Retrosigmoid intradural suprameatal approach to Meckel's cave and the middle fossa: surgical technique and outcome

OBJECT: The goal of this study was to determine whether some petroclival tumors can be safely and efficiently treated using a modified retrosigmoid petrosal approach that is called the retrosigmoid intradural suprameatal approach (RISA). METHODS: The RISA was introduced in 1983, and since that time 12 patients harboring petroclival meningiomas have been treated using this technique. The RISA includes a retrosigmoid craniotomy and drilling of the suprameatus petrous bone, which is located above and anterior to the internal auditory meatus, thus providing access to Meckel's cave and the middle fossa. Radical tumor resection (Simpson Grade I or II) was achieved in nine (75%) of the 12 patients. Two patients underwent subtotal resection (Simpson Grade III). and one patient underwent complete resection of tumor at the posterior fossa with subtotal resection at the middle fossa. There were no deaths or severe complications in this series; all patients did well postoperatively, being independent at the time of their last follow-up examinations (mean 5.6 years). Neurological deficits included facial paresis in one patient and worsening of hearing in two patients. CONCLUSIONS: The approach described here is a useful modification of the retrosigmoid approach, which allows resection of large petroclival tumors without the need for supratentorial craniotomies. Although technically meticulous, this approach is not time-consuming; it is safe and can produce good results. This is the first report on the use of this approach for petroclival meningiomas.     

Microsurgical anatomy of the superior petrosal venous complex: new classifications and implications for subtemporal transtentorial and retrosigmoid suprameatal approaches

OBJECT: The purpose of this study was to define the patterns of drainage of the superior petrosal venous complex (SPVC) along the petrous ridge in relation to the Meckel cave and internal acoustic meatus (IAM) and to delineate its effect on the surgical exposures obtained in subtemporal transtentorial and retrosigmoid suprameatal approaches. METHODS: The patterns of drainage of the SPVC along the petrous ridge were characterized according to their relation to the Meckel cave and the IAM based on an examination of 30 hemispheres. Subtemporal transtentorial and retrosigmoid suprameatal approaches were performed in three additional cadavers to demonstrate the effect of the drainage pattern on the surgical exposures. CONCLUSIONS: The SPVC emptied into the superior petrosal sinus (SPS) within a distance of 1 cm from the midpoint of the Meckel cave. The patterns of drainage of the SPVC were classified into three groups. Type I emptied into the SPS above and lateral to the boundaries of the IAM. The most common type, Type II, emptied between the lateral limit of the trigeminal nerve at the Meckel cave and the medial limit of the facial nerve at the IAM, within an area of approximately 13 mm. Type III emptied into the SPS above or medial to the Meckel cave. The ideal SPVC for a subtemporal transtentorial approach (with or without anterior extradural petrosectomy) seems to be a Type I. In SPVC Type III and those Type II cases in which the SPVC is located near the Meckel cave, the amount of working space is significantly limited in a subtemporal transtentorial approach. In contrast, the ideal type of SPVC for a retrosigmoid suprameatal approach would be a Type III, and the SPVC must be divided in the majority of Type I and II cases for a satisfactory surgical exposure along the Meckel cave and middle fossa dura. The proposed modified classification system and its effect on the surgical exposure may aid in planning the approach directed along the petrous apex and may reduce the probability of venous complications.     

Lateral Suboccipital Retrosigmoid Approach with Tentorial Incision for Petroclival Meningiomas: Technical Note

Introduction The resection of petroclival meningiomas presents great neurosurgical challenges. Although multiple surgical approaches have been developed, the retrosigmoid route tends to be used to address tumors that are predominantly located in the posterior fossa. Our modification of the lateral suboccipital retrosigmoid approach with the placement of a tentorial incision yields good visualization of the supratentorial part of the tumor around the midbrain. Methods We treated four patients, one with primary and three with recurrent petroclival meningioma, by our modified approach. After lateral suboccipital craniotomy, the infratentorial part of the tumor was removed after detaching it from the tentorial surface. The cerebellar tentorium was then carefully incised from the supracerebellar angle, taking care not to damage the superior cerebellar artery and trochlear nerve. Results The operative field surrounding the midbrain was widened by this procedure, and safe dissection of the tumor from the brainstem and other neurovascular structures was performed with direct observation of the interface. Conclusions Our approach is a useful modification of the retrosigmoid approach to petroclival meningiomas. It facilitates the safe resection of the supratentorial part of the tumor in the ambient cistern behind the tentorium.     

