Operative management of trigeminal neuromas: an analysis of a surgical experience with 55 cases

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1 Acta Neurochir (2014) 156: DOI /s CLINICAL ARTICLE - BRAIN TUMORS Operative management of trigeminal neuromas: an analysis of a surgical experience with 55 cases Li-feng Chen & Yang Yang & Xin-guang Yu & Qiu-ping Gui & Bo Bu & Bai-nan Xu & Ding-biao Zhou Received: 7 January 2014 /Accepted: 22 February 2014 /Published online: 15 March 2014 # Springer-Verlag Wien 2014 Abstract Background The trigeminal schwannoma is the second most common intracranial schwannoma. Their proximity to the critical skull base neural and vascular structures increases the complexity of surgical treatment. The aim of this study was to better understand the surgical approaches and the prognosis, as well as to assess the optimum therapeutic schedule. Methods This was a retrospective study of 55 patients with trigeminal schwannomas who visited our department between Jan 2007 and Jan We analyzed the clinical and radiological presentation, tumor characteristics, surgical approaches, the prognosis. Results The patients were 30 women and 25 men of mean age 36 years (range, 6 66 years) who received postoperative neurological and neuroradiological follow-up. The tumor was located in the middle fossa (type A) in 13 cases, in the posterior fossa (type B) in ten cases, in the middle and posterior fossae (type C) in 21 cases, and in the branches of the trigeminal nerve (type D) in 11 cases. The most common symptom was facial hypesthesia or numbness in 36 patients (65 %). Total and nearly total tumor resection was achieved in 51 cases (93 %). Three patients (5 %) had worsening of Li-feng Chen and Yang Yang contributed equally to the manuscript. L.<f. Chen: X.<g. Yu (*) : B. Bu : B.<n. Xu : D.<b. Zhou Department of Neurosurgery, The Chinese PLA General Hospital, the No.28 Fuxing Road, Haidian District, Beijing , China javelins@126.com Y. Yang Department of Geriatric Neurology, The Chinese PLA General Hospital, the No.28 Fuxing Road, Haidian District, Beijing , China Q.<p. Gui Department of pathology, The Chinese PLA General Hospital, the No.28 Fuxing Road, Haidian District, Beijing , China preexisting deficits and there was no perioperative mortality. With an average follow-up period of 35 months, facial hypesthesia persisted in 26 patients (72 %),and improved in ten patients (28 %). Facial pain was relieved in 11 patients (100 %). There has been a recurrence in one case (2 %) and all patients resumed independent and social reintegration. Conclusion This study demonstrates radical surgery with excellent neurological outcomes is the primary treatment of trigeminal schwannomas. Appropriate selection of surgical approach according to tumor types is highly important and necessary. The preoperative facial pain could be relieved, hypesthesia frequently remains or could even be worsened after surgery. Keywords Cavernous sinus. Microsurgery. Skull base approach. Trigeminal schwannoma Introduction Schwannomas of the central nervous system are slowgrowing benign tumors arised from peripheral nerve sheaths. The trigeminal nerve is the second most common intracranial site of occurrence after vestibular nerve origin. The trigeminal schwannoma accounts for 0.07 % to 0.36 % of all intracranial tumors in published series [9, 14, 15, 19, 27]. Their proximity to the critical skull base neural and vascular structures increases the complexity of surgical treatment. Although the significant evolution of microsurgical skull base techniques has led to markedly improved surgical outcomes, it is not easy to obtain satisfactory prognosis for most neurosurgeons. Between Jan 2007 and Jan 2012, we performed microsurgery for 55 patients with the primary trigeminal schwannomas. We reviewed our therapeutic strategies and post-operative follow-ups by retrospective analysis in the present study. The objective was to better understand the

