Preauricular retromandibular trans tympanic plate and styloid process keyhole approach to parapharyngeal lesions: a laboratory study.

BACKGROUND: The surgical removal of the infratemporal parapharyngeal lesions (IPL) is challenging due to its anatomical complexity. Previous surgical approaches have often been too invasive and necessitated sacrifice of normal function and anatomical structures, particularly in the retromandibular nerve region. Therefore, we sought to identify an approach corridor to this area that requires less sacrifice and report an innovative approach through a retromandibular fossa route to the IPL. METHODS: Five cadaveric specimens were dissected bilaterally with a trans-tympanic plate and styloid process approach. These specimens were investigated microanatomically and morphometrically to examine the extent of the approach in the parapharyngeal space. The clinical application of this approach was compared to previous approaches to the IPL used in our clinical series of 20 cases. RESULTS: Using this novel approach, the inferior alveolar nerve was identified in all specimens, while the chorda tympani and lingual nerve were identified in 6 (60%) and 4 (40%) dissections, respectively. In all specimens, the petrous portion of the internal carotid artery and the exit of the lower cranial nerve were identified. The average length of the exposed lower cranial nerves was 16.6 ± 3.8 mm (range: 11-25 mm). CONCLUSIONS: The described approach is feasible for accessing the IPL at the retromandibular nerve and is less invasive than conventionally used approaches.

Wedge-technique for transposition of the vertebral artery in microvascular decompression for hemifacial spasm: technical nuances and surgical outcomes.

BACKGROUND: Transposition of the vertebral artery (VA) for microvascular decompression for hemifacial spasm (HFS) is often challenging. Various procedures have been proposed to transpose the immobile tortuous VA that cannot be decompressed satisfactorily in the usual manner. METHODS: A Teflon piece that is cut into a wedge shape was used for transposition of the VA as an offending artery in HFS. One or more wedge-shaped Teflon pieces were simply inserted into a small space between the VA and the brainstem or cerebellar hemisphere without any contact with the entry into the root exit zone (REZ) of the facial nerve. A minimal space can be created by slight mobilization of the VA through rostral or caudal, or in between to the lower cranial nerves (LCNs). In cases of a hypertrophic VA that is hard to mobilize, two or more rigid wedge-shaped Teflon pieces that are coated by fibrin glue can be applied to obtain adequate mobilization of the VA. Moreover, a much harder Teflon bar, which is bent into a V shape, can be used in cases of an immobile VA. Once the VA is transposed to an appropriate position, the Teflon, VA, and contacted surface of the brainstem are fixed together by drops of fibrin glue. RESULTS: The offending arteries were VA-posterior inferior cerebellar artery (PICA) in eight cases, VA in four cases, PICA in four cases, VA-anterior inferior cerebellar artery (AICA) in one case, and AICA in one case. Eighteen cases of HFS were successfully treated using the "Wedge technique." Symptoms disappeared within 2 weeks in all patients. Transient facial nerve palsy developed in one case, and transient hoarseness developed in one case. CONCLUSIONS: The wedge technique is a simple straight-line maneuver that facilitates sufficient transposition of the VA without any related complications. This technique is also useful for other large offending vessels, such as the anterior or posterior inferior cerebellar arteries, which are hard to mobilize due to the torque of the vessels.

Single-stage total resection of giant dumbbell-shaped hypoglossal schwannoma: a case report.

Extensive large dumbbell-shaped hypoglossal schwannoma is extremely rare, and total resection is nearly impossible. We present a case of a 61-year-old male with a giant-size hypoglossal schwannoma with moderate tongue atrophy. The tumor extended from the enlarged hypoglossal canal to the brainstem intradurally and the high cervical region extradurally. Through the extreme lateral infrajugular transcondylar (ELITE) skull base approach, the tumor was totally removed in a single-stage operation. Single-stage total resection is feasible by an experienced skull base team utilizing transcondylar skull base techniques and high cervical dissection.

Middle infratemporal fossa less invasive approach for radical resection of parapharyngeal tumors: surgical microanatomy and clinical application.

