Treatment of petroclival meningiomas

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(reproduced in Professor Gu Jianwen's blog) at the confluence of the petroclival fissure petroclival region is located in the back of the pe

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(reproduced in Professor Gu Jianwen's blog) at the confluence of the petroclival fissure petroclival region is located in the back of the petrous bone and occipital slope, from the petrous apex to the jugular foramen. The medial lateral to the midline to the slope, V, VII and VIII cranial nerves on edge for the saddle back, under the edge of the jugular foramen; below the foramen magnum. Because of the location of the petroclival region, adjacent to the important anatomical structure, it is difficult to achieve complete resection of the tumor, and has a high rate of postoperative morbidity. In recent years, the improvement of microsurgical technique and the attempt and improvement of various skull base approaches have significantly improved the therapeutic effect. The present status and progress of treatment of petroclival meningiomas at home and abroad are summarized as follows. Intracranial meningioma is about 0.3% ~ 1% of the most common lesions in petroclival region. It is up to the invasion of petrous apex, tentorium, Meckel cavity, and parasellar cavernous sinus; downward invasion of internal auditory canal and jugular foramen; to the inside of the brainstem and vertebral basilar artery. When the tumor is large, can be wrapped around the ipsilateral cranial nerve III ~ xi. Clinical manifestations of headache, complex cerebral palsy, ataxia and other symptoms, severe cases of hemiplegia, cognitive dysfunction. Most of the petroclival meningiomas are benign, and surgical resection is the first choice.

Petroclival tumors in patients with preoperative evaluation is very important, the conventional MRI examination is helpful to understand the size of the lesion, and extent of invasion, relationship with surrounding structures, especially on brainstem edema, cerebral damage. By analyzing the correlation between tumor parenchyma and peritumoral edema in MRI perfusion imaging, it is helpful for the diagnosis of meningioma subtypes. Single photon emission computed tomography (SPECT) can be used to distinguish between benign and anaplastic meningioma, but also evaluate the proliferative potential. Preoperative DSA examination showed high blood flow meningioma, preoperative embolization can significantly reduce intraoperative bleeding, improve surgical safety and total resection rate, and the best operation time is 7 ~ 9d. Chernov et al. Study on the blood flow of the brain stem and cerebellum before operation. The results showed that the blood flow of the ipsilateral brain stem decreased significantly, and there was as much as 20% reduction in cerebellar blood flow. It is possible to reduce cerebral blood flow by direct compression, peritumoral edema, secretion of active metabolites, and direct wrapping of blood vessels. Results the patient was at high risk of neurological dysfunction and cerebellar ataxia. In the dominant hemisphere lateral skull base approach before surgery by DSA and MRV on Labbe 's vein, sigmoid sinus and jugular bulb development and whether the main side drainage to judge, can provide important reference for the safe operation of sigmoid sinus occlusion. It is necessary to evaluate the drainage of cavernous sinus by anterior approach. If is the main form of venous venous drainage of the cavernous sinus and inferior petrosal sinus dysplasia, epidural in surgical operation, may be blocking the superficial middle cerebral vein and basal vein via transsphenoidal cavernous sinus through venous drainage pathway of sphenoid guide to venous plexus, causing additional damage of temporal lobe. At this point, the surgeon should consider the posterior approach of the petrous bone, or the lateral suboccipital approach, or the removal of the petrous apex around the foramen ovale without epidural operation. In a study of 137 patients with petroclival meningioma study, patients with total resection of tumors was 40%, subtotal resection in 40%, it concluded that subtotal resection and not for those patients with tumor adhesion properties or fibrosis, significantly reduces the incidence of postoperative neurological dysfunction, and no increase in tumor recurrence the rate of. Li et al. Suggested that the tumor had a high risk of neurological dysfunction after wrapping the neurovascular structures or invading the cavernous sinus. The growth of meningiomas in the petroclival region is slow, and the patient can maintain a good neurological function. Therefore, incomplete resection should be considered as an acceptable treatment option. Surgical resection of large petroclival meningiomas with brain stem compression is an accepted treatment option. But the treatment for small petroclival meningioma is controversial, often have the following questions: (1) whether the tumor had symptoms; (2) the symptoms can be improved after the treatment of the tumor; (3) if the patients need treatment? If necessary, what time to start treatment; (4) wait and see strategy for the symptoms or asymptomatic cancer is appropriate; (5) if the lesion in MRI showed increased, whether it should be removed, even patients still asymptomatic; (6) follow the wait and see strategy, because of the small amount of cavernous sinus invasion or around the brain, vascular surgery, can become inoperable tumor; (7) in order to obtain base excision (Simpson I-II) and no injury of nerves and blood vessels, when is the best time of treatment; (8) what kind of treatment is the best choice without causing additional damage for benign tumor. Follow up observation showed that small petroclival meningiomas, especially in young patients, showed a high growth index (diameter: 0.106mm / month). The use of waiting and observation strategies may miss the optimal treatment of tumors at optimal time. Yamakami thinks that resection is the preferred method for the treatment of small petroclival meningiomas, can cure the disease and low morbidity; transpetrosal front is the most appropriate approach. Therefore, once patients with neurological symptoms or imaging to observe the tumor growth, it must be clear surgical treatment, to obtain satisfactory results.