2 1106 Acta Neurochir (2014) 156: clinical and radiological presentation, tumor characteristics, surgical approaches and the prognosis, as well as to assess the optimum therapeutic schedule. Methods and materials Subjects During a 5-year period between Jan 2007 and Jan 2012, 55 consecutive patients with histologically verified trigeminal schwannomas were treated in the Department of Neurosurgery in our hospital by the senior neurosurgeons. The 55 patients included 30 females and 25 males. The mean age was 36 years and ranged from 6 to 66 years. All 55 patients (100 %) had clinical symptoms at presentation. The course of the disease ranged from one month to six years. The clinical information was obtained by hospital charts, clinic notes, and operative reports. Evaluation methods All patients underwent radiological assessment of their lesions by computed tomography (CT) and magnetic resonance imaging (MRI). Tumor size was defined as the greatest contrastenhancing tumor diameter on MRI. The tumors were categorized into the four types according to Day and Fukushima s modified version [6] of the Jefferson classification system. Jefferson categorized the tumors into the following three types [12]: type A, tumor of the gasserian ganglion in the middle cranial fossa; type B, tumor of the roots of the trigeminal nerve in the posterior fossa; and type C, the so-called hourglass tumor occupying both the middle fossa and the posterior fossa. Day and Fukushima [6] added a fourth classification, type D, comprised of schwannomas with an extracranial extension that arises from the branches of the trigeminal nerve. All patients received postoperative follow-up, which ranged from one year to five years (mean 35 months) by neuroimaging and neurological examinations. MR imaging was repeated approximately three months after the operation and annually thereafter to assess for recurrence. Preoperatively, at three months postoperatively, and one year to five years intervals after surgery, the neurological function and neuroimaging evaluations of the patients were recorded. Surgical techniques The selection of surgical approaches for trigeminal schwannomas depended on tumor types according to the location and extension of the tumor (Tables 1, 2 and 3). Each approach was performed conventionally (Fig. 1a, b, c). It was necessary that a continuous external drainage of cerebrospinal fluid by lumbar subarachnoid catheter placement was set up before the extradural operation, and the external ventricular drainage was performed for the patients with hydrocephalus. In the majority of cases, the tumors were moderately vascular, friable in consistency, and had a well-defined arachnoidal plane of dissection from the tumor capsule. Persistent piecemeal tumor resection using careful microsurgical dissection techniques within the tumor was recommended instead of en bloc tumor removal. Tumor removal was usually performed by using blunt dissection with the help of the cavitron aspirator and avoiding coagulation as much as possible. This avoids injury to neighboring neural and vascular structures. Results Preoperative characteristics The duration of the preoperative symptoms ranged from one month to six years, with an average of 36 months. The most common symptom was facial hypesthesia or numbness, followed by headache and dizziness, ataxia, and facial pain. One patient (2 %) had preoperative exophthalmos caused by a peripheral-type tumor originating from the first division of the trigeminal nerve. The preoperative characteristics of the patients are described in detail in Table 2. The tumor was located in the middle fossa (type A) in 13 cases (Fig. 2a, b), the posterior fossa (type B) in ten cases (Fig. 3a, b), the middle and posterior fossa (type C) in 21 cases (Fig. 4a, b, c) and along branches of the trigeminal nerve (type D) in 11 cases (Fig. 5a, b, c).31 (56 %) trigeminal schwannomas were on the right side, and 24 (44 %) were on the left side. The maximum diameter of the tumors ranged from 2.5 to 7.5 cm (mean, 4.6 cm; Figs. 2a, b, 3a, b, 4a, b, c, 5a, b, c). Twenty-four patients (44 %) had tumors