Surgery of the infratemporal fossa (ITF) and parapharyngeal area presents a formidable challenge to the surgeon due to its anatomical complexity and limited access. Conventional surgical approaches to these regions were often too invasive and necessitate sacrifice of normal function and anatomy. To describe a less invasive transcranial extradural approach to ITF parapharyngeal lesions and to determine its advantages, 17 patients with ITF parapharyngeal neoplasms who underwent tumor resection via this approach were enrolled in the study. All lesions located in the ITF precarotid parapharyngeal space were resected through a small operative corridor between the trigeminal nerve third branch (V3) and the temporomandibular joint (TMJ). Surgical outcomes and postoperative complications were evaluated. Pathological diagnosis included schwannoma in eight cases, paraganglioma in two cases, gangliocytoma in two cases, carcinosarcoma in one case, giant cell tumor in one case, pleomorphic adenoma in one case, chondroblastoma in one case, and juvenile angiofibroma in one case. Gross total resection was achieved in 12 cases, near-total and subtotal resection were in 3 and 2 cases, respectively. The most common postoperative complication was dysphagia. Surgical exposure can be customized from minimal (drilling of retrotrigeminal area) to maximal (full skeletonization of V3, removal of all structures lying lateral to the petrous segment of internal carotid artery) according to tumor size and location. Since the space between the V3 and TMJ is the main corridor of this approach, the key maneuver is the anterior translocation of V3 to obtain an acceptable surgical field.

Surgical management of vestibular schwannomas after failed radiation treatment.

Increasing numbers of patients with vestibular schwannoma (VS) have been treated with focused-beam stereotactic radiation treatment (SRT) including Gamma knife, CyberKnife, X-knife, Novalis, or proton beam therapy. The purpose of this study was to document the incidence of tumor regrowth or symptoms that worsened or first developed following SRT and to discuss surgical strategies for patients who have failed SRT for VS. A consecutive series of 39 patients with SRT failed VS were surgically treated. Clinical symptoms, tumor regrowth at follow-up, intraoperative findings, and surgical outcome were evaluated. There were 15 males and 24 females with a mean age of 51.8 years. Thirty-six patients (92.3%) demonstrated steady tumor growth after SRT. Two (5.1%) patients with slight increase of the mass underwent surgical resection because of development of unbearable facial pain. Symptoms that worsened or newly developed following SRT in this series were deafness (41%), dizziness (35.9%), facial numbness (25.6%), tinnitus (20.5%), facial nerve palsy (7.7%), and facial pain (7.7%). Intraoperative findings demonstrated fibrous changes of the tumor mass, cyst formation, and brownish-yellow or purple discoloration of the tumor capsule. Severe adhesions between the tumor capsule and cranial nerves, vessels, and the brainstem were observed in 69.2%. Additionally, the facial nerve was more fragile and irritable in all cases. Gross total resection (GTR) was achieved in 33.3% of patients, near-total resection (NTR) in 35.9%, and subtotal resection (STR) in 30.8% of patients. New facial nerve palsy was seen in seven patients (19.4%) postoperatively. Our findings suggest that patients with VS who fail SRT with either tumor progression or worsening of clinical symptoms will have an increased rate of adhesions to the neurovascular structures and may have radiation-influenced neuromalacia. Salvage surgery of radiation-failed tumors is more difficult and will have a higher risk of postoperative complications. Radical total resection may not be feasible, and conservative modality of subtotal resection needs to be considered to avoid new neurologic deficits.

Less invasive transjugular approach with Fallopian bridge technique for facial nerve protection and hearing preservation in surgery of glomus jugulare tumors.

For the past three decades, surgery of glomus jugulare tumors (GJTs) has been characterized by extensive combined head and neck, neuro-otologic, and neurosurgical approaches. In recent years, the authors have modified the operative technique to a less invasive approach for preservation of cranial nerves while achieving satisfactory tumor resection. We evaluated and compared the clinical outcomes of our current less invasive approach with our previous more extensive procedures. The clinical records of 39 cases of GJT surgically treated between 1992 and 2011 were retrospectively reviewed. The less invasive transjugular approach with Fallopian bridge technique (LI-TJ) was used for the most recent five cases. The combined transmastoid-transjugular and high cervical (TM-HC) approach was performed in 30 cases, while four cases were treated with a transmastoid-transsigmoid approach with facial nerve translocation. Operative technique, extent of tumor resection, operating time, hospital stay, and morbidity were examined through the operative records, and a comparison was made between the LI-TJ cases and the more invasive cases. No facial nerve palsy was seen in the LI-TJ group while the TM-HC group demonstrated six cases (17.6%) of facial palsy (House-Brackmann facial nerve function grading scale grade II and III). The complication rate was 0 % in the LI-TJ group and 16.7% in the more invasive group. The mean operative time and hospital stay were shorter in the LI-TJ group (6.4 h and 4.3 days, respectively) compared with the more invasive group (10.7 h and 8.0 days, respectively). The LI-TJ approach with Fallopian bridge technique provided adequate tumor resection with cranial preservation and definitive advantage over the more extensive approach.

