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Background: Abducens nerve (AN) schwannomas are extremely rare tumors. Clinical characteristics and factors that influence postoperative outcomes are not well defined., Objective: To characterize clinical features of AN schwannomas and predictors of surgical outcomes., Methods: PRISMA-guided systematic review of the literature on AN schwannomas was performed. Subsequently, univariate and multivariate regression analyses were performed to identify the predictive value of variables that influence postoperative outcomes., Results: A total of 42 studies with 55 patients were evaluated. The mean age at presentation was 43.9 ± 14.6 years. The most common presenting symptom was cranial nerve VI palsy (69.1%). Cavernous sinus (49.1%) and prepontine cistern (36.3%) were the most commonly involved locations. Complete recovery after surgery was seen in 36.3% at a median follow-up of 28.4 ± 25.8 months. Preoperative AN palsy (P < 0.001), suboccipital approach (P = 0.007), and subtotal resection of tumor (P = 0.044) were significant protective factors for postoperative complications. Prepontine location and postoperative complications were poor prognostic indicators of AN recovery (odds ratio [OR], 0.10, P = 0.030 and OR, 0.10, P = 0.028, respectively). Subtotal resection was significantly correlated with higher odds of AN recovery (OR, 6.06; P = 0.040)., Conclusions: AN schwannomas are rare but serious tumors that can cause significant morbidity, with only approximately one third of patients showing complete recovery after surgery. The suboccipital approach was a protective factor for postoperative complications, especially when combined with subtotal resection. Knowledge of these factors along with tumor characteristics helps optimize surgical planning and preoperative counseling., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Abducens nerve palsy is a severe dysfunction after petroclival meningioma (PC MNG) surgery. The objective of this investigation was to analyze abducens nerve outcomes in patients who underwent the retrosigmoid approach in relation to the MIB-1 index. Thirty-two patients with primary sporadic PC MNG were retrospectively analyzed. Mean follow-up was 28.0 months. Analysis of the MIB-1 index was performed to evaluate the abducens nerve outcome. An optimal MIB-1 index cut-off value (<4/≥4) in the association with postoperative CN VI palsy was determined by ROC analysis (AUC: 0.74, 95% CI: 0.57−0.92). A new-onset CN VI palsy was present in 7 cases (21.88%) and was significantly associated with an increased MIB-1 index (≥4%, p = 0.025) and a peritumoral edema in the brachium pontis (p = 0.047) which might be caused by the increased growth rate. Tumor volume, cavernous sinus infiltration, auditory canal invasion, and Simpson grading were not associated with new CN VI deficits. Six (85.7%) of the 7 patients with both an increased MIB-1 index (≥4%) and new abducens nerve palsy still had a CN VI deficit at the 12-month follow-up. A peritumoral edema caused by a highly proliferative PC MNG with an elevated MIB-1 index (≥4%) is associated with postoperative abducens nerve deficits.

Objectives: While abducens nerve palsy (ANP) is a known risk in the setting of some endoscopic endonasal skull base surgery (ESBS), frequency and prognosis of post-operative palsy remain unknown. Our goals were to determine the frequency and prognosis of ANP after high-risk ESBS, and identify factors associated with recovery., Methods: Retrospective case series of all patients with pathology at highest risk for abducens nerve injury (pituitary adenoma, chordoma, meningioma, chondrosarcoma, cholesterol granuloma) generated a list of patients with abducens nerve palsy after ESBS performed from 2011-2016. A validated ophthalmologic clinical grading scale measuring lateral rectus duction from 0 to -5 (full motion to inability to reach midline) was measured at multiple time points to assess recovery of ANP., Results: Of 655 patients who underwent ESBS with increased risk of abducens injury, 40 (6.1%) post-operative palsies were identified and 39 patients with dedicated examination at multiple time points were included in subsequent analysis. Complete resolution was noted in 25 patients (64%) within 12 months. While 19 of 23 (83%) with a partial palsy had complete resolution, only six of 16 (38%) with a complete palsy resolved entirely (P = .005; Fisher's exact test). All six patients with delayed onset of palsy resolved (P = .070; Fisher's exact test). Meningioma and chordoma had higher rates of both temporary and permanent post-operative ANP (P < .0001; Fisher's exact)., Conclusions: The frequency of post-operative ANP following ESBS is low, even in high-risk tumors. While only a minority of complete abducens nerve palsies recover, patients with partial or delayed palsy post-operatively are likely to recover function without intervention., Level of Evidence: IV Laryngoscope, 131:513-517, 2021., (© 2020 American Laryngological, Rhinological and Otological Society Inc, "The Triological Society" and American Laryngological Association (ALA).)