between 2.5 and 4 cm. 21 patients (38 %) had tumors between 4 cm and 6 cm and ten patients (18 %) had tumors larger than 6 cm. Thiry-one tumors (56 %) were solid; 23 tumors (42 %) were mixed solid and cystic; and only one tumor (2 %) was cystic (Table 2). Surgical characteristics and results Total tumor resection was achieved in 38 cases (69 %); nearly total tumor resection was performed in 13 cases (24 %); subtotal removal in four patients (7 %), because of difficulties in dissection from cranial nerves, blood vessels, or the brainstem. The senior neuropathologist verified that the histological examinations of all tumors (Fig. 1d) were the benign nature. After surgery, the preoperative neurological status was maintained or improved in 52 patients (95 %). New neurological deficits or worsening of pre-existing deficits occurred in

3 Acta Neurochir (2014) 156: Table 1 Trigeminal schwannoma surgery results and complications reported in the literature Author (Year) Ref Type/NO. of cases Radical removal (%) Mortality (%) Morbidity (%) A B C D Total McCormick (1988) (43 %) 0 % 78 % Pollack (1989) (75 %) 0 % 6 % Dolenc (1994) 7 NA NA NA NA (100 %) 0 % 25 % Konovalov (1996) (77 %) 3 % 87 % Yoshida (1999) (74 %) 0 % 74 % Goel (2003) (70 %) 3 % 7 % Pamir (2007) (94 %) 0 % 28 % Wanibuchi (2012) (82 %) 0 % 9 % Chen (2013, present study) (95 %) 0 % 5 % Table 2 Perioperative characteristics in 55 patients with trigeminal schwannomas Characteristics/NO. of cases n=55 Postoperative improvement Immediate Medium term a Demographics Mean age 36 years Range 6 66 years Ratio (M:F) 1:1.2 Tumor features Mean size 4.6 cm Range cm Tumor type A 13 (24 %) B 10 (18 %) C 21 (38 %) D 11 (20 %) Tumor texture Solid 31 (56 %) Mixed solid and cystic 23 (42 %) Cystic 1 (2 %) Majoy presenting complaints Facial hypesthesia 36 (65 %) 3 (8 %) 10 (28 %) Headache and dizziness 27 (49 %) 16 (59 %) 27 (100 %) Ataxia 12 (22 %) 8 (67 %) 12 (100 %) Facial pain 11 (20 %) 11 (100 %) 11 (100 %) Diplopia 10 (18 %). 5 (50 %) 7 (70 %) Atrophy of temporal muscle 8 (15 %) 0 2 (25 %) Decreasedhearing 5(9%) 0 1(20%) Decreased visual acuity 3 (5 %) 1 (33 %) 2 (67 %) Exophthalmos 1 (2 %) 1 (50 %) 1 (100 %) Hydrocephalus 5 (9 %) 5 (100 %) 5 (100 %) a Six months after operation in the series three patients (5 %). Of the three patients, preoperative facial hypesthesia worsened in one patient; Diplopia worsened in one patient; New ptosis was observed in one patient. There was no perioperative mortality. Three patients had postoperative complications. The most common postoperative complication was cerebrospinal fluid leak (in two patients). They were successfully treated with lumbar drainage for 5 7 days. One patient experienced right temporal lobe hematoma, which was treated with surgical debulking. The extent of resection and immediate postoperative results for all patients are presented in Tables 4 and 5. Postoperative course In the mean 35 months of follow-up, all 55 patients resumed independent and social reintegration (Table 5). Facial pain relieved in all patients (100 %). Facial hypesthesia persisted in 26 patients (72 %), and improved in ten patients (28 %). The muscle atrophy persisted in six patients, and improved in two patients. The headache, dizziness and ataxia were relieved in all patients (100 %). Diplopia improved for seven of ten patients with preoperative diplopia, and persisted in three patients. One patient with new ptosis recovered after six months. Visual acuity improved for two patients. Hearing subjectively improved in one patient. Symptomatic improvement in patients with trigeminal schwannomas is presented in Table 2. No patient who underwent total tumor resection experienced tumor recurrence (Figs. 2c, d, 3c, d, 4d, e, f, 5d, e, f). Of the one type C patient operated via the zygomatic temporopolar extra-intradural approach who underwent subtotal removal, tumor regrowth was also observed. There were no symptoms, but the tumor was detected via MRI. Stereotactic radiotherapy was suggested to control tumor growth for her.