Anatomical variation of superior petrosal vein and its management during surgery for cerebellopontine angle meningiomas

No systematic study is yet available that focuses on the surgical anatomy of the superior petrosal vein and its significance during surgery for cerebellopontine angle meningiomas. The aim of the present study was to examine the variation of the superior petrosal vein via the retrosigmoid suboccipital approach in relation to the tumor attachment of cerebellopontine angle meningiomas as well as postoperative complications related to venous occlusion. Forty-three patients with cerebellopontine angle meningiomas were analyzed retrospectively. Based on the operative findings, the tumors were classified into four subtypes: the petroclival type, tentorial type, anterior petrous type, and posterior petrous type. According to a previous anatomical report, the superior petrosal veins were divided into three groups: Type I which emptied into the superior petrosal sinus above and lateral to the internal acoustic meatus, Type II which emptied between the lateral limit of the trigeminal nerve at Meckel’s cave and the medial limit of the facial nerve at the internal acoustic meatus, and Type III which emptied into the superior petrosal sinus above and medial to Meckel’s cave. In both the petroclival and anterior petrous types, the most common vein was Type III which is the ideal vein for a retrosigmoid approach. In contrast, the Type II vein which is at high risk of being sacrificed during a suprameatal approach procedure was most frequent in posterior petrous type, in which the superior petrosal vein was not largely an obstacle. Intraoperative sacrificing of veins was associated with a significantly higher rate of venous-related phenomena, while venous complications occurred even in cases where the superior petrosal vein was absent or compressed by the tumor. The variation in the superior petrosal vein appeared to differ among the tumor attachment subtypes, which could permit a satisfactory surgical exposure without dividing the superior petrosal vein. In cases where the superior petrosal vein was previously occluded, other bridging veins could correspond with implications for the crucial venous drainage system, and should thus be identified and protected whenever possible.     

Two step approach for surgical removal of petroclival meningiomas with large supratentorial extension

The treatment of petroclival meningiomas is still a matter of controversy in literature. In the last decades, many approaches have been introduced. Our strategy for the treatment of such tumors having large supratentorial extension with encasement of the internal carotid artery or compression of optic and oculomotor nerves has evolved in the attempt to improve the outcome. Currently, we favor a surgical technique consisting of two steps. As first step, we perform a retrosigmoid suprameatal approach in order to resect the posterior part of the tumor and obtain brainstem decompression. In the second step, carried out after patient’s recovery from the first surgery, we remove the supratentorial portion of the lesion using a frontotemporal craniotomy to achieve the decompression of the optic nerve, oculomotor nerve, and carotid artery. The retrosigmoid suprameatal approach allows for adequate brainstem decompression: the tumor itself creates a surgical channel increasing the accessibility to the lower and upper petroclival surface. Moreover, this route allows for early visualization of cranial nerves in the posterior fossa and safe tumor removal under direct visual control, reducing the risk of postoperative deficits. Via the simple and safe frontotemporal craniotomy, the supratentorial part of the lesion can be removed thus avoiding the need of invasive approaches. We propose a two-stage surgery for treatment of petroclival meningiomas combining two simple routes such as retrosigmoid suprameatal and frontotemporal craniotomy. This approach reflects our philosophy to use simple and less invasive approaches in order to preserve neurological function and a good quality of life of the patient.     

