Chen Lihua.et al. Vestibular schwannoma microsurgery with special reference to facial nerve preservation. Clinical Neurology and Neurosurgery, 2009,111:47–53Vestibular Schwannoma Microsurgery with Special Reference to Facial Nerve PreservationChen Lihua, Chen Ling, Ling Feng. Department of Neurosurgery, Xuanwu Hospital, The Capital University of Medical Science, Chuangchu street 45, Beijing 100053, ChinaYuan Xianrui,Fang Jiasheng, Liu Yunsheng. Department of Neurosurgery , Xiangya Hospital , Central South University , Changsha 410008 China.AbstractObjectives: To study retrospectively the outcomes of vestibular schwannoma (VS) removal, and to present microsurgical techique with special reference to facial nerve preservation. Methods:The study comprised 103 consecutive patients who had undergoneVS removal from January 2003 to December 2006. The patients were operated on by a retrosigmoid, transmeatal approach. Tumors were categorized into 3 groups according to the diameters at the cerebellopontine angle. Medical records, operation summaries, follow-up data, and neuroradiological findings were analyzed. The main outcome measures included MRIs, neurological status, patient’s perspective, and surgical complications. The authors studied the relationships between tumor size, location, and topography relative to the facial nerve bundles to determine how tumor characteristics influence facial nerve preservation. The follow-up had a mean duration of 16 months and ranged from 3 to 39 months. Facial nerve function was assesssed by House–Brackmann grading starting from 3 months after operation so as to allow for adequate facial nerve recovery. Results: Of 103 cases operated by the retrosigmoid transmeatal approach, 101 (98.1%) had complete tumor removal and had anatomic preservation of the facial nerve as well, and 2 had subtotal removal with disruption of nerve continuity.Postoperatively, of the 18 cases in group I (small) and the 46 cases in group II (medium-sized), all had anatomic preservation of the facial nerve; of the 39 cases in group III (large), 2 cases suffered nerve discontinuity, and underwent immediate nerve reconstruction. Postoperative evaluation of facial nerve function revealed excellent results (Grade I or II) in 100% of small tumors, in 89.1% of medium-sized tumors, and in 69.2% of large tumors. Overall 83.5% of patients had normal or near normal (Grade I or II) facial nerve function 3 months to 1 year after tumor removal. The facial nerve was most commonly located on the anterior middle third of the tumor capsule, regardless of tumor size (51 cases, 49.5%); it was on the anterior superior aspect in 24 cases (23.3%), and anterior inferior aspect in 21 cases (20.4%). The most frequent postoperative complications were headache, cerebellar edema, and dizziness, which occurred in 11, 3, and 4 patients respectively. There was no surgery-related permanent complications, or morbidity due to intraoperative air embolism. The mortality rate was 0%. Conclusions: Postoperative facial function is intimately correlated with tumor size. The removal of the posterior meatal wall is important for achieving anatomic preservation of the structures adjacent to the tumor. The goal of VS treatment should be complete tumor excision in one stage, low morbidity, and maintenance of normal facial nerve function. This goal can be attained with the retrosigmoid transmeatal approach, refined microsurgical technique, and intraoperative facial nerve monitoring.Key words: vestibular schwannoma; retrosigmoid transmeatal approach; nerve monitoring; facial nerve function.IntroductionAlthough VSs are benign tumors characterized by slow growth, they may erode the internal auditory canal and compress adjacent cranial nerves. Total tumor removal and a good quality of life, defined as preservation of facial function and hearing have become the generally accepted treatment goals. Increasing expectations have paralleled improvements in surgical techniques, and the introduction of intraoperative facial nerve monitoring[1]. Anatomical and functional preservation of the facial nerve have become routine in experienced hands[2]. Although many authors report increasing rates of facial nerve preservation after surgery for VSs, paralysis is still a major concern. Advances in neuroimaging, intraoperative nerve monitoring, and microsurgical technique have transformed a once highly dangerous operation into one with low morbidity and mortality, and shifted the focus of VS surgery from prolonging life to preserving nerve function, with modern series reporting up to 90% of patients having facial nerve function that is normal or near-normal postoperatively [3]. During the past 4 years, the retrosigmoid transmeatal approach and a standardized microsurgical technique have been used for resecting 103 VSs by the authors. In this study we review our results and discuss various issues, including the different anatomical locations of the facial nerve in relation to the the tumor capsule in the cerebellar-pontine angle (CPA), surgical technique, patient positioning, and ways to protect the facial nerve.Clinical Materials and MethodsGeneral We performed a retrospective study on 103 consecutive patients with VSs including 2 cases of neurofibromatosis-2 (NF-2) with bilateral VSs, treated from January 2003 to Decmber 2006, using standardized microsurgical technique and the suboccipital retrosigmoid transmeatal approach. Our series consists of 58 female and 45 male patients treated at Xiangya hospital and Xuanwu hospital. Patient age ranged from 19 to 76 years, with an average of 45.1 years. All preoperative, intraoperative and postoperative records, neuroradiological findings and follow-up data were analyzed, including CTs, MRIs, pure tone audiograms, speech discrimination tests, brainstem auditory evoked potentials (BAEP) recordings, intraoperative videotapes, topographic relationship of the tumor to the surrounding nerve bundles. Adherence of cranial nerves and blood vessels to tumor capsule was distinguished from mere contact by the