of the brain (Figure 5). About 10 ml of saline were withdrawn every day for 3-5 days, at which point the capsule was empty and removed (Figure 6).Figure 3.: A liquid capsule was set in the remnant cavity at the end of the operation. There was about 25 ml of normal saline in this capsule.Figure 4.: Before inserting the liquid capsule into the remnant cavity, the top canal of the capsule (arrow) was cut. (A) A liquid capsule before the top canal was cut. (B) After the top canal was cut.Figure 5.: CT image of one day after the operation shows the liquid capsule was clearly seen in the remnant cavity.Figure 6.: Postoperative four days later the liquid capsule had been removed. No blood or effusion was observed in the CT image.Application of liquid capsule According to Simpson’s standard classification for meningiomas,3 the 26 cases were categorized into three grades; 16 of grade I, 9 of grade II and 1 of grade III tumors. All the patients survived and recovered after the operation. Twenty-three patients recovered well without any postoperative complications. One patient experienced an epidural hematoma at a remote site on postoperative day 2, at which point, we immediately removed the liquid capsule and initiated treatment with trepanation and urokinase. The hematoma disappeared four days later. When investigating the cause of the epidural hematoma in this case, we found that the liquid capsule used was too small to match the remnant cavity, indicating that an insufficient liquid capsule was probably the cause of the patient’s hematoma. Two patients experienced cerebroventricular hemorrhage because the remnant cavity communicated with the cerebral ventricle. In one of these cases, the tumor was supratentorial while the other was inferior to the tentorium. The blood was removed by releasing the cerebrospinal fluid via lumbar puncture. Postoperative pathological data showed that all cases were grade I according to the World Health Organization classification, including 11 cases of meningothelial type, 7 of fibroblastic type, 5 of psammomatous type, 2 of angiomatous type and 1 of transitional (mixed) type. DISCUSSION Recent advancements in microneurosurgical techniques as well as skull base surgical approaches have led to improved outcomes after meningioma resection, however, a significant mortality still exists.4 Statistical analysis demonstrates that cerebral hemorrhage is the main cause of death in patients following meningioma resection.5 According to our clinical data, the most common postoperative complications after giant meningioma resection can be categorized as follows: acute subdural hematoma, acute cerebral edema, ischemic brain infarction and remote extradural hematoma. Neurosurgeons have made many contributions to help decrease the incidence of postoperative complications from giant meningiomas. Tan et al6 have reported that by applying intra-capsular removal techniques during surgery on giant meningiomas, a larger volume of the tumor can be resected while greatly reducing operative damage to the brain. Hirohata et al7 used preoperative embolization methods to reduce bleeding during operation. These methods greatly reduced operative damage to the brain to some degree, but the root cause of postoperative complications has not been eliminated. Following the creation of a large remnant cavity after tumor resection, the sudden changes in anatomic structures will also be accompanied by pathophysiological changes. Therefore, eliminating the remnant cavity is critical for reducing postoperative complications. In this study, throughout our one-year clinical review, we used a liquid capsule to fill the remnant cavity after tumor resection and emptied the liquid gradually, depending on the situation of the patients. Our results showed that liquid capsule application effectively decreases the incidence of postoperative complications. The advantages of setting a liquid capsule into the remnant cavity after meningioma resection can be summarized as follows. First, the capsule holds the collapsed brain tissue in its preoperative position, and can thereby prevent the shearing of the bridging veins. Similarly, the capsule prevents surrounding arteries and veins from deforming and twisting by minimizing movement of the brain tissue after resection. Second, with a liquid capsule inside the remnant cavity, the intracranial pressure can be reduced gradually to prevent the remote dura mater from peeling off. Third, the liquid capsule can also maintain the position of the brain tissue surrounding the remnant cavity with a relative tensile force; this can reduce the occurrence of acute brain edema and functional disturbances caused by the breakthrough of perfusion pressure. Fourth, the liquid capsule can press on the wall of the remnant cavity and reduce both the effusion of tissue fluid and capillary hemorrhage to prevent hematoma formation. Fifth, the liquid capsule can also serve as a drainage system. Conventionally, because the dura mater is sewn very tightly after resection, the effusion gathers in the remnant cavity and becomes difficult to absorb, possibly resulting in a hematoma. By applying the liquid capsule with a drainage tube at its center, effusions can be easily drained. In the patients we studied in this series, all recovered well without serious complications or adverse effects. Their clinical symptoms also improved to different degrees compared to their preoperative symptoms. The double-channel Foley catheter used in our study is a siliconized and disposable product that is biocompatible and relatively less irritating to the human body. Therefore, it can be placed in the body without any adverse reactions. Besides, it is soft and easy to place during the surgery. The type of catheter we used was an Fr22-50 milliliter. Through clinical testing, we found that the capsule shrank after draining out all the normal saline within 7 days, and that it could be easily withdrawn from the cranial cavity. In our 26 patients, no side effects were related to the application of the liquid capsule. There are several important points to keep in mind when considering use of the liquid capsule. First, the size of capsule should be adjusted to fit the remnant cavity in order to maintain optimal positioning of the brain tissue. If the capsule is too large, it will apply excessive pressure to the surrounding brain tissue; if the capsule is too small, it will not be sufficient to stabilize the brain architecture. Second, the liquid in the capsule should not be retained in the brain for a long period and should be removed gradually over the first 3 to 5 postoperative days. Third, placing the liquid capsule is ineffective if the meningioma surrounds the cerebral ventricle. There were two cases in our group that had cerebroventricular hemorrhage, which required evacuation of the hemorrhage by releasing cerebrospinal fluid. We think that these cases may have been caused by the movement of the liquid capsule inside the cavity. In summary, we conclude that placement of a liquid capsule into the remnant cavity following giant meningioma resection could effectively prevent some serious postoperative complications, such as brain hemorrhage, brain edema, and cerebral infarction. This provides a novel approach for the treatment of giant meningioma, as well as for the prevention and cure of postoperative complications in other giant intracranial tumors.