Endoscopic approach-routes in the posterior fossa cisterns through the retrosigmoid keyhole craniotomy: an anatomical study

Endoscopy in cerebellopontine angle surgery is an increasingly used technique. Despite of its advantages, the shortcomings arising from the complex anatomy of the posterior fossa are still preventing its widespread use. To overcome these drawbacks, the goal of this study was to define the anatomy of different endoscopic approaches through the retrosigmoid craniotomy and their limitations by surgical windows. Anatomical dissections were performed on 25 fresh human cadavers to describe the main approach-routes. Surgical windows are spaces surrounded by neurovascular structures acting as a natural frame and providing access to deeper structures. The approach-routes are trajectories starting at the craniotomy and pointing to the lesion, passing through certain windows. Twelve different windows could be identified along four endoscopic approach-routes. The superior route provides access to the structures of the upper pons, lower mesencephalon, and the upper neurovascular complex through the suprameatal, superior cerebellar, and infratrigeminal windows. The supratentorial route leads to the basilar tip and some of the suprasellar structures via the ipsi- and contralateral oculomotor and dorsum sellae windows. The central endoscopic route provides access to the middle pons and the middle neurovascular complex through the inframeatal, AICA, and basilar windows. The inferior endoscopic route is the pathway to the medulla oblongata and the lower neurovascular complex through the accessory, hypoglossal, and foramen magnum windows. The anatomy and limitations of each surgical windows were described in detail. These informations are essential for safe application of endoscopy in posterior fossa surgery through the retrosigmoid approach.     

Removal of cavernous malformation of the Meckel's cave by extradural pterional approach using Heros muscle dissection technique

Background

We report on a patient with trigeminal neuralgia caused by an extraaxial cavernous malformation (CM) located within Meckel's cave. The lesion was removed via a pterional extradural approach with a modified temporalis muscle dissection technique, which was first described by Heros and Lee. Cadaveric dissections were performed to demonstrate the wider exposure gained by this approach.

Methods

A 56-year-old man presented with a history of episodic shocklike, right-sided facial pain for 10 years. Neurologic examination revealed diminished sensation in the mandibular division of the right trigeminal nerve. Magnetic resonance imaging showed an ipsilateral enhancing lesion in Meckel's cave.

Results

After placement of a lumbar drain, a right extradural pterional approach was undertaken. By reflecting the temporalis muscle posterolaterally, the craniotomy was extended so that the line of sight was level with the floor of the middle fossa. This allowed access to the lesion without needing to remove the zygoma. The lesion was resected with microsurgical technique. The patient's pain improved significantly after resection, and histopathologic examination confirmed the diagnosis of CM.

Conclusions

Extraaxial middle fossa CMs arising solely from Meckel's cave are rare. These lesions are safely and simply approached by posteriorly deflecting the temporalis muscle during a pterional craniotomy, avoiding excessive elevation of the anterior temporal lobe or further bony removal.     

乙状窦后锁孔入路对颅中后窝区的显微解剖

目的 研究乙状窦后锁孔入路对颅中后窝岩斜区结构的显微解剖,为临床应用该入路解决颅中后窝岩斜区病变提供解剖学依据. 方法 应用福尔马林固定的成人湿性头颅标本10例20侧,模拟乙状窦后锁孔入路对颅中后窝岩斜区进行显微解剖观察. 结果 乙状窦后锁孔入路从后外侧到达颅中后窝岩斜区,可以清楚暴露小脑半球外侧面、颞骨岩部、三叉神经、面听神经、部分后组脑神经、脑桥外侧面、椎动脉、小脑前下动脉.磨除部分岩骨可以扩大内听道及三叉神经的暴露,切开小脑幕缘可以暴露部分滑车神经及部分颅中后窝. 结论 乙状窦后经内听道上锁孔入路充分利用了有效的骨窗,手术创伤小、并发症少.该入路使少数原本需要采用复杂入路方能切除的颅中后窝肿瘤,可通过较简单的手术入路进行切除.对于主体位于颅后窝的岩斜区中小型肿瘤显微切除是一种有效、安全、便捷的微创手术方法.     