necessity for surgical manipulation or dissection to free them from the capsule; neurovascular structures without actual adherence to the tumor were not documented. The exact anatomical location of the facial and cochlear nerves on the tumor capsule was noted, and was described in terms of the anterior, posterior, upper or lower pole. The anterior and posterior locations were further defined in terms of the upper, middle, or lower third of the tumor. The type of cranial nerve location was confirmed by intraoperative monitoring of the facial nerve by EMG or BAEP, whenever possible.Symptoms and signsThe most common initial symptoms included hearing loss and tinnitus, followed by vertigo, dizziness, and unstable gait. The time lapse from initial symptoms to tumor diagnosis varied from 2 months to 9 years. Symptoms developed in the following sequence: cochlear nerve dysfunction initially, vestibular disturbances next, and then trigeminal dysfunction; trigeminal disturbances were particularly prominent in large tumors with brain stem compression. The most frequent symptoms and signs in our 103 patients were the following: hearing disturbance in 96 cases, including complete hearing loss in 25; vestibular disturbance, such as tinnitus and vertigo in 74; headache and dizziness in 32; gait instability and cerebellar ataxia in 29; trigeminal neuralgia and abnormal corneal response, facial hypesthesia or anesthesia in 17; facial nerve weakness and taste abnormality in 13; and swallowing disturbance in 15. Symptom incidence and duration did not strictly correlate with tumor size, except for trigeminal nerve symptoms whose duration correlated more closely with tumor size. Detection of taste disturbance was useful because it indicated an increased risk of facial paresis.Preoperation examination and evaluationAll of the patients were prepared for surgery by a thorough clinical evaluation, which included otorhinolaryngological investigations, CTs with bone windows, MRIs, functional x-rays of the cervical spine, and audiometric tests. Preoperative CTs with bone windows could depict clearly the semicircular canals, jugular bulb, and other petrous bone structures. Anatomic relations between the labyrinth and the IAM could be evaluated pre- and postoperatively by CTs. The vestibule and the common crus were the organs most frequently identified at the level of the IAM in preoperative CTs; the vestibule, common crus, anterior semicircular canal (SCC), posterior SCC, and superior SCC were also usually observed. The location of the labyrinth was classified into three types in relation to the sigmoid-fundus line (S-F line, a virtual line that connects the fundus of the IAM and the medial border of the sigmoid sinus) as follows: lateral type, both the vestibule and the common crus were lateral to the S-F line; line type, either one of them was on the S-F line; or medial type, both or either one of them was medial to the line. If the posterior semicircular canal and the crus commune were located lateral to S-F line, there was no risk of injuring them. If these structures were medial to this line, they were in danger of being opened. Preoperative CT scans were used for anatomic landmark orientation. The extent of bone removal from the posterior wall of the IAM was evaluated by postoperative CTs. A high jugular bulb was noted in five cases.Tumor size and locationTumors ranged in size from 1.5 to 6.7 cm in diameter, with the mean being 3.8 cm. Thirty-one tumors were substantially cystic. Cystic formation is important to notice, because it predisposes to complications of the facial nerve, postoperative hemorrhage, and operative difficulties, arising from adherence, hemorrhagic nature, and lack of capsule. To facilitate data analysis and elucidate relationship between tumor size and neurovascular structure involvement with the tumor capsule, the patients were divided into three groups according to the maximal extrameatal diameter (the largest dimension measured medial to the plane of the porus acousticus, thus excluding the intracanalicular dimensions) found on magnetic resonance imaging in the axial plane; intra- and extrameatal tumor extension was also considered. Group I: small tumor (<2.5cm, including totally intracanalicular lesions), 18 cases. Group II: medium-sized tumor (2.5-3.9 cm), 46 cases. Group III: large tumor(≥4 cm), 39 cases.Operation methodsApproach and positioningFifty-eight patients were operated on in a semi-seated position, and 45 in lateral, modified Sugita position, via a lateral suboccipital, retrosigmoid, transmeatal approach. If the tumor was large, a lateral decubitus position was used. The lateral cerebellomedullary cistern was opened prior to dural opening, for withdrawal of a small amount of CSF. In the semi-sitting position, the patient's head and neck was slightly flexed,tilted and rotated 20 to 30 degrees to the ipsilateral side, and the legs were elevated to the level of the right cardiac atrium. All body parts susceptible to pressure were supported with cushions. The advantages of the semi-sitting position is that it facilitates control of intracranial pressure by better drainage of CSF from the cisterns, and improves exposure.Intraoperative monitoringIntraoperative monitoring included ECG, continuous measurement of arterial blood pressure and superior vena cava pressure. The tip of the central venous catheter must be located within the right atrium to aspirate any invaded air that might cause embolism. Continuous measurement of the end-expiratory CO2 concentration, and the arterial oxygen saturation were also performed. For early recognition of air embolism, precordial Doppler ultrasonography was done. BAEPs were assessed to monitor acoustic nerve function. EMG recordings of the orbicularis oris and oculi muscles were used to monitor facial nerve function. Anatomical preservation of the facial nerve was assessed using both visualization and electrical stimulation of the facial nerve, proximally at its brainstem origin, and distally in the IAM. A bipolar stimulus with an intensity