Background: Abducens nerve function seldom shows complete recovery after removal of abducens nerve schwannoma. No cases with unclear course of the abducens nerve during surgery have been reported to achieve complete recovery of nerve function., Case Description: We report the case of a 44-year-old woman who presented with occasional dysgeusia without abducens nerve paresis. Magnetic resonance imaging showed a solid tumor about 2 cm in diameter at the left cerebellopontine cistern. Cranial nerves except the abducens nerve appeared intact. The tumor was removed via suboccipital craniotomy. The abducens nerve was totally invisible on the surface of the tumor throughout the procedure. Only short segments of abducens nerve were identifiable at around Dorello's canal and the root exit zone. The tumor was resected by subcapsular dissection, and part of the tumor capsule was preserved as a scaffold for nerve generation, although whether any abducens nerve was included remained uncertain. Histopathologic examination confirmed World Health Organization grade I schwannoma. Postoperatively, the patient presented with complete left abducens nerve paresis and diplopia, but abducens nerve function began to improve 3 months later and had completely recovered within 16 months after surgery., Conclusions: This represents the first description of abducens nerve schwannoma in which the course of the abducens nerve was intraoperatively unclear but complete recovery was achieved. In such cases, intentional subcapsular dissection may potentiate functional recovery., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Sixth-nerve palsy often develops as a result of trauma, neoplasm, or vascular disease affecting the pons. Less commonly, this palsy can be caused by pathology of the internal carotid artery in the cavernous sinus region. Here, we describe a rare case of spontaneous dissection of the internal carotid artery in the cavernous sinus accompanied by acute sixth nerve palsy that was successfully treated with surgery., Case Description: An 18-year-old man presented suddenly and spontaneously with isolated abducent nerve palsy. His magnetic resonance angiography identified a dissection of the right internal carotid artery in the cavernous sinus. We successfully treated it with high-flow bypass and ligation of the internal carotid artery (ICA)., Conclusions: Intracavernous ICA dissection is a possible cause of sixth nerve palsy. While most cases likely result from compromised arterial blood supply to the affected nerve, compression of the cranial nerves by the expanded artery can occur in some cases. Surgical treatment is a safe and effective option for relieving nerve compression after intracavernous ICA dissection., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Intraoperative neurophysiologic monitoring of the extraocular cranial nerve (EOCN) is not commonly performed because of technical difficulty and risk, reliability of the result and predictability of the postoperative function of the EOCN., Methods: We performed oculomotor nerve (CN III) and abducens nerve (CN VI) intraoperative monitoring in patients with skull base surgery by recording the spontaneous muscle activity (SMA) and compound muscle action potential (CMAP). Two types of needle electrodes of different length were percutaneously inserted into the extraocular muscles with the free-hand technique. We studied the relationships between the SMA and CMAP and postoperative function of CN III and CN VI., Results: A total of 23 patients were included. Nineteen oculomotor nerves and 22 abducens nerves were monitored during surgery, respectively. Neurotonic discharge had a positive predictive value of less than 50% and negative predictive value of more than 80% for postoperative CN III and CN VI dysfunction. The latency of patients with postoperative CN III dysfunction was 2.79 ± 0.13 ms, longer than that with intact CN III function (1.73 ± 0.11 ms). One patient had transient CN VI dysfunction, whose CMAP latency (2.54 ms) was longer than that of intact CN VI function (2.11 ± 0.38 ms). There was no statistically significant difference between patients with paresis and with intact function., Conclusions: The method of intraoperative monitoring of EOCNs described here is safe and useful to record responses of SMA and CMAP. Neurotonic discharge seems to have limited value in predicting the postoperative function of CN III and CN VI. The onset latency of CMAP longer than 2.5 ms after tumor removal is probably relevant to postoperative CN III and CN VI dysfunction. However, a definite quantitative relationship has not been found between the amplitude and stimulation intensity of CMAP and the postoperative outcome of CN III and CN VI.

Background: Limited or no literature exists identifying factors associated with functional nerve recovery in patients undergoing resection of sixth cranial nerve (CN VI) schwannomas., Methods: A systematic review of literature was performed on CN VI schwannomas that were treated surgically. Synthesizing the findings pooled from the literature, we investigated associations of patient demographics and clinical characteristics with postsurgical CN VI functional recovery in multivariable regression models. In addition, we present the findings of an adolescent woman surgically managed for intracavernous CN VI schwannoma. Complete encasement of the cavernous segment of the internal carotid artery is unique to our case., Results: We synthesized data of 32 patients from 29 studies, and our index case. Overall, the mean age of the patients was 44.0 ± 16.5 years, and approximately 52% (n = 17) were female. Most tumors were left-sided (n = 18; 54.5%), with an average size of 3.46 ± 1.71 cm. The most common location was cisternal (n = 11; 33%), followed by cavernous sinus (CS) proper (n = 9; 27%), cisterocavernous (n = 8; 24%), orbital (n = 4; 12%) and caverno-orbital (n = 1; 3%). CN VI recovery was reported in less than half the cohort (n = 14; 45%). Tumor extension in the CS was significantly associated with lesser likelihood (odds ratio [OR], 0.07; 95% confidence interval [CI], 0.01-0.98; P = 0.048) of postsurgical CN VI recovery. Although female gender (OR, 0.86; 95% CI, 0.07-10.09; P = 0.906), large tumor size (>2.5 cm) (OR, 0.45; 95% CI, 0.07-2.89; P = 0.397), and solid consistency (OR, 0.37; 95% CI, 0.03-4.19; P = 0.421) were associated with lesser odds for recovery, these were not statistically significant. Likewise, although gross total resection (OR, 6.28; 95% CI, 0.33-118.25; P = 0.220) was associated with higher odds of nerve recovery, the estimates were statistically insignificant., Conclusions: CS involvement is associated with lesser odds for functional nerve recovery in patients undergoing surgical resection for CN VI schwannoma., (Copyright © 2017. Published by Elsevier Inc.)

One of the most important and useful pieces of information in the preoperative evaluation of a large petroclival meningioma is the running course of the abducens nerve. The abducens nerve is small and has a long intracranial course, making it prone to compression by the tumor at various anatomical points. In relatively large tumors, it is difficult to confirm the entire course of the abducens nerve, even by heavy T2-thin slice imaging. We report a case of successful preoperative estimation of the course of the abducens nerve that aided in its complete preservation during the resection of a large petroclival tumor.

Object: Extended endoscopic transnasal surgeries for skull base lesions have recently been performed. Some expert surgeons have attempted to remove tumors such as chordomas, meningiomas, and pituitary adenomas in the clival region using the transnasal approach and have reported abducens nerve injury as a common complication. There have been many microsurgical anatomical studies of the abducens nerve, but none of these studies has described an anatomical landmark of the abducens nerve in the transnasal approach. In this study the authors used cadaver dissections to describe Grüber's ligament as the most reliable landmark of the abducens nerve in the transnasal transclival view., Methods: The petroclival segment of the abducens nerve was dissected in the interdural space-which is also called Dorello's canal, the petroclival venous gulf, or the sphenopetroclival venous confluence-using the transnasal approach in 20 specimens obtained from 10 adult cadaveric heads., Results: The petroclival segment of the abducens nerve clearly crossed and attached to Grüber's ligament in the interdural space, as noted in the transnasal view. The average length of the dural porus to the intersection on the abducens nerve was 5.2 ± 1.0 mm. The length of the posterior clinoid process (PCP) to the intersection on Grüber's ligament was 6.4 ± 2.6 mm. The average width of Grüber's ligament at the midsection was 1.6 ± 0.5 mm., Conclusions: Grüber's ligament is considered a useful landmark, and it is visible in most adults. Thus, surgeons can find the abducens nerve safely by visualizing inferolaterally along Grüber's ligament from the PCP.