4 1108 Acta Neurochir (2014) 156: Table 3 Operative approach in 55 patients with trigeminal schwannomas Operative approach/type A (n=13) B (n=10) C (n=21) D (n=11) Transzygomatic extradural temporopolar Lateral basal extradural subtemporal Suboccipital retromastoid Transzygomatic extra-intradural temporopolar Two-staged surgery a Transzygomatic anterior infratemporal fossa Cranioorbital extradural a combined extradural temporopolar and retrosigmoid approach Discussion Clinical presentation Schwannomas are benign tumors of peripheral nerve sheaths that arise distal to the oligodendroglial-schwann myelination junction. Acoustic schwannomas are the most common kind of these tumors in the literature. Schwannomas of the other cranial nerves are rare [9, 14, 15, 19, 27]. The trigeminal nerve is the second most common intracranial site of occurrence after vestibular nerve origin. Although the trigeminal schwannoma was first described by Dixon in 1846, it is quite rare [1]. It accounts for 0.8 % to 8 % of all intracranial schwannomas [9, 14, 15, 19, 27]. Trigeminal schwannomas occur most frequently in middle-aged patients, and no sex preponderance is seen [9, 20]. In our series, there was no significant sex variation with the male/female ratio being 1:1.2, and the patients ranged from 6 to 66 years of age (mean, 36 years). Neurofibromatosis was less commonly associated with trigeminal neuromas [1]. There were no cases of bilateral trigeminal schwannomas in our series, which may be associated with neurofibromatosis [1]. Trigeminal schwannomas can arise anywhere between the root and the distal extracranial branches of the trigeminal nerve [16]. Their symptoms and signs depend on tumor location and extent of tumor growth. In our series, the most common presenting symptom was facial hypesthesia, followed by headache, dizziness and ataxia. Similar presenting symptoms had been reported in other studies [9, 16, 25]. Since schwannomas originate from peripheral nerve sheaths, the uninvolved fibers of the nerve are theoretically compressed, and schwannomas should be resected with Fig. 1 Intraoperative photographs of the trigeminal schwannoma removal showing: a Epidural-interdural exposure of a type A trigeminal schwannoma via the right transzygomatic extradural temporopolar; b After removal of the right zygomatic arch and sphenoid ridge (thick arrow), the dura mater (thin arrow) of right temporal lobe were exposed; c The dura mater of right temporal lobe was elevated from the middle skull base. Interdural dissection was achieved by peeling back the dura covering the V2 and V3 nerves from the foramina rotundum and ovale, respectively. The tumor (Tu.), V2 (think arrow) and V3 (thin arrow) were visible; d The specimen with complete tumor removal

5 Acta Neurochir (2014) 156: Fig. 2 Preoperative a axial and b coronary T1-weighted contrastenhanced MRI showing a right type A trigeminal schwannoma. The patient was operated on without any complication. Postoperative c axial and d coronary T1-weighted contrastenhanced MRI three years after surgery showing complete tumor removal preservation of the normal uninvolved fibers. Actually, similar to the facial nerve observed in acoustic neuromas, the normal trigeminal nerve fibers are usually tightly adherent to the tumor. Preservation of trigeminal nerve function in most patients is difficult, even with a meticulous surgical technique. The significant evolution of microsurgical skull base techniques had led to markedly improved surgical outcomes, and preoperative hypesthesia improved postoperatively in some cases of recent reports [9, 16, 25]. However, the symptoms persisted or worsened in more cases. Goel et al. [9] reported that the preoperative trigeminal sensory deficit improved in 40 % of the patients but worsened to anesthesia in 27 %. Wanibuchi [25] reported that the preoperative trigeminal sensory deficit improved in 16 %, persisted in 73 %, and worsened in 12 %. New hypesthesia was observed in 22 % of patients. In our series, facial hypesthesia persisted in 26 patients (72 %), improved in 10 patients (28 %), facial pain relieved in 11 patients (100 %), and the muscle atrophy improved in two patients at six months after surgery. The second most common symptoms were headache, dizziness and ataxia. These symptoms related to increased intracranial pressure and cerebellar symptoms, which were attributed to large tumor size. In our series, the mean maximum diameter of the tumors was 4.6 cm, and 56 % of the patients had tumors larger than 4 cm. All patients with headache, dizziness and ataxia were relieved after the tumors were resected. The symptoms of involvement of adjacent cranial nerves in the cavernous sinus have been frequently reported in the literature [9, 16, 25]. Wanibuchi [25] reported 20 % of their patients complained of diplopia, 86 % of these patients had a deficit of the abducens nerve, and 14 % had a deficit of the oculomotor nerve. Al-Mefty et al. [1] reported that 52% of their patients complained of diplopia, and 40 % of these patients had a deficit of the sixth nerve. Among the 18 % of patients complaining of diplopia in our series, diplopia resulted from palsy of the abducens nerve in eight of these ten patients. This symptom improved in six of these eight patients postoperatively. In two other patients, diplopia caused by palsy of the oculomotor nerve improved in one patient, and persisted in one patient postoperatively.