of 1 mA and a duration of 0.1 msec was used to assess facial nerve response. Facial nerve and BAEP monitoring was used in all cases. All parts of the facial nerve were identified via constant EMG recording connected to loudspeakers. After tumor resection, the continuity of the facial nerve was confirmed by gently touching or electrically stimulating the nerve from the brainstem to the intrameatal part. When performing the following manipulations, such as, drilling the meatus, manipulating the tumor, using bipolar coagulation, or directly moving the nerve, electro-monitoring provided feedback to the surgeon, who then could adjust his microsurgical maneuvers accordingly. Since stimulating the facial nerve intraoperatively identified its exact location within the CPA, we preferred to use the facial nerve stimulator during dissection to obtain real-time EMG recordings from time to time.Navigational guidanceWe investigated the usefulness of a microscope-based navigation system (Zeiss, NC-4) in conjunction with a neuronavigational system (BrainLab) based on three-dimensional volumetric imaging for the removal of the posterior wall of the IAM, and used this method in 9 patients for opening the IAC and localizing the transverse sinus and sigmoid sinus. This navigation system allowed the transverse and sigmoid sinuses to be visualized in correlation with bony landmarks, such as the asterion, and enabled performing a rapid and safe craniotomy, besides avoiding opening of the sigmoid and transverse sinuses, thereby avoiding air embolism. A real-time display of structural contours, distance between the focal point and target point, and three-dimensional position was available. For each target structure, the coordinates based on the radiological images (CT, MRI and MRV) were compared with the coordinates provided by direct in situ microscopic focusing on the target.Retrosigmoid craniotomyA part of the suboccipital skin was marked by a vertical incision or small “S”-shaped incision, 5 to 7 cm in length. A suboccipital craniectomy was performed extending to the posterior margin of the sigmoid sinus and exposing the inferior margin of the transverse sinus. The splenius capitis, semispinalis capitis, and levator scapulae muscles were detached from their bone attachments. A burr hole was initiated near the asterion supra-anteriorly, then a bone flap was cut toward the posterior and inferior aspect of the mastoid process; the entire retrosigmoid dura was separated from the bone and the field was enlarged with drilling to form a cranioplasty of approximately 2 × 3 to 3 × 3.5 cm, exposing the posterior edge of the sigmoid sinus and the sigmoid-transverse junction. The dura was opened along the transverse and sigmoid sinuses, to form an arc-like dural incision convexed laterally. Special attention was given to the emissary veins and bridging veins to reduce the risks of postoperative sinus thrombosis, hemorrhage, and brainstem edema.Surgical techniqueTumor exposureAfter performing a laterally convexed incision of the dura, the cerebellomedullary cistern was opened to facilitate drainage of CSF, while waiting for spontaneous cerebellar retraction. The cerebellum was mildly retracted to gain visibility of the posterior wall of the IAM, and possibly a part of the tumor, and the brain stem too.The drilling of posterior wall of the IAC and removal of tumor in the IACIntraoperatively, we used the following technique to approach the intracanalicular tumor portion. The dura from the posterior IAM was removed, and drilled away with a high-speed diamond burr under continuous saline solution irrigation until the intrameatal tumor extension was exposed. In the drilling process, it should be noted that identification of the posterior margin of the posterior meatal lip as a landmark was difficult in patients with a funnel-shaped deformity of the IAM, and that heat and vibration damage during drilling might contribute to postoperative hearing deterioration. In addition, injury to the ES and ED might also be a cause of hearing loss, so care should be taken at each step of the removal of the posterior meatal wall. The drilling of the posterior wall of the IAM must be sufficient so as to achieve complete removal of intrameatal tumor, especially if the tumor had reached such a size as to partially cover the petrous bone in a manner that prohibited opening of the IAM without exceeding the recommended degree of retraction of the tumor and the cerebellum. The depth of the remaining IAM was repeatedly assessed by palpating the fundus with a micro nerve hook. The most lateral tumor portion was carefully mobilized out of the IAM with a microdissector, and the cranial nerves VII and VIII at the fundus were identified. Once the facial and vestibulocochlear nerves were exposed, the tumor was resected piecemeal on the arachnoid plane.Dissection on arachnoid planeVSs represent a heterogeneous group of tumors in terms of their consistency, existence of a capsule and presence of an arachnoid plane between the tumor and the brain. Treatment strategy should be individualized according to those characteristics. Initial exenteration and subsequent tumor removal by working around the tumor on the arachnoid plane was not possible in all cases. If the arachnoid plane was not well developed, dissection by gripping the arachnoid sheath with two forceps and carefully stripping it from the capsule was not applicable, in which case each layer of the schwannoma was successively removed piecemeal, from the inner to the outer layer until the outermost layer was reached. Careful dissection required prolonged operative time but allowed for superior preservation of cochlear and facial nerve integrity. We found that the trigeminal nerve was adherent to the tumor capsule in a minority of cases, and that even if postoperative dysfunction could happen, the loss of facial sensation was minor and usually well tolerated. In our experience, the trochlear and hypoglossal nerves associated with larger VSs usually could be dissected free of the tumor