Suboccipital Retrosigmoid Approach Research Articles

Dumbbell-Shaped Hypoglossal Schwannoma Removed via Retrosigmoid Suboccipital Approach

Introduction: Dumbbell-shaped schwannomas of the hypoglossal nerve are very rare. In general, a far lateral or transcondylar approach may be applied to hypoglossal schwannomas lying mainly in the posterior fossa to reach the hypoglossal canal. We report a case of dumbbell-shaped hypoglossal schwannoma resected via the retrosigmoid suboccipital approach.

Ventral petrous meningiomas: unique tumors

Introduction This study aims to analyze our experience with petrous meningiomas (PM), testing the hypothesis that these tumors have different histologic subtypes and operative outcome depending on the site of origin in reference to the internal auditory canal (IAC). Methods Fifty-eight patients with PM were reviewed retrospectively. Tumors were classified as posterior (PPM; n = 29), superior (SPM; n = 8), and ventral petrous (VPM; n = 19), in reference to the IAC. Two patients had multiple meningiomas arising from different parts of the petrous bone. Petroclival, clival, and jugular tubercle meningiomas were excluded. All patients were operated through a suboccipital retrosigmoid approach. Clinical presentation, tumor size, involvement of IAC, extent of resection, outcome, and tumor histology were analyzed. Results Simpson grade I and II resection was achieved in 84.5%: 96.6% in PPM, 100% in SPM, and 57.9% in VPM. Fibrous histology accounted for 69% in PPM, 62% in SPM, and only 10.5% in VPM, whereas meningothelial histology was seen 27.6%, 25%, and 68.4%, respectively. Postoperative hearing loss was the most frequent operative complication, and was seen in 31.6% of VPM, as compared to none in PPM or SPM. Conclusions Ventral petrous meningiomas are clearly different tumors in their histology and operative outcome. The predominance of meningothelial histology in this location may imply a different tumorigenesis as compared to other PM. Ventral petrous meningiomas should be viewed as a distinct group of tumors.

A new method of patient′s head positioning in suboccipital retrosigmoid approach

The retrosigmoid approach is a common route to the cerebellopontine angle and lateral clivus. Patient's head positioning just before the operation is crucial to perform the procedure effectively and safely. The aim of the study is to determine the positional angle of the head on preoperative axial sequences of the cranial magnetic resonance imaging (MRI). The angle between the line drawn along the petrous bone ventral to the internal auditory canal and the line drawn parallel to the dorsal face of the clivus on the axial view of MRI sequences was measured. This method of patient positioning has resulted in minimal cerebellar retraction, less time in the preoperative preparation period and less postoperative headache and neck pain. This method can provide quick and better exposure of the cerebellopontine angle. Preoperative measurement of positional angle on axial MRI sequences is a very simple and sufficient way to determine the angle of the head that is turned to the contralateral side.

Microsurgical treatment for tumors in jugular foramen and its around

Objective To explore the micresurgical techniques and outcome of tumors in jugular foramen and its around. Methods Eleven patients with jugular foramen tumors were operated through suboccipital-retrosigmoid approach (2 cases), jugular foramen approach (2 cases), temporal fossa approach (4 cases) and mastoid-cervical combined approach (3 cases). Results Nine tumors were totally removed and 2 were subtotally removed. Of those cases, there were 4 neurinoma, 4 paragangliome, I meningioma, 1 mucochondrosarcoma, and 1 low-differentiated carcinoma. Postoperative complications included transient cerebrespinal fluid leak(1 case) and new lower cranial nerve injury (2 cases). All cases were followed up for mere than 8 months. The postoperative hearing was improved in 1 case, stable in 6 cases, deteriorated in 4 cases. Postoperative facial paralysis of grade Ⅱ- Ⅲ occurred in 3 of 9 patients without facial paralysis, which recovered in half a year. Of 2 patients with facial paralysis before surgery, facial function was improved in 1 case and stable in 1 case. Conclusion Proper surgical approaches and micrceurgical techniques, which were adopted according to the types, the location, and the expansion of tumors, the function of facial nerve and lower cranial nerves, and hearing level, are good for reducing complications, exposing and removing jugular foramen tumors. Key words: Jugular foramen; Skull base tumor; Micresurgery