6 1110 Acta Neurochir (2014) 156: Fig. 3 Preoperative a axial and b sagittal T1-weighted contrastenhanced MRI showing a right type B trigeminal schwannoma. The patient was operated on with retromastoid approach. Postoperative c axial and d sagittal T1-weighted contrastenhanced MRI three months after surgery showing complete tumor removal Radiological features Preoperative radiological evaluation could provide the precise location of the trigeminal schwannoma, its relationship with neighboring neural and vascular structures, and establish the type of trigeminal schwannomas. It helps to guide the surgical strategy. In our series, tumors in the middle fossa and dumbbell-shaped tumors occupying both the middle fossa and the posterior fossa made up 62 % of patients. Similar with our data, Goel [9] reported tumors occupying the middle fossa and the posterior fossa made up 81 % of patients. Wanibuchi [25] reported tumors occupying the middle fossa and the posterior fossa accounted for 66 % of patients. Goel [9] reported that cystic or necrotic changes within the tumor mass were observed in 54 % of patients. In our series, 42 % were mixed solid and cystic; and only 2 % were cystic. This is similar with previous reports [9, 16]. The invasion of the venous spaces of the cavernous sinus and encasement of the cavernous sinus portion of the internal carotid artery were not encountered in any case of our series. We agreed that the trigeminal schwannoma usually displaced the neighboring neural and vascular structures, which was characteristic and had important diagnostic value [9, 13]. Computed tomographic scans could show enlargement of superior orbital fissure, the foramen ovale or foramen rotundum, as well as erosion of the middle fossa and the petrous apex. These findings were also a diagnostic characteristic. Trigeminal schwannomas were usually moderately vascular and friable in consistency [9]. Unlike Pamir s report [16], we found preoperative cerebral angiography was not necessary. We did not routinely perform preoperative angiography. Surgical management Since trigeminal schwannomas have a very close relationship with the deep critical skull base neural and vascular structures, and until the introduction of the operating microscope, the early surgical morbidity and mortality rates associated with resection of trigeminal schwannomas were significant. The literature [23] demonstrated a 1-year mortality rate of 41 % for the 39 operative cases of trigeminal schwannomas up to Arseni and Camenita [2] noted 25 % postoperative mortality for all cases published before Over the course of the next 30 years [9, 13, 15, 16, 19, 25, 28], advances in neuroanatomy, neuroimaging, and microsurgical technique have brought out better results (Table 1). The surgical morbidity and mortality rate associated with resection of trigeminal schwannomas have been improved. Most recent reports demonstrated higher rates of radical surgery, acceptable surgical

7 Acta Neurochir (2014) 156: Fig. 4 Preoperative a axial, b coronary and c sagittal T1-weighted contrast-enhanced MRI showing a large left type C trigeminal schwannoma. The patient was operated on with the transzygomatic extra-intradural temporopolar approach. Postoperative d axial, e coronary and f sagittal T1-weighted contrast-enhanced MRI two years after surgery showing complete tumor removal morbidity rates, and long-term recurrence-free intervals. In the series of Wanibuchi [25] in 2013, total or near-total removal was performed in 82 % and no patients died. In our study, total or near-total removal was achieved in 95 % patients for 55 cases. All patients demonstrated improvements in their functional ability, and resumed independence. One patient had a recurrence in the mean 35 months of follow-up. Radical resection leads to tumor cure and the recurrence rate for cases with partial resection is relatively higher for trigeminal schwannomas, compared with acoustic schwannomas [8]. Many reports [9, 16, 25] haveemphasized the need for complete surgical excision. Total tumor removal with minimal morbidity is the primary goal for trigeminal schwannomas. The major impediment to complete resection is inadequate exposure and tumor adherence to vital skull base neural or vascular structures [7, 9, 16, 19]. Adequate exposure is dictated by the selection of the appropriate