capsule anatomically intact, and significant postoperative dysfunction did not occur.Tumor removal in the CPAThe extrameatal intracapsular tumor was debulked whenever possible with the Cavitron ultrasonic surgical aspirator (CUSA), so as to reduce the pressure to the surrounding nervous and vascular structures. The CUSA helped to define and maintain the surgical plane between the tumor and the cerebellum, brainstem and cranial nerves. The tumor was dissected from the surrounding neural and vascular structures by gripping the tumor capsule and dissecting on the arachnoid plane. With tumors of normal consistency, the mobilization started in the IAM, followed by resection of the extrameatal portion. If the tumor was very hard, primary mobilization in the IAM might be impossible, and enucleation of the tumor in the IAM or extrameatal area had to be done. Under continuous saline irrigation, the nerves were carefully mobilized. Bipolar coagulation was used minimally and reserved as final hemostatic measure at the end of surgery, to ensure maximal blood supply to the brain stem and other neural structures. When the bulk of the tumor was removed, compression by the tumor on neural structures would diminish. The final liberation of neural structures was performed by tightly gripping the arachnoid sheath with forceps and avoiding overstretching. Modulating the directions of microsurgical maneuvers favored the recovery of nerve fibers from the manipulations. By gently pulling the remaining tumor mass medially and upward, the lower and lateral parts could be visualized and dissected, often from the intrameatal side. Removal of the tumor portion at the entrance of the IAM was postponed to the end of surgery. Because the connection between the tumor and the nerves was firmest at the entrance of the IAC, it was often necessary to separate them by sharp dissection. No permanent cure was available for NF-2, because its biological characteristic significantly diminished the chances for complete tumor removal and intact neural function; hence, brainstem decompression and causing the least harm to cranial nerve function were the main goals. Constant irrigation, done by an assistant, provided a clear view of the surgical field. Whenever possible, the petrosal veins were preserved.Protecting blood supply to brain stem and other neural structures To prevent disturbance of blood circulation to the nerves, dissection on the subarachnoid space is recommended. For safety to the brain stem, dissection under continuous irrigation is especially helpful, because cauterization is reduced to a minimum. Identification and control of the vascular supply to the brain stem is optimal by the retrosigmoid transmeatal approach.Nerve dissection and preservationTrigeminal and cochlear nerve nerve dissection and preservationSurgical manipulation of the trigeminal nerve may lead to bradycardia, as well as arterial hypotension, a phenomenon described as the trigeminocardiac reflex. Gentle and smooth manipulations in the region of the trigeminal nerve, and avoidance of traction have proved to be most important in diminishing the trigeminocardiac reflex. Immediately this reflex occurs, the surgeon should stop the triggering maneuvers. The cochlear nerve has less anatomical variation than the facial nerve and is most frequently found in the anterior inferior portion of the tumor capsule. It is best identified on the medial aspect of the tumor capsule lying on the brainstem surface. Attempts should then be made to identify the nerve in the IAM, where its location is anterior and below the transverse crest, and finally to follow the nerve along the inferior portion of the tumor capsule. We have shown that it is exceedingly rare that the cochlear nerve passes through the tumor itself. In our experience, we find that preservation of functional hearing is a realistic goal even in patients with large tumors, and a very adherent cochlear nerve that requires painstaking dissection and monitoring with intraoperative BAEPs.Identification of the facial nerve Our technique of facial nerve preservation is based on familiarity with anatomic landmarks and intraoperative facial nerve monitoring. The facial nerve is identified both medial and lateral to the tumor before dissecting the tumor capsule from the intervening segment of the nerve. The nerve is identified lateral to the tumor after removal of the posterior wall of the IAM as it passes above the transverse crest and behind the vertical crest in the anterosuperior quadrant of the meatus. It is identified at the brain stem as the tumor capsule is being removed from the brain stem on the basis of three landmarks. The first is the pontomedullary sulcus. The facial nerve exits at the lateral end of the pontomedullary sulcus. The second is related to a line drawn along the posterior margin of the inferior olive at the site where the glossopharyngeal, vagus, and accessory nerves enter the brain stem. These nerves are usually seen below the tumor during the early stages of tumor removal. The facial nerve arises from the brain stem 2 or 3 mm above the line where the glossopharyngeal nerve enters the brain stem. The third is related to the flocculus, which attaches to the brain stem along the margin of the lateral recess of the fourth ventricle, and the choroid plexus which protrudes from the foramen of Luschka behind the IXth and Xth cranial nerves. The eight nerve, which is located just behind the facial nerve at the lateral end of the pontomedullary sulcus, joins the brain stem in front of the site of attachment to the flocculus, the margin of the foramen of Luschka and the lateral recess of the fourth ventricle. The choroid plexus protruding from the foramen of Luschka sits on the posterior surface of the ninth and tenth nerves, just behind and below where the facial nerve enters the brain stem. The use of these anatomic landmarks at the brain stem medial to the tumor and within the meatus lateral to the tumor, in combination with facial nerve monitoring, will assist in preserving the facial