The aim of this study is to demonstrate and review the detailed microsurgical anatomy of the abducens nerve and surrounding structures along its entire course and to provide its topographic measurements. Ten cadaveric heads were examined using ×3 to ×40 magnification after the arteries and veins were injected with colored silicone. Both sides of each cadaveric head were dissected using different skull base approaches to demonstrate the entire course of the abducens nerve from the pontomedullary sulcus to the lateral rectus muscle. The anatomy of the petroclival area and the cavernous sinus through which the abducens nerve passes are complex due to the high density of critically important neural and vascular structures. The abducens nerve has angulations and fixation points along its course that put the nerve at risk in many clinical situations. From a surgical viewpoint, the petrous tubercle of the petrous apex is an intraoperative landmark to avoid damage to the abducens nerve. The abducens nerve is quite different from the other nerves. No other cranial nerve has a long intradural path with angulations and fixations such as the abducens nerve in petroclival venous confluence. A precise knowledge of the relationship between the abducens nerve and surrounding structures has allowed neurosurgeon to approach the clivus, petroclival area, cavernous sinus, and superior orbital fissure without surgical complications., (Copyright © 2012 Wiley Periodicals, Inc.)

Simultaneous hemifacial spasm (HFS) and trigeminal neuralgia caused by cranial nerve (CN) compression from a tortuous basilar artery (BA) is very rare. We report a case of a 66-year-old man who presented with both HFS and "atypical" trigeminal neuralgia. The patient had a tortuous BA compressing both CN V and VII. The patient underwent microvascular decompression after failing conservative medical management. To the best of our knowledge this is the first reported case of both HFS and "atypical" trigeminal neuralgia that were both successfully treated by surgical intervention. We report the management of this rare combination and review the literature.

Objective: To clarify the oriented classification, relationships, and variations of the abducens nerve and provide a detailed description of its microsurgical anatomic features., Methods: A microsurgical anatomic dissection of the abducens nerve was performed in 100 specimens obtained from 50 adult cadaveric heads fixed in formalin and two adult cadaveric heads stained with hematoxylin and eosin for histological examination. Important neurovascular and structural relationships of the abducens nerve were observed., Results: The abducens nerve was divided into five segments (cisternal, petroclival, internal carotid artery, fissural, and intraconal). It coursed in the petroclival venous confluence and there was a complex anatomic relationship. Two new types of abducens nerve variations were found. In one type, the duplicated nerve is split into two branches for a limited length in the cavernous sinus (CS). The other is a complex type, which has a complex course and pattern. This type of duplicated abducens nerve has a communicating branch in the cistern and numerous fasciculi in the CS. In addition, the two branches do not accompany each other for the entire course in the CS., Conclusion: The vulnerability of the abducens nerve results from diverse factors. The inferolateral trunk, which arises from the intracavernous segment of carotid artery (also called the artery of the inferior CS), is an important landmark for finding the abducens nerve and sympathetic nerve. Variations of the abducens nerve are not rare. Keeping variations of the nerve in mind is important during skull base operations and transvenous endovascular interventions. Understanding the relationship of the abducens nerve with adjacent structures will help us in preparing for safe surgery.

Aim: Surgical approaches to Meckel's cave (MC) are often technically difficult and sometimes associated with postoperative morbidity. The relationship of surgical landmarks to relevant anatomy is important. Therefore, we attempted to delineate quantitatively their anatomy and the relationships between MC and surrounding structures., Material and Methods: With the aid of a surgical microscope, MC and its contents were studied in 15 formalin-fixed cadaver head specimens. Measurements were made and their relationships were observed., Results: The distance from the zygomatic arch and the lateral end of the petrous ridge to MC was 26.5 and 34.4 mm, respectively. The distance from the arcuate eminence, the facial nerve hiatus, and the foramen spinosum to MC was 16.6, 12.8 and 7.46 mm respectively. The TG lay 5.81 mm posterior to the foramen ovale. The distance from the abducens, trochlear and oculomotor nerves to the trigeminal ganglion was 1.87, 5.53 and 6.57 mm respectively. The distance from the posterior and the anterior walls of the sigmoid sinus to the trigeminal porus was 43.6 and 33.1 mm respectively. The trigeminal porus was on average 7.19 mm from the anterior wall of the internal acoustic meatus., Conclusion: The anatomical landmarks as presented herein regarding MC may be used for a safer skull base approach to the region.

Background and Importance: A cavernous hemangioma arising from the abducens nerve has not been previously reported in the literature. Based on the surgical experience with this case, the authors discuss the clinical importance and resectability potential of a duplicated abducens nerve., Clinical Presentation: A 54-year-old woman presented with a recurrence of diplopia that had occurred 3 years before this admission and had spontaneously resolved without any specific treatment. On admission, there were no specific neurological deficits. Magnetic resonance imaging revealed a cone-shaped mass on the right anterior cerebellopontine angle with hemorrhagic change. Surgical resection via a standard right lateral suboccipital approach was performed. A cystic mass was found emerging from the entry zone of the Dorello canal and encircling the larger branch of the duplicate abducens nerve. Because there was no demarcation between the mass and origin branch, both were removed en bloc. Pathology revealed the presence of a cavernous hemangioma mixed with nerve tissue. Despite preserving a small branch of the duplicate abducens nerve, the patient had permanent right abducens palsy., Conclusion: A cavernous hemangioma arising from the abducens nerve should be suspected as a possible diagnosis for a cystic mass on the anterior cerebellopontine angle. Although duplication of the abducens nerve has not been clearly confirmed on clinical grounds, sacrificing the larger branch during surgery may lead to permanent abducens palsy, as in our case.