Pediatric primary pilocytic astrocytoma of the cerebellopontine angle: a case report

We describe a rare case of pediatric pilocytic astrocytoma presented as a right cerebellopontine angle (CPA) mass, completely separated from the brain stem and arising from the proximal VIII nerve portion. A 12-year-old boy, with no evidence of neurofibromatosis type 2, presented with progressive hearing loss at the right ear and headache. An initial enhanced magnetic resonance examination suggested the diagnosis of schwannoma. The tumor was resected by a suboccipital retrosigmoid approach. Our case seems to be the first report of a primary pediatric CPA pylocitic astrocytoma arising from the VIII nerve complex and presenting internal auditory canal enlargement. It represents the third reported case of a primary CPA pilocytic astrocytoma (the second pediatric case with the first arising from V nerve) and the eighth report of primary CPA glioma, overall. We discuss the clinical, neuroradiological, and intraoperative findings, and we review the different hypothesis about the origin of these rare tumors.

SURGERY OF EXTRA-AXIAL TUMORS OF THE CEREBRAL BASE

Because of the complex structure of the cranial base and its close proximity to cranial nerves and vessels, surgery in this area is associated with considerable risk of morbidity and mortality. Multiple approaches to each part of the cranial base have been developed over the past few decades, ranging from small modifications of more traditional approaches to complex and sophisticated new techniques. However, experience has shown that optimal outcome is achieved if the selected approach is not associated with significant approach-related morbidity. Furthermore, not all cranial base tumors can be cured by surgery. The selection of operative approach and the goal of surgery should be part of the whole treatment strategy. The attempt to achieve complete resection can, therefore, be justified only if the associated long-term morbidity is minimal. Refinements of the traditional retrosigmoid suboccipital approach have made it the most effective and safe approach, the "gold standard" for lesions in the cerebellopontine angle. On the other hand, in some basal tumors, e.g., chordomas and chondrosarcomas, the approach has to be selected individually and must always be tailored to the characteristics of the particular tumor, its location, and the patient's expectations. The expertise of the surgeon is not reflected in his or her ability to perform the most complex approaches but in the ability to select the approach that affords both removal of the tumor and preservation of patient's neurological function and quality of life.

Prevention of facial nerve injury in acoustic neuroma microsurgery

To summarize and analyse the techniques of avoiding facial nerve injury during acoustic neuroma microsurgery. One hundred and eighty patients with large acoustic neuroma (> or =4 cm) and 70 patients with medium acoustic neuroma (2.4-4.0 cm) were diagnosed by MRI/ CT scan before operation and confirmed by postoperative pathologic examination. All of patients were treated by sub-occipital retrosigmoid approach for tumor removal and facial nerve reservation during operation. The relationships among the bone, arachnoid, nerve and vascular anatomy were particularly observed during the operation. After decompression of the tumor, the origination and location of the facial nerve as well as the relationship between the tumor and the facial nerve should be identified. The patients were followed-up from 6 months to 1 year postoperatively and assessed by House-Brackmann facial nerve function grading system. Total tumor resection was achieved in 240 of 250 cases (96%) and subtotal in 10 cases including 1 case died because of cerebellar encephalomalacia after operation. According to the House-Brackmann facial nerve function grading, recovery of normal function (grade I) was achieved in 214 cases (85.6%), grade II in 25 cases (10%), grade III in 5 cases (2.09%) and grade IV in 5 cases (2.09%). Microneurosurgical techniques are helpful for total resection of acoustic neuroma and keeping facial nerve anatomic intact.