Locating the Internal Auditory Canal during the Middle Fossa Approach: An Alternative Technique

Options for the surgical exposure of the internal auditory canal (IAC) include the translabyrinthine, retrosigmoid, and middle fossa approaches. Of the three, the anatomical reference points to the IAC are most subtle when it is exposed from above. The classically described methods for localizing the canal during the middle fossa approach direct the surgeon's attention initially towards the lateral extremity of the canal, a location where the margin for error is at its minimum. The cochlea, semicircular canals, and geniculate ganglion of the facial nerve are all positioned in close proximity to the fundus of the canal. An approach which is initially directed towards the porus acusticus has the advantage of locating the canal away from these vulnerable structures in an area where there is a relatively wide margin of safety. In this medially directed technique, drill excavation is commenced in the petrous apex well anterior to the anticipated location of the porus. Once the medial portion of the IAC has been well defined, dissection can proceed laterally by removal of bone directly over the known course of the canal. This strategy minimizes the risk of injury to the viscera of the petrous bone.     

The middle fossa transpetrous approach for petroclival meningiomas

Seventeen patients with petroclival meningioma were operated on through a middle fossa transpetrous approach. This approach exposes the anterior cerebellopontine angle through a middle fossa craniotomy with removal of the petrous apex medial to the cochlea and petrous carotid artery. This approach may be enlarged by transection of the superior petrosal sinus and tentorium. The surgical technique and application of the middle fossa transpetrous approach for petroclival meningiomas is presented.     

The Middle Fossa Transpetrous Approach for Petroclival Meningiomas

Seventeen patients with petroclival meningioma were operated on through a middle fossa transpetrous approach. This approach exposes the anterior cerebellopontine angle through a middle fossa craniotomy with removal of the petrous apex medial to the cochlea and petrous carotid artery. This approach may be enlarged by transection of the superior petrosal sinus and tentorium. The surgical technique and application of the middle fossa transpetrous approach for petroclival meningiomas is presented.     

Endoscope-assisted microsurgical resection of epidermoid tumors of the cerebellopontine angle

OBJECT: Epidermoid tumors located in the cerebellopontine angle (CPA) are challenging lesions because they grow along the subarachnoid spaces around delicate neurovascular structures and often extend into the middle cranial fossa. The purpose of this study was to determine the value of endoscopic assistance in the microsurgical resection of these lesions, in which total removal is the therapy of choice. METHODS: Eight patients harboring an epidermoid tumor of the CPA were treated using an endoscope-assisted microsurgical technique. A retrosigmoid suboccipital approach was used in five patients and a pterional transsylvian approach was chosen in the other three. In four patients the lesion was resected microsurgically and the endoscope was used repeatedly to verify complete tumor removal, whereas most of the tumor mass was removed with the aid of an operating microscope in the other four. Tumor parts extending into other cranial compartments that were not visible through the microscope were removed under endoscopic view by using rigid rod-lens scopes with 30 and 70 degrees angles of view. All epidermoids were completely evacuated and the membranes were widely resected. Large tumors occupying both the middle and posterior cranial fossa were removed through a single small opening without enlarging the craniotomy. Permanent hearing loss and permanent hypacusis were observed in one patient each. One patient with facial and one with abducent nerve palsy recovered within 6 and 4 months, respectively. A transient weakness of the chewing muscles was encountered in one patient. Postoperative magnetic resonance imaging revealed no residual tumor in any patient. To date no recurrences have been-observed (follow up range 12-98 months). CONCLUSIONS: The endoscope-assisted microsurgical technique enables safe removal even when tumor parts are not visible in a straight line. Tumor extensions into adjacent cranial compartments can be removed with the same approach without retracting neurovascular structures or enlarging the craniotomy.     

The extended retrosigmoid approach for neoplastic lesions in the posterior fossa: technique modification