Aim: Knowing the distance between the superior and inferior border of Parkinson's triangle and the location of the abducent nerve within the cavernous sinus is important to decrease the complications which may occur during surgery. We aimed to investigate the cavernous sinus to decrease the complications that may occur during surgery to this area., Material and Methods: Fifty MRIs without pituitary gland abnormality were chosen for radiological assessment of CS. These images were from 18 males and 32 females, with ages ranging from 9 to 58 years and a median age of 28 years. We evaluated structures within and on the lateral wall of the cavernous sinus (especially Parkinson's triangle) with magnetic resonance imaging. The position of the abducent nerve and its level according to the cranial nerves running close the lateral wall were examined., Results: At the level of pituitary stalk, the distance between the trochlear nerve and the ophthalmic nerve ranged from 1 to 4 mm bilaterally. The abducent nerve was located between the trochlear and the ophthalmic nerves in 30% cases bilaterally., Conclusion: The knowledge of the position of the abducent nerve will provide a great benefit in minimizing the rate of complications that may occur during the resection of tumors of the cavernous sinus.

Purpose: To describe the causes and treatment of sixth (abducens) nerve palsy in a series of pediatric patients., Methods: This was a 14-year retrospective study of sixth nerve palsy in children under 14 years of age. Outcomes studied included horizontal deviation, degree of limitation of abduction, and head turn. Patients were treated with botulinum toxin injection at the time of diagnosis; surgery was indicated if treatment with botulinum toxin was unsuccessful. Success was defined as final deviation of orthotropia with no head turn or diplopia., Results: Sixth nerve palsy was diagnosed in 15 patients (10 boys; mean age, 4.1 years) between 1995 and 2008. Involvement was bilateral in 2 cases and unilateral in 13 (7 right eyes). Causes included neoplasm (4 cases), trauma (2), idiopathic (3), congenital (2), viral (2), and inflammatory (1). Neoplastic causes were associated with other neurologic signs. Recovery was spontaneous in 5 cases (2 idiopathic, 1 traumatic, 1 congenital, and 1 inflammatory). Botulinum toxin was successful in 7 of 10 patients treated, with follow-up surgery required in the remaining 3 cases. The final result was good in all cases. In all 15 patients, mean time from diagnosis to resolution was 39 months (range, 5 to 170 months)., Conclusions: Neoplasms were the most frequent cause of sixth nerve palsy in our patient population. Recovery was spontaneous in one third of the patients. Most required treatment with botulinum toxin, which was successful in most cases. Surgery was successful after a single procedure., (Copyright © 2010 American Association for Pediatric Ophthalmology and Strabismus. Published by Mosby, Inc. All rights reserved.)

Aim: The microanatomy of the abducens nerve (AN) is important for clinical reasons and surgical approaches as it is located in the petroclival region. The incidence of branching and duplication of the abducens nerve are unknown and mechanisms relating to paralysis of the nerve in indirect conditions are yet to be clarified., Material and Methods: Microanatomical details (anatomical observations and morphometric measurements) of the AN were obtained from 20 cadaveric skull bases (40 specimens)., Results: 55% of the intracranial abducens nerves had branching, with type 2 and 3 branching occurring in 10%. The nerve coursed below the petrosphenoidal ligament in all but one, and was located at the lateral third below the ligament in 82.5% of the specimens. The mean AN diameter was 1.3±0.2 mm, and the mean diameter of the dural entrance pore was 1.8±0.3 mm, the right being significantly larger than the left. The mean distance of the AN from the posterior clinoid process was 8.4±2.5 mm and from the petrous apex 3.6±2.1 mm., Conclusion: Branching of the AN was present in a significant number of specimens; the branching pattern at the cavernous segment may be called "pseudobranching". The AN is at risk for paresis in indirect conditions because of its angles and fixations on its course.

Background: Understanding the course of the most medially located parasellar cranial nerve, the abducens, becomes critical when performing an expanded endonasal approach., Objective: We report an anatomoclinical study of the abducens nerve and describe relevant surgical nuances to avoid its injury., Methods: Ten anatomic specimens were dissected using endoscopes attached to an high-definition camera. A series of anatomic measurements and relationships of the abducens nerve were noted. Illustrative clinical cases are described to translate those findings into practice., Results: Cisternal, interdural, gulfar, and cavernous segments of the abducens were identified intracranially. The mean distance from the vertebrobasilar junction (VBJ) to the pontomedullary sulcus (PMS) was 4 mm; horizontal distance between both abducens nerves at the PMS was 10 mm, and between both abducens at the interdural segment was 18.5 mm. The upper limit of the lacerum segment of the internal carotid artery was at the same level of the dural entry point of the sixth cranial nerve posteriorly. The sellar floor at the sphenoid sinus marks the level of the gulfar segment in the craniocaudal axis. At the superior orbital fissure, the abducens nerve and V2 were at an average vertical distance of 11.5 mm., Conclusion: Anatomic landmarks to localize the abducens nerve intraoperatively, such as the VBJ for the transclival approach, the lacerum segment of the carotid, and the sellar floor for the medial petrous apex approach, and V2 for Meckel's cave approach, are reliable and complementary to the use of intraoperative electrophysiological monitoring.

Objective: Nerve-grafting surgery after resection of neuro-vascular bundles during radical prostatectomy is one of the promising resolutions for dilemma between cancer control and functional preservation. The objective of this study is to evaluate the effect of nerve-grafting surgery on health-related quality of life (HRQOL) in localized prostate cancer patients with special interest in the influence of sexual dysfunction on mental status., Methods: A total of 88 patients followed for a minimum of 12 months after surgery with a median follow-up of 48 months were enrolled in this study. Of those, 24 patients underwent unilateral nerve-sparing with contralateral nerve-grafting or bilateral nerve-grafting and 64 patients underwent prostatectomy without nerve-sparing procedure. HRQOL assessed with the Japanese version of Extended Prostate Cancer Index Composite (EPIC) and Medical Outcomes Study 8 Items Short Form Health Survey (SF-8) was analyzed cross-sectionally., Results: Patients in nerve-grafting group who recovered potency demonstrated higher sexual function scores compared with those without nerve-sparing procedure (P = 0.022 and 0.001 in 25-48 and 49 months or later, respectively). However, sexual bother scores in nerve-grafting group who recovered potency were lower than those without nerve-sparing procedure throughout the observation periods (P = 0.012 in 49 months or later)., Conclusions: Cavernous nerve reconstruction provided recovery of erectile dysfunction in substantial proportion of patients, which resulted in favorable physical HRQOL. Majority of these patients, however, did not seem to be satisfied with their sexual function, which caused sustained sexual bother feeling.