Radiosurgery時代の大きな聴神経腫瘍に対する機能温存を考えた意図的部分摘出 : suboccipital retrosigmoid approach(手術手技・周術期管理)

Radiosurgery時代の大きな聴神経腫瘍に対する機能温存を考えた意図的部分摘出 : suboccipital retrosigmoid approach(手術手技・周術期管理)

Significance of the tentorial alignment in approaching the trigeminal nerve and the ventral petrous region through the suboccipital retrosigmoid technique

In this study, the authors aimed to identify the factors that would predict the operative distance between the trigeminal nerve (fifth cranial nerve) and the acousticofacial nerve complex (seventh-eighth cranial nerves) preoperatively when approaching the cerebellopontine angle (CPA) through the suboccipital retrosigmoid approach. In 40 consecutive patients who underwent microvascular decompression of the trigeminal nerve via a suboccipital retrosigmoid approach for trigeminal neuralgia, the following three parameters were assessed on preoperative magnetic resonance images: 1) the angle between the tentorium and the line drawn from the hard palate (tentorial angle); 2) the angle between the lines drawn along the petrous bones ventral to the internal auditory canals (petrous angle); and 3) the angle between the tentorium and the line connecting the opisthion to the inion (occipital angle). The distance between the trigeminal nerve and the acousticofacial nerve complex (referred to as "distance") was measured intraoperatively. Statistical analysis was performed using the Pearson correlation test. The mean values were 50.9 +/- 11.5 degrees for the tentorial angle, 102.5 +/- 13.1 degrees for the petrous angle, 83.4 +/- 9.7 degrees for the occipital angle, and 3.1 +/- 1.5 mm for distance. There was a strong inverse correlation between the tentorial angle and distance (r = -0.228, p = 0.08). The mean distance was 3.5 +/- 1.9 mm for a tentorial angle less than 51 degrees and 2.7 +/- 1.1 mm for a tentorial angle of at least 51 degrees. No correlation existed between either the petrous or occipital angles and distance. The distance between the trigeminal nerve and acousticofacial nerve complex decreases in the presence of a steep tentorial angle. This limits the operating field between these cranial nerves when reaching the petroclival or the superior CPA regions through the retrosigmoid approach. Awareness of such anatomical features at the time of preoperative planning is of paramount importance in selecting the optimum surgical approach and minimizing operative complications.

Non-invasive acoustic neuroma treatment via Gamma Knife stereotactic radiosurgery

Non-invasive acoustic neuroma treatment via Gamma Knife stereotactic radiosurgery

Epidermoid cysts of the cerebellopontine angle with extension into the middle and anterior cranial fossae: surgical strategy and review of the literature

Epidermoid cysts are tumours, which contain keratin, cellular debris and cholesterol, and lined with stratified squamous epithelium. Clinically, epidermoid cysts behave like benign, slow-growing lesions. We present a 63 year-old man with a 6-month history of right periorbital pain and hypaesthesia in the area of the first and second branch of the trigeminal nerve. MRI revealed an epidermoid cyst of the cerebellopontine angle extending into the middle and anterior cranial fossae. Radical surgical removal of epidermoid cysts should be attempted, but a less aggressive surgical strategy should be considered if there is strong adherence to the surrounding brain tissue, particularly in eloquent areas. In this case, complete tumour removal was achieved via a suboccipital retrosigmoid approach.

Acute Intratumoral Bleeding in a Cystic Vestibular Schwannoma: Case Report

Introduction: Vestibular schwannomas are slow-growing tumors with progressive hearing and vestibular symptoms as the usual presentation. Cystic degeneration in schwannomas are found not so rarely, and it is probably secondary to microhemorrhages inside the tumor. We report a very unusual case of vestibular schwannoma with a massive hemorrhage inside the tumor and abrupt clinical presentation. Methods: We reviewed the cases of vestibular schwannomas treated by the authors with particular attention to their presentation symptoms and the occurrence of associated cysts. Results: We report a case of a 52-year-old female with acute presentation symptoms of intracranial hypertension and compression of the brain stem due to a large cystic vestibular schwannoma with massive bleeding inside the cyst. Total removal of the tumor was obtained through a suboccipital retrosigmoidal approach after the drainage of the hemorrhagic collection inside the tumor. Pathological studies confirmed hemosiderin deposition in the walls of the cyst. Conclusions: We report the CT and MR imaging appearance and the operative findings of a very rare case of massive intratumoral bleeding in a vestibular schwanoma. This unusual and unpredictable occurrence would be considered as an additional risk in the cases treated conservatively or with gamma-knife.