The history of the combined supra- and infratentorial approach to the petroclival region.

Lesions of the ventrolateral brainstem, clivus, and cerebellopontine angle pose significant challenges for surgeons, and the rate of morbidity and mortality from classic neurosurgical approaches has proven to be unacceptably high. Early attempts to expose this region consisted primarily of an extended suboccipital craniectomy, with opening of the tentorium and ligation of the sigmoid sinus for additional exposure. During the 1960s, technological innovations including the surgical microscope and the pneumatic drill allowed surgeons to gain additional exposure by removing more bone from the base of the skull. This let surgeons define combined infra- and supratentorial approaches, which rely less on brain retraction to resect these difficult tumors successfully. These approaches rely on a combined posterior mastoid approach with an anterior petrosectomy. The evolution of this approach is discussed in this paper.

Gross Total Resection of a Recurrent Cavernous Sinus Meningioma through a Combined Transzygomatic Transcavernous and Extended Middle Fossa Approach with Cavernous Carotid Denudation.

Objective The aim of this study is to describe surgical management of invasive cavernous sinus meningioma with a combination of skull base approaches. Design This study is an operative video. Results Resection of the recurrent skull base meningioma is still challenging, especially if the tumor involves or encases the carotid artery. In this video, we describe our experience with the successful treatment of a recurrent skull base meningioma, which involved the entire cavernous sinus and the internal carotid artery. A 53-year-old male presented with a 1-year history of progressing right-side complete oculomotor palsy and facial dysesthesia. The patient had previously undergone craniotomy for the right-side petroclival cavernous meningioma ( Fig. 1A and B ). Total 8 years after the first surgery, the remaining portion of the cavernous sinus grew up and extended into the posterior fossa ( Fig. 1C ). Then the second surgery was performed to resect only the posterior fossa component ( Fig. 1D ). However, the follow-up magnetic resonance imaging revealed an aggressive tumor regrowth in 2 years. The tumor occupied the right middle fossa with an extension to the posterior fossa and infratemporal fossa ( Fig. 1E and F ). We scheduled to perform gross total resection of the tumor through a combined transzygomatic transcavernous and extended middle fossa approach with preparation for vessel reconstruction. Mild adhesion between the tumor and the cavernous carotid artery facilitated complete resection of the intracavernous component of the tumor ( Fig. 2A-C ). Conclusion A combination of skull base approaches provides multidirectional operative corridors and wide exposure of the skull base lesions. The link to the video can be found at https://youtu.be/DB_WXFeyBvo .

Gross Total Resection of a Recurrent in-and-around Cavernous Sinus Meningioma through a Combined Transcavernous Anterior and Middle Infratemporal Fossa Approach with Extracranial-Intracranial Bypass.

Objectives The study aims to describe surgical management of an invasive cavernous sinus meningioma with a combination of several skull base approaches and bypass surgery. Design This study is an operative video. Results Resection of the recurrent skull base meningioma is still challenging, especially if the tumor involves or encases the carotid artery. Cerebral bypass surgery is an essential adjunct in the armamentarium of skull base surgery when vessel reconstruction is required. In this paper, we describe our experience of successful treatment of an invasive recurrent skull base meningioma, which involved the entire cavernous sinus and the internal carotid artery. A 46-year-old woman presented with a 2-year history of gradually worsening left-sided exophthalmos and visual impairment. The patient had previously undergone two craniotomies for resection of the left-sided spheno-orbital meningioma. Pathological diagnosis was chordoid meningioma, which is classified as an intermediate-grade meningioma. The second surgery had been performed for a rapid tumor regrowth 6 months after the first surgery. The patient lost her left-side vision after the second surgery. Aggressive tumor regrowth was confirmed with extension into the left orbit, infratemporal fossa, and cavernous sinus with engulfment of the carotid artery. A balloon occlusion test revealed intolerance of the left internal carotid artery occlusion. Considering the patient's age, tumor behavior, and intolerance of the carotid artery of the lesion side, we scheduled gross total resection of the tumor with vessel reconstruction. Conclusion Although cerebral bypass surgery is a technically challenging procedure, it plays an important role in the surgical management of the complex vessel-engulfing tumor. The link to the video can be found at https://youtu.be/GCmpxK3hW18 .