Schwannomas of the abducens nerve are extremely rare tumors affecting cavernous, cisternal or both segments of sixth cranial nerve. Clinical features and neuroradiological imagery are frequently insufficient to reach an accurate pre-operative diagnosis. We report a patient with a cystic tumor with ring-like contrast enhancement at the right anterior pontomesencephalic junction. Radical excision was performed via anterior transpetrosal approach and showed an extrinsic tumor originating from the sixth nerve. A postoperative sixth nerve palsy had disappeared completely 9 months after the surgery. The correct diagnosis of an abducens nerve schwannoma is established by the intraoperative finding of a tumor attachment to the sixth nerve and by histopathological analysis. The various differential diagnoses, the clinical and radiological features of this diagnosis and management are issues discussed in this illustrated review.

Background: The clinical course of abducens nerve palsy associated with skull base tumour is rarely reported. In this study, we examined the post-operative course of abducens nerve palsies associated with various skull base tumours., Method: Between January 2003 and December 2006, 240 patients with various skull base tumours underwent surgery at Kyushu University Hospital. Among them, nine patients presented with abducens nerve palsies (ten nerves) following surgery. The conditions included two pituitary adenomas, two trigeminal schwannomas and five meningiomas. We evaluated the function of the abducens nerves in these patients on admission, at discharge, and periodically in the outpatient clinic., Findings: Four of the abducens nerve palsies already existed prior to surgery, and six of them developed post-operatively. In the four patients with pituitary adenomas and trigeminal schwannomas, all nerves were anatomically preserved and showed complete recovery of function within 6 months after surgery. In contrast, only two of the six palsies in patients with skull base meningiomas showed complete recovery. In three patients with petro-clival meningiomas, the abducens nerves were completely transected during surgery, and one was reconstructed using fibrin glue. This patient remarkably recovered from the abducens nerve palsy within 2 years., Conclusions: The abducens nerve palsies in pituitary adenomas and trigeminal schwannomas showed a better clinical course compared to those in skull base meningiomas. The abducens nerve palsies that occur with skull base meningiomas are less likely to recover. Nevertheless, it is important to preserve the nerves and to perform surgical repair if the nerve is transected.

Case Report: A case of isolated schwannoma of the orbit, arising from the terminal branches of the abducens nerve to the lateral rectus muscle, is reported. The patient presented with a painless proptosis of the left eye., Discussion: Preoperative diagnosis of benign intraorbital neoplasm was made by means of CT and MR scans; the mass was radically excised through a microsurgical lateral orbitotomy and the pathological examination revealed a schwannoma. Features of orbital schwannoma are described, together with some details concerning the surgical strategy and the history of the evolution of the lateral orbitotomy.

Isolated abducent palsy is a symptom that can be caused by many different intracranial pathological conditions. In this report the authors describe the case of a patient who suffered isolated abducent palsy resulting from vascular compression of the sixth cranial nerve; surgical treatment consisted of microvascular decompression (MVD). This 56-year-old man presented with short-lasting episodes of a pulling sensation at the lateral side of his right eye associated with intermittent diplopia, followed by a progressive palsy of the abducent nerve and constant diplopia. Magnetic resonance imaging revealed a neurovascular contact of a dolichoectatic basilar artery with the abducent nerve. The patient underwent surgery consisting of a combined supra- and infratentorial presigmoid approach and subsequent MVD of the abducent nerve. Postoperatively, the abducent nerve palsy resolved within days, and the patient remains free of symptoms with a follow-up time of 4 years. This is the first report of a neurovascular compression of the abducent nerve treated successfully by MVD.

Background: The central and peripheral nervous systems participate in several local physiological and pathological processes. There is experimental evidence that the inflammatory, local immune, and wound healing responses of a tissue can be modulated by its innervation. The aim of this clinical report is to present a case of unilateral severe periodontitis associated with ipsilateral surgical resection of the fifth, sixth, and seventh cranial nerves and to discuss the possible contribution of the nervous system to periodontal pathogenesis., Methods: A 39-year-old female patient with a history of a cerebrovascular accident caused by a right pontine arteriovenous malformation and destruction of the right fifth, sixth, and seventh cranial nerves was diagnosed with severe chronic periodontitis affecting only the right maxillary and mandibular quadrants. The patient's oral hygiene was similar for right and left sides of the mouth. Percentages of tooth surfaces carrying dental plaque were 41% and 36% for right and left sides, respectively. Non-surgical and surgical periodontal therapy was performed, and the patient was placed on a regular periodontal maintenance schedule., Results: Healing following initial periodontal therapy and osseous periodontal surgery occurred without complications. Follow-up clinical findings at 1 year revealed stable periodontal health., Conclusions: This case report suggests that periodontal innervation may contribute to the regulation of local processes involved in periodontitis pathogenesis. It also suggests that periodontal therapy can be performed successfully at sites and in patients affected by paralysis.

Background: Moebius sequence is a rare congenital absence of the sixth and seventh cranial nerves, although there may be additional congenital cranial neuropathies. Developmental delay, cardiac and musculoskeletal abnormalities may also co-exist. Oro-facial manifestations include bilateral facial nerve palsy resulting in a mask like facies, drooling, incomplete eye closure, and strabismus secondary to the extra-ocular muscle imbalance. This condition has multiple implications for anesthetic care., Methods: We reviewed 111 anesthesia records of 46 patients with Moebius sequence for anesthesia technique and related complications., Results: Facial nerve palsy was universally present and bilateral in 44 (93.6%) patients. Thirty-two (68%) had concomitant sixth nerve palsy. Oro-facial and limb abnormalities were present in 16 (35%) and 18 (39%) of patients respectively. Endotracheal intubation, when attempted, was easy in 76 of 106 cases. Tracheal intubation was consistently difficult in seven patients and intubation failure occurred in a single patient only. Statistically significant factors associated with difficult tracheal intubation included structural abnormalities of the mandible and palate and abnormalities of four cranial nerves (IX, X, XI, XII)., Conclusion: We confirm that tracheal intubation may be difficult in patients with Moebius sequence. We identify disease features that might predict a difficult tracheal intubation and thus allow the anesthesiologist an opportunity to plan accordingly.