Approaches to the cerebellar-pontine angle and petroclival region can be challenging due to intervening eloquent neurovascular structures and cerebellar retraction required to view this anatomic compartment with the standard retrosigmoid technique. As previously described [11], the extended retrosigmoid provides additional access to space ventral to the brainstem through mobilization of the sigmoid sinus. We report our further experience and modifications of this approach for neoplastic pathology. The standard craniotomy is utilized, and the burr holes are placed slightly beyond the transverse sinus as well as the transverse–sigmoid junction and down towards the foramen magnum, as low as possible. Another burr hole is placed over the cerebral hemisphere to facilitate the dural dissection below the bone flap and over the transverse and sigmoid sinuses. We then perform a standard retrosigmoid craniotomy with a craniotome and the transverse and sigmoid sinuses are skeletonized. Consequently, the sigmoid sinus can then mobilized anteriorly to provide an unobstructed view in line with the petrous bone, while exposure of the transverse sinus provides access to the tentorium. Fifteen patients (March 2006–July 2008) underwent this approach to manage neoplastic lesions, including five meningiomas, three schwannomas, one epidermoid, and four intra-axial metastatic lesions. The nine extra-axial lesions were predominantly in the cerebellar-pontine angle with extension medial to the seventh/eighth nerve complex to the petroclival region. Gross total resection was obtained in all patients. The primary complication due to the exposure was a clinically asymptomatic sigmoid sinus thrombosis in one patient. Requiring a fundamental change in the management of the venous sinuses, the extended retrosigmoid craniotomy permits mobilization of the sigmoid and transverse sinuses. In this process, the entire cerebellar-pontine angle extending from the tentorium to the foramen magnum can be visualized with minimal cerebellar retraction. This technical modification over the standard retrosigmoid approach may provide a useful advantage to neurosurgeons dealing with these complex lesions.     

Arachnoid cysts of the posterior fossa

BACKGROUND: The surgical indications and management of posterior fossa arachnoid cysts (AC) are still controversial. Different surgical techniques and management have already been suggested for arachnoid cysts of the posterior fossa. AC involving the posterior fossa and especially the cerebellopontine angle may carry a high surgical morbidity because of the involvement of important neurovascular structures (e.g., brain stem and cranial nerves). Only long-term follow-up will determine the best surgical technique for such lesions. METHODS: Between 1990 and 1996 a total of 12 patients underwent surgery for arachnoid cysts involving the posterior fossa. In seven cases AC were located within the cerebellopontine angle (CPA), in three cases in the CPA with major extension dorsal to the brainstem, and in two cases at the CPA extending into the internal auditory canal. RESULTS: A suboccipital retrosigmoid approach was performed in all patients. Radical resection of the cyst could be accomplished in all but one case. There was no mortality. Major postoperative morbidity was present in one case because of an intraoperative air embolism in the semisitting position and strong adherence of the cyst wall to the surrounding neurovascular structures. Long-term follow-up (mean, 3.3 years) revealed improvement of most preoperative symptoms. CONCLUSION: Open surgery and radical removal of the AC located at the posterior fossa, based on our retrospective analysis, provide very good long-term postoperative results. The suboccipital approach provides a good and safe exposure of vascular structures and cranial nerves in the CPA and allows radical resection of the cyst, reducing the chance of recurrence.     

Meningiomas of Meckel's cave.

A series of 16 patients with meningiomas of Meckel's cave is reported. Trigeminal neuralgia, typical or atypical, was the initial symptom in 10 patients (62.5%). At admission, trigeminal signs and symptoms were present in 15 patients (93.7%); in 7 patients (43.7%), trigeminal dysfunction was combined with the impairment of other cranial nerves. On retrospective analysis, these patients fall into two clinical groups that differ also in prognosis. Group 1 comprises eight patients with trigeminal signs and symptoms only. These patients had small meningiomas strictly affecting Meckel's cave. Total removal of the tumor was achieved in seven of eight patients, without adjunctive postoperative neurological deficits. In this group, there were no tumor recurrences. Group 2 comprises the other eight patients in whom trigeminal dysfunction was combined with impairment of other cranial nerves. These patients had large tumors arising from Meckel's cave and secondarily invading the cavernous sinus (five patients) or extending into the posterior fossa (two patients) or largely growing into the middle fossa (one patient). Total removal was achieved in only one patient, and a worsening of the preoperative neurological status was observed in four patients; there were three cases of tumor progression. A subtemporal intradural approach (used in the past in every case) is still used for the small tumors of Group 1 with good results. Since 1985, for tumors involving the cavernous sinus, we have employed a frontotemporal craniotomy with extradural clinoidectomy and superior and lateral approach to the cavernous sinus. When the tumor extends toward the posterior fossa, we use a combined temporosuboccipital-transpetrosal approach.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cavernous hemangioma of Meckel's cave. Case report

A case of a cavernous hemangioma located within Meckel's cave and involving the gasserian ganglion is described in a patient presenting with facial pain and a trigeminal nerve deficit. Although these lesions have been reported to occur in the middle fossa, this is believed to be the first case of such a vascular malformation arising solely from within Meckel's cave.     