surgical treatment

Microsurgical treatment of petroclival tumors began 20 years ago in the Department of Neurosurgery "N.N.Burrdenko", before 1990, a considerable number of patients have been benefited by surgery. According to the location of the tumor, the location of the center, the direction of expansion, the size of the patient, the age of the patient, the physiological state of the disease and the extent of the preoperative planning, different surgical approaches were used. The selection of surgical approach for petroclival meningiomas is made up of anterior petrous bone, posterior petrous bone, sigmoid sinus and combined approach.

The anterior approach of petrous bone (Kawase approach) is essentially an enlarged approach to the middle cranial fossa combined with anterior resection of the petrous bone. For lesions located in the upper slope and petroclival region, namely saddle back and above between the internal auditory canal. The approach of the seventh and eighth cranial nerve injury, rarely affected anatomic variation of the sigmoid sinus and the jugular bulb. But on the ventral side and the petroclival exposure, in order to improve exposure, can remove the zygomatic arch, the mandibular branch of the trigeminal nerve and the pre expanded removal of the middle fossa. Approach is required to maximize the removal of petrous apex without hearing damage, it is limited to the internal carotid artery and lateral cochlear. The 2.1mm thick bone (0.6 ~ 10.0mm) is separated from the cochlea and internal carotid artery, which is vulnerable to the injury of the internal carotid artery. Therefore, the precise localization of the cochlea is important for maximizing the removal of the anterior portion of the petrous bone. Seo through the thin slice CT scan for 70 of the petrous bone, pointed out in the cochlea of the petrous internal carotid artery after angle, preoperative measurement of cochlear depth, and the level of the petrous internal carotid artery after central extension of the distance between the line and turn basilar (the average distance is 0.6mm, from 4.9 to 3.9mm. No significant correlation with age and gender), safety area of rock prevertebral part grinding, save the operation time and increase the safety of guidance.

The posterior petrous bone in the upper slope is suitable for many types of tumors and vascular lesions, the preferred surgical transpetrous presigmoid approach Shiyan petroclival lesions. Including the labyrinth, part of the labyrinth, the labyrinth and the cochlea approach. Zhang Junting believes that this approach is the treatment of petroclival lesions best approach, its advantages: (1) the cerebellum, temporal lobe retraction slightly; (2) easy treatment of the tumor base, blocking tumor blood supply; (3) at the slope distance than other approaches to shorten 3cm; (4) multi angle straight ventral side; (5) the sigmoid sinus, Labbe 's vein is not affected. But its disadvantages are also very prominent, time-consuming, high infection rate, and the translabyrinthine approach of cochlear hearing loss, because of high jugular bulb, front sigmoid sinus, middle cranial fossa bone plate and the effects of low exposure, bone excision papilla formation formed easily lead to cerebrospinal fluid leakage, low cure rate and poor prognosis. Retrolabyrinthine approach is theoretically the most secure method, but the lack of exposure to the internal auditory canal area, operative angle of the upper petroclival region is poor, limiting its usefulness; some transcochlear approach provides much better exposure, can well protect the hearing and facial nerve function; translabyrinthine approach the road and the permanent damage of the cochlear hearing approach is 100%, the rear of the facial nerve in patients with almost all observed facial paralysis symptoms, only for hearing loss, lesions extending to the internal auditory canal or include petrous bone itself, and patients need to reach the petrous internal carotid artery. Wu et al., retrolabyrinthine approach provides (93.1 + 17.6) mm2 visual slope area, while some transcochlear approach provides (340.1 + 47.1) mm2, respectively, transcochlear approach (24.6 + 1.6)% and (90.3 + 2.3)%. Statistics showed that there was no significant difference between the labyrinth, the labyrinth and the cochlear approach when exposed to the slope. But the operation of freedom in the retrolabyrinthine approach and transcochlear approach, and transcochlear approach and transcochlear approach has obvious progress compared to the transcochlear approach were (60.3 + 5)% and (77.7 + 5.3)% and (93.6 + 2.1)%. Mandelli part of the translabyrinthine approach provides exposure to the ventral surface of the pons part 122mm2, transcochlear approach and post facial nerve provides 170mm2 exposure, and this increase in the exposed area of the cost of hearing loss and facial nerve injury; the former can save about 90% of the patients of the hearing, and the risk of facial nerve injury very small. The arcuate eminence is often considered a sign of positioning on the canal. By CT before surgery to determine the relationship of semicircular canal and understanding of arcuate eminence and superior semicircular canal for safe removal of internal auditory canal above the bone is very important. Seo on 60 adult temporal bone research, found that the arcuate eminence is 48% in the lateral semicircular canal on the location, relative to 17%, inside is 12%, 17% is unintelligible. On the surface of the petrous bone canal distance is 0 ~ 3mm, usually located just below the surface of the petrous bone.