Micropatties Are Indispensable Instruments for Successful Microneurosurgery: Technical Note.

BACKGROUND: Neurosurgical micropatties (also known as sponges or cottonoids) have been used in microsurgical procedures to protect the brain surface and aspirate cerebrospinal fluid and blood. We sought to describe unique applications of micropatties in neurosurgical interventions. METHODS: Various sizes of micropatties have been used in neurosurgical interventions including tumor, vascular, and skull base surgeries to enhance safe surgical procedures and clear the operative field. Their roles are divided into 3 types: tissue protectors, instrument assistants, and instruments in the microsurgical procedures. RESULTS: Appropriate use of micropatties provides a well-visualized operative field, easy identification of bleeding spots, effective tumor elevation from the cleavage layer, and precise procedures around critical structures. CONCLUSIONS: To achieve safe and successful neurovascular protective surgery, micropatties play an important role in any type of microsurgical procedure in their various applications.

Basal Cistern Effacement and Pseudo-Subarachnoid Hemorrhage on Computed Tomography Images of Chronic Subdural Hematoma.

OBJECTIVE: Computed tomography images of patients with chronic subdural hematoma (CSDH) sometimes show obliteration of the basal cistern with high density in an obliterated Sylvian cistern, termed pseudo-subarachnoid hemorrhage (SAH). The present study aimed to clarify the characteristics and outcomes of these conditions. METHODS: We retrospectively investigated 669 consecutive patients who were surgically treated for CSDH between January 2006 and May 2019. RESULTS: Basal cistern effacement and pseudo-SAH were found in 24 (3.6%) and 11 (1.6%) patients, respectively. Predictors of basal cistern effacement in patients with CSDH were younger age, cerebrospinal fluid leak, and bilateral CSDH (P < 0.05). In patients with basal and Sylvian cistern effacement, the significantly different main features to differentiate patients with and without pseudo-SAH were younger age, cerebrospinal fluid leak, and thick small hematomas on computed tomography slices of the Sylvian cistern (P < 0.05). Magnetic resonance imaging showed that high-density areas in the Sylvian cistern of pseudo-SAH on precontrast computed tomography images corresponded to the M1 segment of the middle cerebral artery. The outcomes of patients with basal cistern effacement and of patients with pseudo-SAH did not differ from other patients with CSDH, although rates of surgical complications were significantly higher among patients with basal cistern effacement. CONCLUSIONS: Although the outcomes of patients with basal cistern effacement and pseudo-SAH were similar to outcomes of other patients with CSDH, problematic postsurgical complications and cerebrospinal fluid leaks were more likely to arise in such patients.

Recurrent Trigeminal Neuralgia Caused by a Subsequently Developed Offending Artery Within a Short Period.

BACKGROUND: Recurrent trigeminal neuralgia after successful microvascular decompression is not rare. CASE DESCRIPTION: A 72-year-old woman who presented with typical right trigeminal neuralgia had been successfully treated by microvascular decompression with transposition of the superior cerebellar artery. However, she complained of trigeminal neuralgia on the ipsilateral side 14 months after the microvascular decompression. Redo microvascular decompression showed that the anterior inferior cerebellar artery, which had not been detected at the initial surgery, compressed the right trigeminal nerve. CONCLUSIONS: This case is an unusual type of recurrent trigeminal neuralgia because of a subsequently developed offending vessel within a short period.

The combination of warfarin use and the spot sign leads to detrimental outcomes in patients with intracerebral hematomas.