Significance of the Tentorial Alignment in Approaching the Trigeminal Nerve through the Suboccipital Retrosigmoid Technique

Introduction: In this study, we aimed at assessing the significance of the tentorial alignment in approaching the trigeminal nerve through a suboccipital retrosigmoid craniotomy. Methods: Four parameters were evaluated using preoperative MRI and intraoperative measurements in 34 consecutive patients who underwent microvascular decompression of the trigeminal nerve via a suboccipital retrosigmoid approach: (1) the angle between the tentorium and the line drawn from the hard palate (tentorial angle, TA); (2) the angle between the tentorium and the line connecting the opisthion to the inion (occipital angle, OA); (3) the angle between the lines drawn along the petrous bones ventral to the internal auditory canals (petrous angle, PA); (4) the intraoperative distance between the trigeminal nerve and the acousticofacial bundle (distance, d). Statistical analysis was performed using Pearson's correlation test and t-test as appropriate. Results: Mean values were 50.1 ± 12.2 for TA, 82.3 ± 9.9 for OA, 104.6 ± 12.2 for PA, and 3.2 ± 1.5 mm for d. There was a negative correlation between TA and d (r = − 0.233, p = 0.09): the mean d was 3.7 ± 1.7 mm for TA 51 (p = 0.06). A positive correlation was detected between TA and OA (r = 0.336, p = 0.02). Conclusions: The distance between the trigeminal nerve and the acousticofacial bundle decreases in the presence of a steep tentorial angle. This limits the working field at the petrotentorial sulcus. Awareness of such anatomical features at the time of preoperative planning is of paramount importance to avoid complications during the procedure.

PRESERVATION OF FUNCTION IN VESTIBULAR SCHWANNOMA SURGERY

The management and surgical technique for microsurgical tumor removal of vestibular schwannomas (acoustic neuroma) with the suboccipital retrosigmoid approach and semi-sitting patient positioning is described. An emphasis is placed on the preservation of auditory and facial nerve function with a stepwise description of the technical and operative nuances, including presurgical evaluation, positioning, anesthesiological and neurophysiological aspects, approach, microsurgical techniques, and postsurgical care.

Cavernous angiomas within the internal auditory canal

The aim of this study was to describe the symptomatology, radiological features, and surgical treatment of patients with cavernous angiomas within the internal auditory canal (IAC). The authors reviewed the cases of seven patients with cavernous angiomas in the IAC that had been surgically treated in the 22-year period between 1983 and 2005. All the patients had presented with sensorineural hearing loss, and four suffered from tinnitus. Four patients also reported facial symptoms such as hemispasm or progressive palsy; one of these patients had presented with sudden facial paresis due to intrameatal tumor hemorrhage. According to computed tomography (CT) results, the lesions caused enlargement of the IAC. Interestingly, these same angiomas showed variable features on magnetic resonance (MR) imaging, making their differentiation from intrameatal vestibular schwannomas (VSs) sometimes impossible. In all patients the lesions were totally removed via the suboccipital retrosigmoid approach. They could be dissected away from the facial nerve in five cases, whereas in two cases, because of the location of the lesion, the seventh cranial nerve had to be sectioned and repaired with a sural nerve graft. Transient worsening of seventh cranial nerve symptoms occurred in two patients, with postoperative improvement in each of them. The cochlear nerve could not be functionally preserved because of its extreme adherence to the tumor, although its continuity was preserved in four patients. Complete deafness was the only postoperative complication. Cavernous angiomas of the IAC are very uncommon lesions that can imitate the symptoms of VSs. Although it is the most sensitive study available, MR imaging does not show sufficiently specific findings to differentiate the two lesion types. Thus, the preoperative diagnosis must be based on patient symptoms plus the CT and MR imaging features.