The combined approach presigmoid and retrosigmoid approach, applicable to involve the whole slope of the tumor, can intratumoral decompression through the former, through the latter from arachnoid cyst tumor interface separation coverage in the brainstem. In addition, through the former can identify the lateral cranial nerve, the use of the latter to identify the brain within the brain stem close to the brain stem, anatomical and functional protection of the brain is helpful. Presigmoid approach combined with anterior resection of petrous bone can be extended to the neutralization of the posterior fossa lesions; combined subtemporal preauricular incision, infratemporal fossa, glossopharyngeal, vagus nerve and provides exposure to the jugular bulb; and far lateral approach, and removal of the occipital condyle outside 1 / 3 extends downward to expose the suboccipital triangle and the posterior arch, resection of foramen magnum lesions.

The surgical technique of petroclival meningiomas is very important, and it is necessary to know the anatomical relationship of petroclival region and have rich experience in micromanipulation. Placed in the preoperative lumbar puncture drainage, or intraoperative application of mannitol can significantly reduce brain pressure, reduce the damage caused by the side pull pull. The treatment of meningiomas in the early stage can effectively avoid the disappearance of arachnoid interface caused by persistent tumor hemorrhage. Tumor growth will be stretched or wrapped around the nerves and blood vessels, especially tumor recurrence, will destroy the arachnoid interface, brainstem leptomeningeal invasion. Surgery should be carefully distinguished and protected. The tumor capsule wall should not be separated from the nerve, vascular adventitia and brain stem. Surgical reconstruction and closure of the skull base are as important as craniotomy. A group of 589 patients with skull base tumors showed temporal bone surgery statistics, postoperative cerebrospinal fluid leakage occurred in 4% ~ 8%. Postoperative cerebrospinal fluid leakage can lead to poor wound healing and fatal meningitis, prevention is very important. Some studies have shown that cerebrospinal fluid drainage is performed before operation. After operation, the mastoid chamber is covered with wax, and the temporalis muscle flap with blood vessel is covered in the mastoid defect area. However, the most serious complication of the repair is the absence of muscle flap and permanent injury of facial nerve. Complications such as local infection, hematoma, facial nerve paralysis, skin donor area and other complications may also occur. Traditionally, fat tamponade and a portion of the temporalis muscle flap were used to repair the defect, but with the loss of muscle and fat, the result was a permanent deformity in the posterior region. It has been advocated that thin titanium mesh and bone cement, or poly (methyl methacrylate) (PMMA) be used to repair bone defects, but the long-term immune response of this kind of material should be observed. Jia modified transpetrosal presigmoid approach, put forward the double craniotomy to avoid bone defect caused by resection of invalid and mastoid cavity, can reduce the probability of injury and dural venous sinus, achieved good results.

The most common complications after the operation of skull base were cranial nerve dysfunction, especially the trigeminal nerve, facial nerve and the posterior cranial nerves, which caused the swallowing dysfunction and facial paralysis. Zhu used alone or in combination with tentorium of cerebellum and occipital temporal under the retrosigmoid keyhole approach, can effectively reduce the surgical trauma, tumor resection, minimize postoperative complications.

Neurophysiological monitoring can provide significant support for the protection of brain stem and nerve function. Brainstem auditory evoked potential (BAEP) is widely used to monitor the responses and functions of the auditory nerve and brainstem in the cerebellopontine angle region. The sudden loss of BAEP is associated with the loss of hearing loss. BAEP wave I-V prolonged latency and amplitude of wave III - V reduction is a sensitive indicator of brainstem damage. EMG can be used to monitor trigeminal nerve, facial nerve and caudal nerve, and they are sensitive to the stimulation signal. In the past 20 years, stereotactic radiosurgery has been developed as an alternative treatment for tumors with a diameter below 3.0cm or residual tumor after surgery. Its application depends on a number of factors, including the size and location of the residual tumor, the age of the patient, and the pathological features of the tumor. It is effective for small to medium sized, symptomatic, newly diagnosed or recurrent brain tumors. Especially in meningioma, the control rate was 97% in grade WHO, grade II, grade III, grade III, grade 3, grade 1, grade 1, grade 1, grade 1, grade 3, grade 17%. 10 years later, the control rate of grade I tumors was 91%.

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