OBJECTIVES: While warfarin use and the presence of the spot sign on computed tomography angiography are associated with a high frequency of hematoma enlargement and high mortality among patients with intracerebral hematomas (ICHs), the effects of various combinations of warfarin use and/or the spot sign have never been clarified. The combinations of both or either of warfarin use and/or the spot sign were used to investigate their relationships with hematoma enlargement and mortality before the introduction of prothrombin complex concentrate (PCC) treatment. PATIENTS AND METHODS: Consecutive patients with ICHs admitted within 6 h of onset from 2009 to 2017 were investigated. RESULTS: Of 703 eligible patients, the combinations of warfarin use and spot sign-present and of warfarin use and spot sign-absent were seen in 23 (3.3%) and 35 patients (5.0%), respectively. The combination of warfarin use and spot sign-present was a predictor of hematoma enlargement (p < 0.05). In regard to mortality (13.5% for all patients), mortality with the combination of warfarin use and spot sign-present was 52.2%, which was significantly higher than in the 3 other groups. Multivariate analysis showed that the combination of warfarin use and spot sign-present was a significant predictor of mortality (p < 0.05). CONCLUSION: Warfarin users with ICHs showing spot signs, who accounted for approximately 40% of ICH patients with warfarin use, showed a high frequency of hematoma enlargement and high mortality. This group was regarded as high-risk patients and should be considered candidates for prompt administration of PCC.

Prehospital information and spot sign are complementary predictors of post-admission outcomes of intracerebral hematoma.

Prehospital information of patients with intracerebral hematomas (ICHs), including systolic blood pressure (SBP), Glasgow Coma Scale (GCS), and neurological deterioration (ND), defined as GCS score worsening ≥2 points, has been reported, though relationships among the prehospital information and clinical factors, including the spot sign, which was a reported predictor of outcomes, were not clarified. The purpose of this study was to elucidate relationships among prehospital information, the spot sign, and clinical outcomes after admission using multivariate analysis. Consecutive patients with ICHs admitted within 6 h of onset from 2009 to 2017 were investigated. Among 645 eligible patients, prehospital ND was found in 107 (16.6%). Multiple regression analysis showed that predictors of hematoma volume were prehospital GCS (p < 0.0001), prehospital ND (p < 0.0001), anticoagulant use (p = 0.0254), and cortical hematoma (p < 0.0001). Predictors of emergency surgery or death within 24 h were prehospital SBP (p = 0.0005, unit OR: 1.01), prehospital GCS (p < 0.0001, unit OR: 0.82), prehospital ND (p = 0.0002, OR: 3.26), and hematoma volume (p < 0.0001, unit OR: 1.04). Predictors of death at discharge were prehospital GCS (p < 0.0001, unit OR: 0.75), prehospital ND (p = 0.0001, OR: 3.49), and age (p = 0.0008, unit OR: 1.036). On the other hand, none of the 3 items of prehospital information were predictors of the spot sign or hematoma enlargement. The prehospital information and the spot sign could predict post-admission outcomes in a complementary fashion. Prehospital information might be used as a reference for preparing emergency treatment, as well as possible future blood pressure-lowering treatment, before emergency department arrival.

Neuroendoscopic Evacuation for Spontaneous Cerebellar Hemorrhage Is a Safe and Secure Approach and May Become a Mainstream Technique.

Patients with spontaneous cerebellar hemorrhage present with rapidly deteriorating neurological symptoms due to a hematoma-induced mass effect in the brainstem. We compared the standard surgical approach of a suboccipital craniectomy with neuroendoscopic surgery for treating spontaneous cerebellar hemorrhage. We performed a retrospective analysis of 41 patients indicated for surgery to treat spontaneous cerebellar hemorrhage. At our hospital, craniectomy was performed until 2010, and neuroendoscopic surgery was performed thereafter when a qualified surgeon was available. Duration of surgery and intraoperative blood loss were lower in the neuroendoscopic surgery group. The extent of hematoma removal and the percentage of patients requiring shunting were similar between groups. The mass effect was resolved in all patients in both groups, and no substantial re-bleeding was observed in either group. The outcomes at discharge were comparable between the two groups. Our surgeons used the supine lateral position, which involves fewer burdens to the patient than the prone position. Selection of the site of the burr hole is important to avoid the midline and to avoid the area exactly above the transverse and sigmoid sinus. Our results suggest that minimally invasive neuroendoscopic surgery is safe and superior to craniectomy due to shortened duration of surgery and decreased intraoperative bleeding.

Rare Lesions of the Internal Auditory Canal.