Vascular complications of vestibular schwannoma surgery: a comparison of the suboccipital retrosigmoid and translabyrinthine approaches

Vascular complications of the surgery for vestibular schwannomas (VSs) can have devastating consequences; however, there is scant literature on the systematic analysis of the different types of complications. In this context, the authors of this study analyzed these complications, with particular interest in the role of surgical approach in their occurrence. The charts of 391 patients who had undergone 413 procedures for VS during a 24-year period were reviewed retrospectively. A suboccipital retrosigmoid (RS) approach was used in 338 procedures, and the translabyrinthine (TL) route in 75. Postoperative hemorrhage or infarction was identified and stratified according to the complication type and surgical approach. Postoperative vascular complications were encountered in 11 procedures (2.7%), and their incidence was the same for both the RS and TL approaches. Of these complications, eight were hemorrhagic (two cerebellopontine angle, one intracerebellar, and five epidural hematomas) and three were ischemic in nature. Five patients (45.4%) had a complete recovery, and four patients (36.4%) a partial recovery; two patients (18.2%) died. The overall procedure-related mortality rate was 0.5% (two of 413 procedures): 0.3% (one of 338 procedures) for the RS approach and 1.3% (one of 75 procedures) for the TL approach (p > 0.05). In this study, the overall incidences of vascular complications in VS surgery were similar for the RS and TL approaches. Regardless of the preferred surgical route, this group of complications carries a significant risk of morbidity and therefore warrants special consideration in the management of VSs.

Microsurgical Excision of the Large or Giant Cerebellopontine Angle Meningioma

The object of this study was to analyze the therapeutic effects of microsurgical excision in cases with the large or giant cerebellopontine angle meningioma. We retrospectively analyzed the 56 patients who suffered from the large or giant cerebellopontine angle meningioma and underwent the microsurgical therapy, for which the suboccipital-retrosigmoidal approach was adopted in 38 cases, the temporal-occipital craniotomy, presigmoidal approach in 6 cases, the temporal-occipital craniotomy, inferotemporal tentorium cerebelli approach in 8 cases, and the temporal-occipital craniotomy, supratentorial or infratentorial allied approach in 4 cases. The tumors of 44 cases were all resected (Simpson I, II), with a total resection rate of 78.6%, and there was no operative mortality. After surgery, symptoms improved in 40 cases and remained unchanged in 10 cases. Among 54 cases, recrudescence was seen in 2 cases (3.7%) and being able to take care of themselves in 50 cases (92.6%) at 6 months through 6 years follow-up after surgery. A rationally selected surgical approach, a microscopic technology applied in the operation to appropriately treat and protect vein, nerve and brain stem, which can ideally excise the tumors, together can increase the survival ability of patients.

Facial and Cochlear Nerve Function after Surgery of Cerebellopontine Angle Meningiomas