nerve during tumor removal. We think that anatomic preservation of the bundles of the eighth cranial nerve, even when they cannot be functionally preserved, acts as a protective barrier, frequently protecting the facial nerve in the interval between the brain stem and the meatus.Facial nerve preservationThe facial nerve was identified with the aid of a surgical microscope in the lateral portion of the IAM after dural opening. Early identification of the facial nerve medially facilitated continued medial-to-lateral dissection of the tumor from the nerve and other neural structures. Facial nerve stimulation-monitoring was performed, whenever further visualization of the nerve at different angles was necessary. Once the tumor had been completely removed, the facial nerve was routinely stimulated at its root, most proximal to the brainstem. If no response was obtained, the stimulus intensity was increased by 0.1-mA increments until a response was obtained. If the intensity was increased to 0.4 mA, yet no response was obtained, the facial nerve was tested again throughout its course to the lateral IAM to determine the site of injury. In 2 cases, the facial nerve was invaded by a tumor, such that the nerve diverged into several fascicles and intermingled with the tumor, so the nerve was sacrificed to ensure a complete resection. The facial nerve could be involved with the tumor, either by passing through it, or being infiltrated by it. After tumor removal, the ends of the severed nerve were immediately sutured together with 10-0 nylon in an end-to-end fashion.Preservation of the nerve was attempted for all patients by using a special microsurgical technique. Intraoperative monitoring was performed on the patient, who was anesthetized with or without a mild relaxant medication. After opening the IAM, the intrameatal tumor extension was inspected and the position of the seventh and eighth nerves was determined by their electrophysiological response. The extrameatal tumor mass was reduced by tumor enucleation from inside, usually by using the CUSA. As soon as the compression of the tumor on the adjacent structures was reduced, dissection of the tumor from the surrounding neural and vascular structures was performed by firmly gripping the tumor capsule and dissecting on the arachnoid plane. Maximum safety to all relevant structures was thereby guaranteed. The tumor-nerve border was mobilized medially along the brain stem for identification of the proximal part of the facial nerve and its course at the upper extension of the tumor. By gripping the remnant part of the tumor and pulling it medially and upward, the lowest and most lateral aspects of the facial nerve became visible. This part could usually be dissected free by mobilizing the intrameatal portion laterally toward the extrameatal portion, and by repeatedly moving the dissector in the interspace between the tumor and the nerves. Continuous electromyographic recording provided the feedback for identifying all the segments of the facial nerve. Nerve continuity could be confirmed by light touching or by electrical stimulation of the nerve.ClosureJugular venous compression was performed at the end of the procedure to make any open or torn veins visible for final hemostasis. A piece of free fat or muscle graft fixed with fibrin glue was placed over the drilled region to occlude the opened air cells in the region of the IAM and prevent the formation of an intradural CSF fistula. After the retractor was removed and the cerebellum reexpanded, continuous watertight dural closure with bone wax and muscle flap was used to close the opened mastoid cells of the occipital bone. The bone flap was laid back and fixed with titanium peg, and if there was a large bone defect, a cranioplasty was performed with titanium microplates to prevent the occurrence of persistent postoperative headache and subcutaneous hydrops.Postoperative care and follow-up Postoperative care included on average one day’s stay in an intensive care unit. Contrast-enhanced MRI must be performed within 3 days of operation. Audiometry and CT with bony window were performed 1 week after surgery. Estimation of outcome was based primarily on the surgeon’s perspective. We assessed the following outcome measures: completeness of tumor resection, facial nerve electrophysiological activity, responses at the end of the operation and postoperative function. Data used for evaluation also included signs and symptoms, audiograms, imaging materials, and questionnaires. All of our patients were evaluated with follow-up MRI / CT from 3 months to 1 year after operation, with MRI being used preferentially, and then once every 1 or 2 years depending on the patient's cooperation. The mean follow-up duration was 16 months (range 3–39 months). For evaluation we checked for facial symmetry at rest and on motion, separate movements of all three segments (forehead, eyes, mouth), and incidence of conjunctivitis and synkinesias, then graded the results by the H-B scale. If the patient could not come to hospital, a questionnaire was mailed to him/her 1 year postoperatively, interrogating on his/her perception of the functional outcome, as compared to the clinician’s observation.Statistical analysisThe following statistical values were obtained: mean, maximum, and minimum values. The following parameters were analyzed: facial nerve function, tumor size. Statistical evaluation included Student’s t test. P values less than 0.05 were considered significant.ResultsWe hold that facial nerve preservation and total tumor removal took precedence over hearing preservation. All three goals (complete removal, preservation of facial and hearing functions) were achieved in 13 cases. There was no postoperative morbidity due to intraoperative air embolism. The mortality rate in our series was 0%. The trigeminal pain resolved in all patients. According to the length of the remaining posterior wall of the IAM, as determined by postoperative CT, the patients were divided into the partially resected group (n =48) and the