surgical approach according to the type of tumor. In the past 30 years, the knowledge of the pertinent anatomy that the middle fossa component and the extracranial component of trigeminal neurinomas are located in the interdural compartment, whereas the posterior fossa component of the tumor is located within the subarachnoid compartment and the extradural strategy, are the most important evolutions [11, 16]. Type A trigeminal schwannomas are located in the interdural space and enveloped by the inner membrane of the cavernous sinus [16]. Subtemporal, fronto-temporal intradural and fronto-temporal epidural approaches have ever been described for removing these tumors [8, 17, 20]. With the intradural approach, the tumor was exposed after the dura was opened. It required significant brain retraction and usually demanded the sacrifice of bridging veins at the temporal pole [21]. The transzygomatic extradural temporopolar approach was described by Dolenc [7] in The transzygomatic extradural temporopolar approach has the advantage of more direct access to the region with less brain retraction required. If more exposure is needed, the brain tissue can be retracted while being protected by overlying dura, which helps preserve venous structures and brain tissue. Yoshida and Kawase [28] began to use a lateral basal subtemporal approach for Type A trigeminal schwannomas in They found that direct access from the lateral direction by performing temporal

8 1112 Acta Neurochir (2014) 156: Fig. 5 Preoperative a axial, b coronary and c sagittal T1-weighted contrast-enhanced MRI showing a large type D trigeminal schwannoma. The patient was operated on via the transzygomatic anterior infratemporal fossa approach without any complication. Postoperative d axial, e coronary and f sagittal T1-weighted contrast-enhanced MRI one year after surgery showing complete tumor removal craniotomy provided the shortest and shallowest corridor to the Meckel cave and avoided injury to the abducens nerve. We used the transzygomatic extradural temporopolar approach for 12 Type A trigeminal schwannomas and achieved excellent surgical and clinical results. We found that this approach provided a low and wide exposure and avoided direct brain retraction. It allowed for easy dissection of the tumor from surrounding structures. There was low morbidity of cranial nerve injury and no complications related to brain retraction. It was as easy to expose large tumors as it was to expose small tumors with this approach. With the lateral basal subtemporal approach, it was difficult to obtain a pericavernous wide exposure. This approach provided a limited view of the front of the cavernous sinus, especially for large tumors, and we used the lateral basal subtemporal approach for only one small Type A trigeminal schwannoma. Although the literature discussed the use of the transpetrosal transtentorial approach for Type B trigeminal schwannomas [9, 27, 26], we found the classical suboccipital retromastoid exposure was satisfactory for Type B trigeminal schwannomas. We used the retromastoid approach for all 10 Type B patients. Total excision was achieved in all of them, and morbidity is low. With this approach, tumor debulking and dissection could be done as recommended for resecting petroclival meningioma, the main part of which is located in the posterior fossa [5]. For type C tumors, an extended transzygomatic extradural temporopolar approach or a combined transzygomatic extradural temporopolar and retrosigmoid approach were selected. Type C trigeminal schwannomas occupied both the middle fossa and the posterior fossa. It was well known that resecting the type C tumor is the most challenging in Table 4 Extent of resection in 55 patients with trigeminal schwannomas Extent of resection/type A (n=13) B (n=10) C (n=21) D (n=11) Total Total (69 %) Nearly total (24 %) Subtotal (7 %)