Meningiomas of the cerebellopontine angle (CPA) share a common location, but their site of dural origin and their relationship to surrounding neurovascular structures of the CPA are variable. The clinical presentation and outcome after surgical resection are different because of the diversity of this tumor entity. We report on a series of 421 patients with CPA meningiomas, with special emphasis on the analysis of the preoperative and postoperative facial and cochlear nerve function in relation to the site of dural attachment and main tumor location in the CPA cistern. Among 421 patients, the charts of 347 patients with complete clinical data, including the history and audiograms, imaging studies, surgical records, discharge letters, histological records, and follow-up records, were reviewed retrospectively. Data about preoperative and postoperative facial nerve function were available in 334 patients, and audiometric analysis was conducted in 333 patients. Patients with neurofibromatosis Type 2 were excluded from the study. There were 270 women and 77 men, with a mean age of 53.4 years (range, 17.6-84 yr). Among these patients, 32.9% of the tumors originated at the petrous ridge anterior to the inner auditory canal (IAC) (Group 1), 22.2% showed involvement of the IAC (Group 2), 20.2% were located superior to the IAC (Group 3), 11.8% were inferior to the IAC (Group 4), and 12.9% were posterior to the IAC, originating between the IAC and the sigmoid sinus (Group 5). Patients presented with disturbance of Cranial Nerves V-VIII, the lower cranial nerves, and ataxia, depending on the main tumor location. Tumor resection was performed through a suboccipital-retrosigmoidal approach in the semisitting position in 95% of the patients. A combined supratentorial-infratentorial presigmoidal approach was performed in 5%. Total tumor removal (Simpson Grade 1 and 2) was achieved in 85.9% and subtotal removal in 14.1%. The best initial postoperative facial and auditory nerve function was observed in tumors belonging to Groups 3 and 5. Recovery from preoperative deafness was observed in 1.8% of patients. On long-term follow-up, good facial nerve function (House-Brackmann Grade 1 or 2) was observed in 88.9% of patients. Hearing preservation among patients with preoperative functional hearing was documented in 90.8% on long-term follow-up. Although the outcome of facial and cochlear nerve function is different in CPA meningiomas, depending on the topographic classification of these tumors, preservation of the cochlear nerve is possible in every tumor group and should be attempted in every patient with CPA meningioma. It has to be kept in mind that recovery of hearing was also observed in patients with preoperative profound hearing deficits.

Microsurgical treatment jugular foramen tumors

目的 探讨颈静脉孔区肿瘤显微手术的临床疗效.方法分析近4年采用显微外科技术治疗颈静脉孔区肿瘤10例的临床资料,主要临床表现为听力下降和后组脑神经损害,术前行头颅核磁共振和颅底薄层CT扫描,8例行数字减影脑血管造影检查.采用显微外科手术切除,其中经颈静脉孔入路6例,远外侧入路2例,枕下乙状窦后入路2例.结果 10例术中肿瘤全切除9例,次全切除1例.病理学示神经鞘瘤6例,神经纤维瘤1例,脑膜瘤1例,转移瘤1例,颅咽管瘤1例.术后2例完全清醒后未及时行气管切开术而突发喉头水肿窒息死亡.存活8例磁共振复查显示肿瘤全切除7例,次全切除1例.8例术后症状改善3例,症状不变3例,症状加重2例.结论采用显微外科技术选择适当的手术入路可以较好地切除颈静脉孔区的肿瘤,经颈静脉孔入路可能是该区域肿瘤手术治疗的最佳入路。

Evaluation of the Results of Endoscope-Assisted Acoustic Neuroma Surgery through Posterior Fossa Approach

The objective of this study was to evaluate the results of endoscope-assisted acoustic neuroma surgery in posterior fossa approach. Between 1996 and 2002, 60 consecutive patients with acoustic neuroma were operated via the retrosigmoid suboccipital approach. Standard 4-mm sinus endoscopes at different angles were used during the surgeries either for inspection or tumor endoscopic dissection. Clinical parameters and treatment outcome were evaluated retrospectively. Tumor sizes were small, medium and large in 46.6, 45 and 8.3% of the patients, respectively. The hearing preservation rate, which did not correlate with tumor size (p > 0.05), was 24.4%. The need for facial reanimation surgery, which was needed in 5% of patients, was significantly higher in the large tumors than in the small and medium tumors (p < 0.001). Cerebrospinal fluid fistula rate, which was not related to tumor size (p > 0.05), was 13.3%. Tumor recurrence or residual tumor was not encountered at all. In conclusion, endoscopes give accurate information about the relationship between the tumor and the adjacent structures and help control the fundus of the internal auditory canal to ensure complete tumor removal. It is also helpful in visually verifying the continuity of the facial and cochlear nerves. The use of endoscopes does not appear to increase the hearing preservation rate, but is very helpful in complete tumor removal in the posterior fossa approach.