In the last decades, there have been many efforts directed to gain a better understanding on adult neuron-target cell relationships. Embryonic grafts have been used for the study of neural circuit rewiring. Thus, using several donor neuronal tissues, such as cerebellum or striatum, developing grafted cells have been shown to have the capability of substituting neural cell populations and establishing reciprocal connections with the host. In addition, different lesion paradigms have also led to a better understanding of target dependence in neuronal cells. Thus, for example, axotomy induces profound morphofunctional changes in adult neurons, including the loss of synaptic inputs and discharge alterations. These alterations are probably due to trophic factor loss in response to target disconnection. In this review, we summarize the different strategies performed to disconnect neurons from their targets, and the effects of target substitution, performed by tissue grafting, upon neural properties. Using the oculomotor system-and more precisely the abducens internuclear neurons-as a model, we describe herein the effects of disconnecting a population of central neurons from its natural target (i.e., the medial rectus motoneurons at the mesencephalic oculomotor nucleus). We also analyze target-derived influences in the structure and physiology of these neurons by using cerebellar embryonic grafts as a new target for the axotomized abducens internuclear neurons.

Background: Some patients with acquired horizontal gaze palsy overcome the adduction palsy by utilizing convergence. This substitution phenomenon is very rare. We report a patient with horizontal gaze palsy who was able to use convergence to compensate for the lack of adduction in the left eye., Case: The patient was a 31-year-old woman with an arteriovenous malformation in the fourth ventricle. She suffered right gaze palsy and right abducens palsy after tumor surgery and radiation therapy., Observations: Three years after the vascular accident, she was found to be able to adduct the left eye, in association with the adduction of the right eye. At the same time, constriction of both pupils and globe retraction of the left eye were observed. When she shifted the gaze direction of her left eye from left to right, an 11 and 8 diopter increase of myopia in the right and left eyes, respectively, was confirmed by objective refractometry., Conclusions: The existence of convergence substituting for adduction in this patient with horizontal gaze palsy was confirmed by refraction change in addition to pupillary change.

Background: Only 2 cases of abducens nerve schwannoma solely inside the cavernous sinus have been reported. In both cases, abducens nerve palsy remained after operation. We report the first case of abducens nerve schwannoma inside the cavernous sinus proper with postoperative recovery from abducens nerve palsy., Case Description: The patient was a 47-year-old female who developed left abducens and trigeminal nerve palsies. Neuroradiological examination revealed left intra-cavernous sinus tumor. Total removal of the tumor was performed. The location of the tumor was confirmed intraoperatively inside the cavernous sinus itself, with no relation to the trigeminal nerve. Further, the relation of the tumor to one particular nerve fiber within the abducens nerve bundle was confirmed inside the cavernous sinus. After surgery, the patient had transient abducens nerve palsy. It had totally disappeared by 6 months., Conclusion: When the tumor origin is just within the spacious cavernous sinus rather than more posterior in the narrow dural tunnel of Dorello's canal, successful preservation of the nerve function is possible postoperatively through a thorough knowledge of the membranous anatomy and careful preoperative study of the radiographic findings.

Objective: To anatomically reconstruct the oculomotor nerve, trochlear nerve, and abducent nerve by skull base surgery., Methods: Seventeen cranial nerves (three oculomotor nerves, eight trochlear nerves and six abducent nerves) were injured and anatomically reconstructed in thirteen skull base operations during a period from 1994 to 2000. Repair techniques included end-to-end neurosuture or fibrin glue adhesion, graft neurosuture or fibrin glue adhesion. The relationships between repair techniques and functional recovery and the related factors were analyzed., Results: Functional recovery began from 3 to 8 months after surgery. During a follow-up period of 4 months to 6 years, complete recovery of function was observed in 6 trochlear nerves (75%) and 4 abducent nerves (67%), while partial functional recovery was observed in the other cranial nerves including 2 trochlear nerves, 2 abducent nerves, and 3 oculomotor nerves., Conclusions: Complete or partial functional recovery could be expected after anatomical neurotization of an injured oculomotor, trochlear or abducent nerve. Our study demonstrated that, in terms of functional recovery, trochlear and abducent nerves are more responsive than oculomotor nerves, and that end-to-end reconstruction is more efficient than graft reconstruction. These results encourage us to perform reconstruction for a separated cranial nerve as often as possible during skull base surgery.

Axotomy produces changes in the electrical properties of neurons and in their synaptic inputs, leading to alterations in firing pattern. We have considered the possibility that these changes occur as a result of the target deprivation induced by the lesion. Thus, we have provided a novel target to axotomized central neurons by grafting embryonic tissue at the lesion site to study the target dependence of discharge characteristics. The extracellular single-unit electrical activity of abducens internuclear neurons was recorded in the alert behaving cat in control, after axotomy, and after axotomy plus the implantation of cerebellar primordium. As recently characterized (de la Cruz et al. [2000] J. Comp. Neurol. 427:391-404), firing alterations induced by axotomy included an overall decrease in firing rate and a loss of eye-related signals, i.e., eye position and velocity neuronal sensitivities, that do not resume to normality with time. The grafting of a novel target to the injured abducens internuclear neurons restored the normal firing and sensitivities as recorded in the majority of units. To study the reinnervation of the implant, we performed anterograde labeling with biocytin combined with electron microscopy visualization. Axons of abducens internuclear neurons grew into the transplant sprouting into granule cell and molecular layers, as characterized by the immunostaining for gamma-aminobutyric acid and calbindin D-28k. Ultrastructural examination of labeled axons and boutons revealed the establishment of synaptic contacts, mainly axodendritic, with different cell types of the grafted cerebellar cortex. Therefore, these data indicate that axotomized central neurons resume to normal firing after the reinnervation of a novel target., (Copyright 2002 Wiley-Liss, Inc.)