widely opened IAM group (n = 55), the mean length of the posterior wall at the fundus was shortened to 4.6 ± 1.0 mm and to 1.9 ± 0.5 mm (n = 55), respectively. The location of the labyrinth determined by preoperative CT was lateral in 52 cases, medial in 28 cases, and on the SF-line in 23 cases. Resection of the posterior wall of the IAM did not extend beyond the transverse crest.Extent of Tumor ResectionOf the 103 cases of tumor removed by us, visual inspection and postoperative MR imaging showed that in 101 cases (98.1%) complete resection was achieved without tumor recurrence. The remaining 2 patients underwent intentional subtotal tumor removal, because 1 patient had NF-Ⅱ and subtotal removal was necessary to avoid facial nerve paralysis and preserve hearing in the only functional ear, and the other case showed changes in vital signs during operation, so only brain stem decompression was performed. Those two patients had large tumors severely compressing the brainstem, and we intentionally left a small part of the tumor capsule that was tightly adherent to the facial nerve to preserve its function. When the tumor adhered tightly to the facial and/or trigeminal nerve, any attempt to dissect the nerve from the tumor capsule led to intense electromyographic changes.Relationship between tumor and nerve/blood vesselThe most common location of the facial nerve was on the anterior middle third of the tumor capsule, regardless of tumor size. In our series, the facial nerve was on the anterior middle third of the tumor in 51 cases (49.5%), anterior superior aspect in 24 cases (23.3%), anterior inferior aspect in 21 cases (20.4%) (table 1). The facial nerve passed through the tumor itself in 1 patient, so that the tumor infiltrated the nerve sheath and enfolded it completely. The most common location of the eighth cranial nerve complex was the anterior inferior portion of the tumor. Not surprisingly, 39 larger tumors (Group III) invaded the fifth cranial nerve in all patients, and the 9th– 11th cranial nerve complex in 28 cases. The anterior inferior cerebellar artery (AICA) trunk and its branches was the artery that was most closely associated with VSs. Its trunk was adherent to the tumor capsule in 1 patient in Group I, 13 in Group II, and 39 (i.e., 100%) in Group III.. The AICA or its branches was noted to traverse through the tumor itself in 5 and 11 patients, in Group II and Group III respectively. The superior cerebellar artery (SCA) was frequently involved with the tumor capsule in Group III patients (31/39). The main trunk of the posterior inferior cerebellar artery (PICA) was not involved in Group I tumors, but was adherent to tumor capsules in 13 patients in Group II and 31 patients in Group III. The PICA or its branches was seen to pass into the tumor only in large tumors (Group III, 5cases). In 32 cases in Group III the vertebral artery (VA) was invaded.TABLE 1. Facial nerve location in 103 VSsTumor size anterior middle third anterior superior anterior inferior superior pole inferior pole in tumorGroup Ⅰ 13 3 2GroupⅡ 18 13 13 1 1GroupⅢ 20 8 6 4 1Total 51 24 21 1 5 1Anatomical and functional preservation of facial nerveOf the 103 cases, the facial nerve was anatomically preserved in 101 (98.1%). In group Ⅰ, it was anatomically fully preserved in 18 cases (100 %); in group II, 46 cases (100 %); in group Ⅲ the facial nerve was partially destroyed in 3 patients by dense scar tissue along the anterior surface of the tumor and just medial to the porus, and by operative manoevre in another 2 patients. End-to-end facial nerve anastomosis was performed at the CPA in those patients, and essentially satisfactory facial function of H-B Grade 3 recovery resulted one year after reconstruction.The 2 cases in which anatomical integrity was lost had cystic changes. Facial nerve functional outcome is presented in Table 2. Most patients displayed adequate facial movements, and no patient suffered complete facial nerve paralysis. Overall at the final follow-up, 83.5% patients had normal or near normal facial nerve function (Grade I or II) at 3 months to 1 year after tumor resection. Facial nerve weakness (H-B Grades III–VI) was noted in 17 cases (16.5%). No patient showed deterioration in facial nerve function in the 3 to 12 month interval between discharge and last follow-up.Table 2 facial nerve function outcome in 103 tumorsHouse-Brackmann Grade Immediately Postop. At Discharge 3 months Postop. 1 year Postop.Ⅰ 14 13 15 16Ⅱ 67 70 71 70Ⅲ 15 14 12 13Ⅳ 6 5 5 4Ⅴ 1 1 0 0Ⅵ 0 0 0 0Tumor size and facial functionPostoperative facial function was intimately correlated with tumor size. Evaluation by H-B grading revealed excellent results (Grade I or II) in 100% of small tumors within 3 months of operation; of 46 patients with medium-sized tumors, 89.1% had Grade I or II function; of 39 patients with large tumors, 69.2 % had Grade I or II result (Table 3).TABLE 3. the relationship between facial nerve function and tumor sizeTumor Preoperative Postoperativesize Grade Ⅰor Ⅱ Grade Ⅰor Ⅱ GradeⅢ or Ⅳ Grade Ⅴ or ⅥSmall (≤2.0cm) 18 18 0 0Medium (2.1-3.9cm) 46 41 5 0Large(≥4.0cm) 39 27 12 0Total 103 86 17Postoperative ComplicationsThe most frequent postoperative complications were headache, cerebellar edema, and dizziness, which occurred in 11, 3, and 4 patients, respectively; CSF fistula was another complication. Chronic headache was temporary in most cases. The bone flap was replaced or reconstituted in all of our patients, and only focal pain was experienced. A few patients continued to have headaches for several months after the operation, which might be due to compression on or section of the greater occipital nerve. None of the patients had persisting headaches at follow-up. Cerebellar edema was treated with diuretics and cortisone until the symptoms disappeared. CSF fistula was transient and resolved with lumbar spinal fluid drainage and compression on the region of the operative wound. In 1 case the caudal cranial nerves showed some decrease of function manifesting as transient dysphonia and dysphagia.