9 Acta Neurochir (2014) 156: Table 5 Operative outcome in 55 patients with trigeminal schwannomas Complications/NO. of cases n=55 Immediate a Facial hypesthesia 1 0 Diplopia 1 0 Ptosis 1 0 Cerebrospinal fluid leak 2 0 Hematoma 1 0 Postoperative deaths 0 0 a new neurological deficits or worsening of pre-existing deficits b Six months after operation in the series Medium term b trigeminal schwannomas surgery. Prior studyies [3, 15, 22, 27] reported removing these tumors via a subtemporal transtentorial route, a combination of the retrosigmoid and subtemporal approach and a transpetrosal transtentorial approach or an orbitozygomatic infratemporal approach. Goel [8 10] found the posterior fossa component of the tumor can frequently be interdural in location, being covered by dura, and the posterior fossa component of the tumor can be resected through a middle fossa exposure or even infratemporal fossa exposure. Of the 21 cases of Type C trigeminal schwannomas in our series, 18 were performed via a transzygomatic extra-intradural temporopolar approach, and two were performed via a transzygomatic extradural temporopolar approach. Another patient had the dumbbelltype tumors with a large posterior fossa extension that could not be resected through the middle cranial fossa and the expanded Meckel cave. The patient underwent a combined extradural temporopolar and retrosigmoid approach. Unlike meningiomas located at the petrosa clivus area, the posterior fossa component of trigeminal schwannomas usually does not attach to any posterior fossa structure. The petrous bone absorption due to tumor compression usually enlarges the outlets of the trigemial nerve. Most of the cavernous root dumbbell-type tumors with a posterior fossa extension can be resected via the middle cranial fossa [9]. Although many authors do not recommend a two-stage tumor resection, a single middle fossa surgery was not a good surgical option in some tumors with a large and lower posterior fossa extension. Resection of the residual lesion in the posterior fossa after a middle fossa surgery by a retrosigmoid operation can be a rather simple surgical procedure. Type D trigeminal schwannomas can originate from the first division (V1) of the trigeminal nerve, or the second (V2) or third (V3) division of the trigeminal nerve. The former erode the superior orbital fissure and extend into the orbit. The latter erode the base of the middle fossa, and extend to the infratemporal fossa via the foramen ovale or foramen rotundum. These tumors can be accessed via an entirely extradural approach [11, 22]. Our series featured 11 type D tumors, and we successfully excised the tumors via a cranioorbital extradural approach or transzygomatic extradural approach via the anterior infratemporal fossa. Treatment alternatives Stereotactic radiotherapy is an alternative primary or adjuvant strategy that controlls tumor growth for trigeminal schwannomas [4, 9, 16 18, 24, 25]. It has been proposed as a treatment strategy for trigeminal schwannomas in some reports [4, 17, 18, 24]. The experiences with a large sample from a randomized clinical trial are limited. Radiation toxicity of the brain should not be ignored [4, 17, 18, 24]. In our experience, radical surgical resection with safe and excellent neurological outcomes and long-term tumor control should be the first option for the patients. However, the goal for managing recurrent and residual trigeminal schwannomas should be to control tumor growth, and if a tumor cannot be resected completely and the residual or recurrent tumor is less than 3 cm in size, stereotactic radiotherapy is another useful option. So, the patients who have asymptomatic primary small tumors located in the cavernous sinus, residual or recurrent tumor smaller than 3 cm diameter could be suggested as the option of stereotactic radiotherapy. Conclusion This study demonstrates radical surgery with excellent neurological outcomes is the primary treatment for trigeminal schwannomas. Appropriate selection of the surgical approach according to tumor types is highly important and necessary. The preoperative facial pain could be relieved, but hypesthesia frequently remains or is even worsened after surgery. Conflict of interest None. Financial support information This work was supported by grants from the Technological innovation fund of the PLA General Hospital (no. 12KMM040). References 1. Al-Mefty O, Ayoubi S, Gaber E (2002) Trigeminal schwannomas: removal of dumbbell shaped tumors through the expanded Meckel cave and outcomes of cranial nerve function. J Neurosurg 96: Arseni C, Camenită A (1980) Unusual clinical aspects in the development of acoustic nerve neurinoma. Rev Med Interna Neurol Psihiatr Neurochir Dermatovenerol Neurol Psihiatr Neurochir 25:

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