We present a case of an adolescent with a giant intracranial granular-cell tumor, who presented with diplopia and worsening visual acuity. The tumor measured 8.2 cm at the maximum diameter and occupied the right middle cranial fossa, with intrasellar and suprasellar involvement. It was composed of solid nests of oval or polygonal eosinophilic cells with a focal pseudo-papillary configuration. Pituitary macroadenoma was suspected from examination of the intraoperative frozen section, but immunohistochemical and ultrastructural findings were consistent with granular-cell tumor, and they suggested the origin to be the peripheral nerve sheath. Considering that abducens palsy was the first clinical manifestation, the tumor was thought to arise from abducens. From histological findings (focal cellular spindling, mitotic activity and a relatively high Ki-67 labeling index [10.1%]) and according to Fanburg-Smith's criteria, the tumor was suspected to have low-grade malignant potential. Granular-cell tumor should be included in the differential diagnosis of parasellar tumors, even in young patients or patients with large lesions. Both immunohistochemical and electron microscopic studies are essential for diagnosis.

Some thoughts on current interpretations of available data regarding vestibular compensation at functional, network, and neural levels are presented. Basic concepts related to neural plasticity (or elasticity) underlying motor learning and regeneration also are discussed briefly. Modifiability in vestibular pathways, at both the functional and structural levels, after peripheral and central axotomy, and subsequent to transient or permanent chemical target removal, is presented as an experimental ground to explain similarities and differences between regenerative, compensatory, and adaptive mechanisms in the mammal central nervous system.

A 47-year-old male presented with abducens nerve palsy due to basilar impression associated with atlanto-occipital assimilation manifesting as slowly progressive bilateral trigeminal neuralgia and diplopia in the right lateral gaze. X-ray and computed tomography of the skull confirmed the diagnosis of basilar impression and atlanto-occipital assimilation, and magnetic resonance imaging disclosed tightness of the posterior cranial fossa. Surgical suboccipital decompression resulted in gradual resolution of the patient's complaints, and no additional symptoms were recognized. Impairment of the sixth cranial nerve is a rare symptom compared to those of the fifth or the eighth cranial nerve in a patient with a craniocervical malformation. However, the present case shows the possibility of cranial nerve dysfunction due to tightness of the posterior cranial fossa, and suggests that surgical treatment for basilar impression with atlanto-occipital assimilation should be considered in patients with uncommon and unusual symptoms.

Objective and Importance: Results of surgical repair of the injured abducens nerve are rarely reported in the literature. A full functional recovery of a completely resected abducens root may be exceptional. We describe a patient who obtained normal ocular alignment and binocular vision after surgical reconstruction of a transected abducens nerve., Clinical Presentation: A 56-year-old woman with a petroclival meningioma was presented. She underwent total removal of the tumor through a combined supra/infratentorial transpetrosal approach. The abducens nerve was tightly attenuated by the tumor and thickened dura. During dissection, the nerve was completely transected just behind the entrance to Dorello's canal., Intervention: The abducens nerve was the single root type and inevitably required surgical repair. To obtain a sufficient length of the distal stump for trimming, part of the petrosphenoidal ligament was cut and the superior border of the petrous bone was exposed. The proximal stump of the nerve was also trimmed to obtain healthy tissue, and reconstruction was performed with five 10-0 nylon sutures. Five months later, esodeviation began to improve. Nine months after the surgery, the patient did not complain of diplopia and an objective assessment reported normal ocular alignment and estimated binocular function as "excellent" according to Biglan's system. Overcorrection of abduction did not occur., Conclusion: The result in our patient confirms the possibility of full functional recovery after surgical repair of a totally transected abducens nerve.

Objective and Importance: Tumors originating from the cranial nerves are uncommon, except for the acoustic and trigeminal neuromas. The sixth nerve, however, has the potential to generate neuromas with characteristic clinical features., Clinical Presentation: A 54-year-old woman presented with diplopia and increased intracranial pressure. Magnetic resonance imaging showed a large mass in the prepontine region. Surgery was performed via a condylar approach and demonstrated a tumor originating from the prepontine portion of the sixth nerve., Conclusion: The sixth nerve neuroma at the pontomedullary junction showed characteristic clinical features and could be successfully removed via a condylar approach.

Purpose/methods: We recently encountered anterior segment ischemia in a young healthy girl with traumatic abducens nerve palsy after the Jensen procedure and ipsilateral recession of the medial rectus muscle. The patient was treated with topical dexamethasone and homatropine 2% and oral prednisone., Results/conclusion: The patient's condition improved, and six weeks postoperatively, visual acuity was 20/20. As this complication of anterior segment ischemia is potentially serious and unpredictable, we think that an alternative surgical approach should be used when treating patients with muscle palsies.

Pachymeningitis manifested by localized enhancing dural thickening adjacent to the clivus on MR images of two patients with sphenoid sinusitis and sixth-nerve palsy is presented. This is an unusual complication of sphenoid sinusitis. Prompt diagnosis and therapy may avoid significant intracranial complications.

An anatomical study of three microsurgical intraorbital routes to the optic nerve and orbital apex, which can be reached through a fronto-orbital craniotomy, was conducted on cadaver specimens. The structures that could be exposed via the medial, central, or lateral approaches directed through the orbital roof were defined. The medial approach, directed through the space between the superior oblique and the levator muscles, provides good access to all parts of the intraorbital optic nerve. The central approach, between the levator and the superior rectus muscles, provides the shortest route to the optic nerve. Two variants of the central approach were examined. In the first, the levator muscle and frontal nerve are retracted medially and the superior rectus muscle laterally. This variant provides access to only the midportion of the intraorbital segment of the optic nerve. In the second variant, the frontal nerve is retracted laterally together with the superior rectus muscle. This variant provides access to the posterior two-thirds of the intraorbital portion of the optic nerve. The lateral approach is directed between the levator and lateral rectus muscles. This approach also has two variants, depending on whether the superior ophthalmic vein is retracted medially or laterally. The variant in which the superior ophthalmic vein is retracted medially with the levator and superior rectus muscles provides access to the lateral side of the optic nerve except in the region adjacent to the superior orbital fissure. The variant in which the superior ophthalmic vein is retracted laterally together with the lateral rectus muscle provides excellent access to the optic nerve in the region of the superior orbital fissure. It is an ideal approach for lesions that involve both the cavernous sinus and orbit.