目的总结儿童髓母细胞瘤(MDB)分层治疗的经验,探索MDB风险分级对预后的影响。方法回顾性分析2011年1月至2019年12月由笔者进行分层治疗的32例MDB患儿的临床资料。根据风险分级标准,将32例MDB患儿分为低危、标危、高危和极高危4组,分析肿瘤风险分级与预后的关系。结果32例MDB患儿平均随访时间为47个月(33~91个月),5年总生存率(OS)和无进展生存率(PFS)分别为57.3%±7.2%和68.7%±8.6%。低危组的OS和PFS明显高于高危组,标危组明显高于极高危组,差异均具有统计学意义(P<0.05)。结论根据MDB的风险分级标准制定分层治疗方案,有利于预测预后和提高MDB治疗的生存率和改善生存质量。
目的探索儿童髓母细胞瘤(MDB)的风险分级和分层治疗对预后的影响。方法回顾性分析自2011年1月至2019年12月由笔者行经小脑延髓裂入路显微手术治疗的32例MDB患儿的临床资料。根据风险分层标准,将MDB分为低危、中危和高危组,分析治疗模式、风险分级与预后的关系。结果本组MDB患儿中肿瘤全切除和近全切除29例,全切除和近全切除率为90.6%,次全切除3例,无手术相关死亡病例,无永久性脑脊液漏。随访时间6~84个月,32例MDB患儿的3年总生存率(OS)为96.9%,5年OS为84.4%。低危组3年、5年OS明显优于高危组,中危组5年OS为91.7%,高危组5年OS仅63.6%。手术后联合化学治疗(ChT)+放射治疗(RT)的综合治疗模式的患儿5年OS为95.5%,单纯手术治疗的效果最差,患儿3年OS仅66.7%(2/3)。结论根据MDB的危险分级制定个体化的治疗方案,有利于提高MDB治疗的生存率和改善生存质量。术后联合ChT+RT对改善MDB预后有重要意义。
目的探讨儿童髓母细胞瘤(MDB)的临床特征和手术入路的选择。方法回顾性分析自2011年1月至2019年12月采用经小脑延髓裂(CMF)入路治疗的32例MDB患儿的临床资料,其中经单侧CMF入路28例,采用双侧CMF入路4例。分析患儿的临床特征及预后。结果发生于<10岁的儿童28例(87.5%),其中<3岁的婴幼儿占21.9%,男性占65.6%。32例患儿全部病程未超过6个月,其中3个月内者占71.9%,主要症状是颅内高压和共济运动障碍。MDB多数位于蚓部或中线部者(90.6%),位于小脑半球者只有9.4%;9.4%的MDB侵袭脑干。肿瘤全切除者29例,全切除率为90.6%;次全切除者3例,1例术后并发小脑性缄默症,1个月后完全恢复。无手术相关死亡病例,无永久性脑脊液漏。结论CMF入路是MDB的最佳手术入路,符合微创原则。掌握MDB的临床特征和CMF入路的原则及技巧,采用精湛的微创神经外科手术技术,有利于提高MDB的疗效。
目的总结经乙状窦后-内听道入路显微外科手术切除内听道脑膜瘤的方法和经验袁探讨在保留面尧听神经功能的基础上实现肿瘤全切除的技巧。方法回顾性分析首都医科大学宣武医院尧中国人民解放军陆军总医院神经外科自1998年1月至2018年12月采用乙状窦后-内听道入路显微外科手术切除尧经病理证实的4例内听道脑膜瘤患者的临床资料和疗效袁分析其手术要点。结果4例患者的肿瘤均获得全切除袁其中1例肿瘤硬膜起源于内听道口的外侧壁(Simpson分级玉级切除)曰3例肿瘤起源于内听道内的硬脑膜袁硬膜附着延伸至内听道腹侧(Simpson分级域级切除)遥3例患者的面神经和耳蜗神经均被解剖分离保护袁另一例患者仅解剖保留面神经遥2例术前听力分级为H2级尧H3级的患者袁术后听力分级分别为H3级和H4级袁另2例术前听力H5级的患者术后听力仍为H5级遥3例患者术后Karnofsky功能状态评分(KPS)为90分袁1例为70分。无围手术期死亡患者。结论乙状窦后-内听道入路是内听道脑膜瘤显微外科切除术的理想入路。手术应以保护面尧听神经为前提袁以广泛切除肿瘤为目的袁包括肿瘤累及的硬脑膜和骨质袁以减少复发的机会袁改良内听道开放的宽度是必要的遥
目的探讨鞍结节脑膜瘤(TSM)的临床和影像学特点,以改善手术疗效。方法回顾性分析自2000年1月至2018年12月由笔者进行显微手术的156例TSM患者的临床资料,包括手术记录、出院记录、随访记录等,测量术前视力、视野及术后改善情况。根据CT和MRI的表现,将其分为巨大、大、中、小四型,分析讨论TSM临床和影像学特征。结果TSM最常见的症状是非对称性视觉障碍,本组术前视力<1.0者,占96.8%,非对称性视力障碍占84.1%;62.2%的肿瘤侵入视神经管内。术前有302只眼视力<1.0,占96.8%,术后218只眼(69.87%)视力改善,64只眼(20.51%)维持术前水平,30只眼(9.62%)恶化。术前73例患者(46.8%)的影像提示视神经管受累,术中探查共有97例视神经管内有肿瘤侵袭(62.2%,97/156)。患者的临床症状持续时间从1个月~5.3年(中位数21个月)。术后视力改善共218只眼(69.87%),64只眼(20.51%)维持术前水平,30只眼(9.62%)恶化。本组患者随访3个月~7.4年,肿瘤的切除程度SimpsonⅠ~Ⅱ145例,其中视力改善101例(69.66%);SimpsonⅢ~Ⅳ11例,其中视力改善8例(72.73%)。结论不对称性视觉功能障碍是TSM最早期,也是最常见的症状。肿瘤往往累及视神经管,这也是TSM术前评估的重点。
Asaminimallyinvasivetechnique,image-guidedtranscorticalsulciortranssylvianapproachishighlyeffectiveforimmediateandcompletehematomaevacuation.