BACKGROUND: Approximately 95% of tumors occurring within the internal auditory canal (IAC) are vestibular schwannomas. Many undergo stereotactic radiation without definitive tissue diagnosis. Rare IAC tumors are not all radiosensitive and are poorly described. METHODS: Between 1992 and 2015, 289 consecutive patients with IAC lesions operated on were reviewed retrospectively. RESULTS: Fifteen patients (5.2%) (16 operations) had unusual histologic findings, including nonvestibular schwannomas (2 facial schwannomas, 2 cochlear schwannomas, 2 intermedius schwannomas), 3 meningiomas, 3 cavernous hemangiomas, a mucosa-associated lymphoid tissue lymphoma, an arachnoid cyst, and a lipochoristoma. None of these rare tumors could be identified before surgery. Three operative approaches were used: the retrosigmoid approach, middle fossa subtemporal approach, or translabyrinthine approach. Few complications occurred, including facial nerve palsy, loss of hearing, and vestibular function. Five-year average follow-up revealed one patient with recurrence. CONCLUSIONS: Clinical examination and imaging alone were insufficient to correctly identify these tumors. Definitive pathologicdiagnosis should be strongly considered to help tailor treatment.

Mutated p53 gene encodes a nonmutated epitope recognized by HLA-B*4601-restricted and tumor cell-reactive CTLs at tumor site.

Mutations of p53 gene occur in approximately 50% of human cancers, and accumulated p53 protein may be an appropriate target molecule to use for cancer immunotherapy. Indeed, mutated or nonmutated p53-derived peptides can induce HLA class I-restricted and tumor cell-reactive CTLs in vitro. However, to our knowledge, evidence that p53-derived peptides are truly recognized by CTLs at tumor sites has not yet been obtained. This study revealed that a mutated p53 gene encoded a nonmutated nonapeptide recognized by a HLA-B46-restricted and tumor cell-reactive CTL line that was established from T cells infiltrating a colon cancer lesion with the p53 mutation. This p53 peptide, at amino acid positions 99-107, had the ability to induce HLA-B46-restricted and peptide-specific CTLs reactive to tumor cells with the p53 mutation from the peripheral blood mononuclear cells of cancer patients, but not from those of healthy donors. These peptide-induced CTLs did not react to either HLA-B46(+) tumor cells without the p53 mutation or to HLA-B46(+) phytohemagglutinin-blastoid cells. These results provide a scientific basis for the development of p53-directed specific immunotherapy for HLA-B46(+) cancer patients.

Extradural Dermoid Cyst of the Anterior Infratemporal Fossa. Case Report.

Dermoid cysts are rare in the skull base. There have been 10 reported cases of dermoid cysts in the cavernous sinus, two in the petrous apex, and one in the extradural Meckel cave. This is the first case report of a dermoid cyst in the anterior infratemporal fossa attached to the anterior dura of the foramen ovale. The clinical presentation, radiologic findings, histologic features, tumor origin, and operative technique are described along with a review of the literature.

Surgical management of nonvascular lesions around the oculomotor nerve.

OBJECTIVE: Schwannomas originating from the oculomotor nerve are extremely rare. We report our experience in the management of oculomotor schwannomas and other lesions mimicking them, and discuss operative strategy for these rare tumors emphasizing oculomotor nerve preservation. METHODS: The clinical records of our patients and all those reported in the literature focusing on oculomotor schwannomas were reviewed and analyzed. The clinical presentations, operative approaches, complications, and results were studied. RESULTS: Between 1983 and 2010, six patients with primary oculomotor nerve lesions were treated. Three of them had schwannomas. Two others had pathologies that mimicked an oculomotor schwannoma and one was suspected as schwannoma. In the literature there were 55 previous cases of oculomotor schwannomas reported (surgical treated, 41 cases; observed, 9; gamma knife surgery treated, 2; autopsy, 3). Patients presented most commonly with diplopia, followed by headache and ptosis as initial symptoms. Out of 55 patients including the present 3 cases (3 autopsy cases were excluded), 30 patients (54.5%) finally developed oculomotor nerve palsy. Fifteen of 44 patients (34.1%) who underwent surgery developed persistent postoperative oculomotor palsy. Among them, 6 patients developed total palsy after surgery. Five of 12 patients (41.7%) who did not undergo surgery also developed oculomotor palsy. Oculomotor schwannomas most often grow its cisternal segment (48.3%) followed by intracavernous (39.6%) and cisternocavernous segments (12.1%). CONCLUSION: The microsurgical resection of oculomotor schwannomas carries a risk of worsening preoperative oculomotor nerve function; however, this is often transient. Considerable technical training and microanatomical knowledge of the region is required to optimize outcome.