Twenty-eight abducent nerves were examined after injecting india ink and gelatin into the vertebrobasilar arterial system. All the abducent nerves were found to be crossed and/or penetrated by the surrounding vessels. The ventral surface of the nerves was crossed by the anterior inferior cerebellar artery (AICA) (75.0%), the posterior inferior cerebellar artery (17.85%), the common trunk of the AICA and posterior inferior cerebellar artery (7.14%), the internal auditory artery (14.28%), the anterolateral artery (46.43%), the pontomedullary artery (92.86%), and the corresponding veins (46.43%). The dorsal surface of the cisternal segment was crossed by the AICA (35.71%), the inferolateral pontine artery (10.71%), the anterolateral artery (82.14%), and the certain veins (46.43%). Sixty-four percent of the cisternal segments were penetrated by one or more of the following vessels: the AICA (25.0%), the anterolateral artery (17.86%), the pontomedullary artery (3.57%), and/or by the corresponding veins (42.86%). The majority of the cisternal segments of the abducent nerves were supplied by the anterolateral arteries (85.71%), and only some of them by the AICA (14.29%) or the pontomedullary artery (7.14%). The authors discuss the possible clinical significance of the anatomical data.

Transposition of the vertical rectus muscle to the insertion of a paralytic or aberrantly innervated lateral rectus muscle is useful in treating esotropia associated with abducens palsy and Duane syndrome. However, this procedure may cause a manifest vertical deviation, requiring either prismatic or additional surgical correction. In an attempt to reduce the incidence of this surgical complication, we performed vertical rectus muscle transposition surgery, using an adjustable suture technique on each muscle, in 10 consecutive patients with abnormal lateral rectus function. Preoperative diagnoses included abducens palsy (70%) and Duane syndrome (30%). Preoperative deviations ranged from 14 to 85 prism diopters esotropia (mean, 39 delta) in the primary position. No vertical deviation was present preoperatively. Following transposition surgery, 8 of 10 patients were esotropic, 1 of 10 patients was exotropic, and 4 of 10 patients had a manifest vertical deviation. At the time of adjustment, all vertical deviations were corrected by "recessing" the appropriate vertical rectus muscle. Additionally, exotropia was lessened by "recessing" both vertical muscles in one patient.

A single 5.5-millimeter to 8.0-millimeter lateral rectus resection eliminated diplopia in five of six adult patients with divergence paralysis and in all three patients with a sixth cranial nerve paresis. Preoperative distance esotropia ranged from 11 to 20 prism diopters in primary gaze. Prism therapy failed in seven of nine patients. Lateral incomitance was reduced in three patients with a mild limitation of abduction preoperatively, but was not induced in the six patients with divergence paralysis. Significant overcorrection of the near esodeviation did not occur. A single lateral rectus resection can effectively eliminate diplopia in selected patients with divergence and partial sixth nerve paralysis.

An acromegalic patient with pituitary apoplexy presented with multiple ocular nerve palsies with full visual fields. High resolution CT confirmed a pituitary tumour. We believe this clinical combination to be unique.

Sixteen reconstruction procedures of the third through sixth cranial nerves were carried out in 14 patients during operations on 149 tumors involving the cavernous sinus. A direct end-to-end anastomosis was performed in five nerves, whereas in 11 cases the nerve stumps were bridged by means of an interposing nerve graft. The sixth cranial nerve was most frequently reconstructed (nine cases). In four cases, the fifth nerve or root was repaired. The third nerve was reconstructed in two patients, and the fourth nerve was repaired in only one case. Recovery of function, either partial or complete, was observed in 13 nerves: the third in two instances, the fourth in one, the fifth in three, and the sixth in seven. No return of function occurred in three nerves. In patients with a successful recovery of cranial nerve function, either binocular function or the cosmetic result was improved. These results suggest that repair of the third through sixth cranial nerves injured during surgery should be pursued in suitable patients.

A ring-shaped electrode was developed and used in 20 patients to record evoked electromyographic responses directly from the extraocular muscles during skull base surgery. Intra-operative monitoring with this electrode helps the surgeon to localize the nerves that innervate the extraocular muscles precisely and to refrain from disturbing important neural structures during operations. Such monitoring also provides some insight into the pathophysiology of the dysfunction of these nerves resulting from skull base lesions.

Two cases of sixth cranial nerve schwannoma are presented with a review of four other cases from the literature. The clinical spectrum, neuroradiological findings, and surgical outcome of the six cases are discussed. There are two distinct clinical presentations for sixth cranial nerve schwannomas. Type I sixth nerve schwannomas present with sixth nerve palsy and diplopia and arise from the cavernous sinus. In contrast, type II sixth nerve schwannomas have a more severe presentation with obstructive hydrocephalus, raised intracranial pressure, sixth nerve palsy, and diplopia. This type arises along the course of the sixth cranial nerve in the prepontine area. Cavernous sinus involvement in either type may preclude total surgical excision and indicate an increase possibility for recurrence.

The case of a 3-year-old female is reported whose condition was diagnosed as congenital, complete paralysis of the right facial nerve in 1962; and a short time later more specifically described as Moebius syndrome. In 1971, a circumoral fascial sling was inserted in preparation for a masseter muscle transfer. Voluntary movement on the right side of her mouth was noted following surgery and continued to improve, making facial actions more symmetrical. This function has remained stable during a five year follow-up. Although the mechanism of action is not fully understood, it is postulated that the presence of the sling may have presented the subclinically active muscles a force to work against or perhaps the surgery may have liberated those muscles from adjacent fibrous tissue.