目的探讨听神经瘤显微外科切除的手术策略袁以提高肿瘤的全切除率和面神经功能保护率遥方法解放军总医院第七医学中心神经外科自2008年1月至2016年12月采用显微外科手术治疗听神经瘤患者415例袁术后常规行MRI增强检查判断肿瘤的切除程度及应用Karnofsky行为状态评分(KPS)评估患者的预后遥术后3个月采用House-Brackmann面神经功能分级(H-B)评估患者的面神经功能遥结果KPS评分显示患者预后优399例(96.10%)袁良14例(3.37%)袁差2例(0.48%)曰肿瘤直径越大袁患者预后优者占比越小遥术后MRI增强检查显示肿瘤全切除387例(93.25%)袁次全切除24例(5.78%)袁部分切除4例(0.96%)曰肿瘤直径越大袁全切除者占比越小遥术中面神经解剖保留398例(95.90%)袁未能保留17例(4.09%)袁其中12例患者术中行面神经端-端吻合遥术后3个月H-B分级显示玉~域级334例(80.5%)袁芋~郁级76例(18.3%)袁吁~遇级5例(1.2%)曰肿瘤直径越大袁患者H-B分级玉~域级者占比越小遥无手术相关死亡病例遥结论早期诊断尧早期手术治疗有助于提高听神经瘤显微外科切除的安全性和疗效遥
INSCsreceivingCR2-Crrypre-treatmentincreasedthelevelsofCrryexpressioniniNSCsandiNSC-derivedastrocytesandneuronsandattenuatedcomplement-mediatedinjuryfollowingCHI
Phospholysinephosphohistidineinorganicpyrophosphatephosphatase(LHPP)isanew-foundtumorsuppressorinavarietyoftumors.While,itisstillunknownaboutitsroleinglioma.Inthisstudy,wefoundthatLHPPisabnormallydecreasingorabsentinglioblastoma,andthelowexpressionofLHPPisassociatedwithpoormediansurvivalingliomapatients.FunctionalassayrevealedthatLHPP-overexpressionsignificantlyinhibitedU87MGandU118MGgrowthinvitroandinvivo.Astothemechanism,mass-spectrometricanalysisindicatedthattheLHPPinteractingproteinsweremainlyenrichedinregulationofenergymetabolism,includingCarbonmetabolism,Oxidativephosphorylation,andGlycolysis.SeahorseassayandmetabolitesdetectionconfirmedthatLHPP-overexpressionobviouslyimpededglycolysisandrespirationinU87MGandU118MGcells.Forthefurtherstudy,westernblotassayshowedthattheproteinlevelofPKM2atdimeric,tetrameric,andtotalprotein,werealldecreasedsignificantly,anditsenzymaticactivitywasdecreasedaswell.ChIPandRNAseqintegratedanalysisindicatedthatthedecreasedproteinlevelofPKM2wasindependentofPKM2transcription,andLHPPdidnotreprogramtranscriptionlevelofmetabolicgenome.Co-IPandimmunofluorescenceassaymanifestedthatLHPPinteractedwithPKM2,andthisinteractioninterferedtheproteinstability,theninducedubiquitin-mediateddegradationofPKM2.RescueassayconfirmedthatrestoringtheexpressionofPKM2effectivelyreversedtherestrainedenergymetabolismandtheinhibitedcancercellgrowthcausedbyLHPP-overexpressioninU87MGandU118MGcells.Takingtogether,wedemonstratedthatLHPPimpedestheglycolysisandrespirationduringenergymetabolicprocessviainducingubiquitinmediateddegradationofPKM2,thusinhibitsthegrowthofglioblastoma.