Primary malignant lymphoma of the trigeminal region treated with rapid infusion of high-dose MTX and radiation: case report and review of the literature

BACKGROUND: Extra-axial primary CNS lymphoma, considered rare, mainly arise in the white matter of the brain. Though the tumor responds well to radiation and chemotherapy, the prognosis of primary CNS lymphoma remains poor. We report a case of primary lymphoma of Meckel's cave mimicking a trigeminal schwannoma radiographically, which achieved complete remission through use of rapid high-dose MTX therapy and radiation therapy. CASE DESCRIPTION: The patient, a 55-year-old Japanese male, presented left trigeminal neuralgia. Magnetic resonance imaging (MRI) revealed a mass lesion in the left side of Meckel's cave, with extension into the cerebellopontine angle and the infratemporal fossa through the foramen ovale, suggesting trigeminal schwannoma. However, the patient suffered radiologically inexplicable progressive cranial nerve palsy, which suggested malignant disease. MRI and CSF disclosed malignant tumor dissemination; biopsy revealed malignant lymphoma. The treatment, composed of the rapid infusion of high-dose MTX and whole brain and spine radiation, resulted in complete remission. CONCLUSIONS: This case, which included atypical presentation of malignant lymphoma, illustrates the importance of including malignant lymphoma in the differential diagnosis of CP-angle and Meckel's cave tumor. The results also confirmed the usefulness of combined rapid high-dose MTX therapy and radiation.     

Multifocal choroid plexus papillomas: case report

Choroid plexus papillomas (CPP) are rare tumors of the central nervous system, usually occurring in the ventricular system. Apart from spinal drop metastases, CPPs are generally unique tumors. In this report, the authors present two exceptional adult cases involving multiple benign CPPs located in both intra- and extraventricular locations. The tumors were located in the fourth ventricle and Meckel's cave in one case and the cerebellopontine angle, the frontotemporal region and the fourth ventricle in the other. A review of the literature revealed that these two cases represent the first reported occurrences of multiple choroid plexus papillomas involving Meckel's cave and frontotemporal intraparenchymal locations.     

Clinicopathological study of meningiomas of the tentorium and its surrounding structures

We report the clinical features, radiological studies, operative procedures and results, and follow-up data in 29 patients with meningiomas of the tentorium and its surrounding structures. The cases represented 22.5% of all the intracranial meningiomas operated on in a 15 year period and were divided into three groups, depending on their main attachments, tentorial, cerebellopontine angle (dorsal aspect of the petrous ridge) and others. Tumor size was generally large and 13 cases were larger than 5 cm. The most common tumor site was along or near the superior petrosal sinus and transverse-sigmoid junction in cases involving the tentorium, and medial to the porus acousticus in cases involving the cerebellopontine angle. Different operative approaches to these tumors were carried out, depending on their location. The tumors in the lateral or medial petrous ridge were approached mainly with a suboccipital craniectomy using a retromastoid incision. Total removal was carried out in 80% of the tentorial cases, in 46.2% of cerebellopontine angle cases, and in the 83.3% in the others. Total operative mortality rate was zero. Follow-up periods ranged up to 5 years 5 months in the tentorial cases, 4 years 6 months in cerebellopontine angle cases, and 7 years 1 month in the others. Long-term results were good in 21 cases (72.4%), fair in 3 cases (10.3%) and poor in 2 (6.9%). Three patients died due to tumor recurrence. One of them suffered lung metastasis, and two of them suffered extensive local recurrences. We recommend the retromastoid approach combined with the petrosal approach, if the CPA tumor is large enough and extends to the retroclival region.