Neurological Surgery最新文献

Glomus tumors, also known as paragangliomas, were previously classified as benign tumors; however, the WHO classification of endocrine and neuroendocrine tumors 4^th edition no longer classified paragangliomas as benign and malignant given any lesion can have metastatic potential. Temporal bone glomus tumors are classified into glomus tympanicum tumors and glomus jugulare tumors. Complete surgical resection is preferred for glomus tympanicum tumors whereas, for glomus jugulare tumors, it is necessary to evaluate age, tumor extension, hearing, and neurological symptoms to determine treatment strategy. In cases of catecholamine production, cranial nerve paralysis, young age, and SDHB gene mutations, surgery should be considered. The infratemporal fossa type A approach is one of the main surgical approaches for glomus jugulare tumors. Management of glomus jugulare tumors requires a thorough understanding of pathophysiology of the tumor including biochemistry, genetics, and metastasis. Surgery, radiotherapy, and active surveillance are treatment options, and should be individualized to patients to maintain quality of life.

Hemostasis is a critical skill in cerebellopontine angle (CPA) tumor surgery given its deep anatomical location, narrow surgical corridor, and proximity to vital neurovascular structures. Inadequate bleeding control can obscure the operative field, increase the risk of cranial nerve injury, and lead to life-threatening complications, such as brainstem infarction or cerebellar swelling. This article outlines the key principles of hemostasis at each step of CPA tumor resection, from the preoperative setting and craniotomy to tumor debulking and dissection. Based on our surgical experience, we present detailed technical strategies for achieving safe and effective hemostasis during meningioma, vestibular schwannoma, and hemangioblastoma resection. Practical tips include the management of emissary veins; the preservation of draining veins, such as the petrosal vein; and staged tumor resection adapted to the vascular supply. Videos of representative cases are included to demonstrate hemostatic techniques in real surgical settings. Through emphasizing complete bleeding control at each stage before proceeding to the next, this article aims to provide practical guidance for neurosurgeons in training and promote safer skull base tumor surgery.

Two types of intraoperative monitoring of the cranial nerve motor function have been widely used during the removal of cerebellopontine angle tumors. The first type involves anatomical mapping through directly stimulating the cranial nerve to confirm its location. The second type involves monitoring motor function preservation through direct stimulation-compound muscle action potential (Ds-CMAP), motor-evoked potential (MEP) using transcranial electrical stimulation, and free-run electromyography (EMG). Particularly for patients with vestibular schwannomas, anatomical mapping is important to confirm the location of the facial nerve, which is likely to be deviated or compressed by a tumor. Ds-CMAP monitoring adjacent to the root exit zone of the facial nerve is useful for detecting facial nerve damage. Monitoring facial MEP, induced using transcranial electrical stimulation, is also useful in predicting postoperative facial motor function. Free-run electromyography EMG provides real-time monitoring of facial motor function; however, objective evaluation is challenging intraoperatively. Brainstem auditory evoked potential monitoring has been widely used to preserve hearing during the removal of cerebellopontine angle tumors. Cochlear nerve action potentials recorded directly from the cochlear nerve provide more useful monitoring for predicting postoperative hearing function. To preserve the motor function of the glossopharyngeal and vagus nerves, both pharyngeal MEP recorded from the swallowing muscle and vagus nerve MEP recorded from the vocal cord using transcranial electrical stimulation are useful in predicting postoperative swallowing function. A clear understanding of the purposes, methods, and evaluations of various types of cranial nerve monitoring during the removal of cerebellopontine angle tumors is essential.

Preoperative embolization of brain tumors has been reported to be useful in reducing blood loss during resection, softening the tumor, and shortening the operation time by occluding blood-rich tumor nutrient vessels. This applies to skull base tumors, which are deep and difficult to expand in the operative field. Cerebellopontine angle tumors often have the petrosal branch of the middle dural artery, ascending pharyngeal artery, meningohypophyseal trunk, and inferolateral trunk as feeding vessels. Caution is required because these blood vessels are involved in the vasa nervorum and dangerous anastomosis. Embolization of these vessels can be performed safely and effectively by guiding a small catheter as far as possible to the periphery without wedging and injecting a high dilution of Embosphere^® 500-700µm.

Cerebellopontine (CP) angle meningiomas are surgically challenging because of their deep-seated location and proximity to the cranial nerves and vessels. Surgical approaches suitable for treating these tumors are described in detail in this article. CP angle meningiomas can be classified into six subtypes based on the tumor attachment location: 1)petrotentrial, 2)anterior petrous, 3)posterior petrous, 4)petroclival, 5)inferior petroclival or jugular tubercle, and 6)pure clival meningioma. The suitable approach for each subtype is described.

Surgical and radiotherapeutic interventions for vestibular schwannomas in patients with neurofibromatosis type 2 (NF2) generally yield less favorable outcomes than in sporadic unilateral cases, often hindering hearing preservation. Managing NF2 entails a lifelong series of complex decisions, repeatedly weighing functional preservation against impairment and surveillance against invasive therapeutic interventions. For both patients and their physicians, a critical issue lies in how to maximize functional preservation while simultaneously securing long-term survival. Auditory reconstruction using implantable auditory devices should be considered in cases of severe bilateral hearing loss. In patients with preserved cochlear nerve integrity, cochlear implantation is effective, and treatment strategies should be planned with this option in mind. Clinical trials of bevacizumab for pharmacological treatment are currently ongoing in Japan, and the clinical application of anti-vascular endothelial growth factor receptor vaccine therapy is anticipated.

MRI is the most effective imaging tool for diagnosing cerebellopontine angle tumors, although CT is also useful for evaluating bone changes and detecting calcification. Regarding MRI, it is recommended to efficiently use MR cisternography, a small imaging field of view, and a thin slice thickness. The most common tumor type is acoustic schwannoma, followed by meningioma, trigeminal, facial nerve, jugular foramen schwannoma, paraganglioma, and others. Many of these tumor types can be effectively differentiated by combining various CT and MRI techniques, as stated above, as well as MRA, perfusion imaging, MR digital subtraction angiography, MR spectroscopy, and bone imaging. This article discusses the key MRI and CT findings of major cerebellopontine angle tumors, as well as some representative cases and the corresponding differential diagnoses.

Intracranial epidermoid cysts are congenital benign tumors; however, there is a long-term risk of recurrence if the tumor capsule is left behind perioperatively. Additionally, in cerebellopontine angle surgery, in which cranial nerves and blood vessels are densely concentrated, cranial nerve functions must be preserved besides radical removal of the tumor capsule. Particularly, the optimal surgical field should be obtained under direct visualization to avoid cranial nerve damage due to manipulation over cranial nerves and leaving the tumor behind in the blind spot of the surgical field. Therefore, besides the use of intraoperative monitoring, high surgical skills are required to use four skull base surgical approaches, such as lateral suboccipital retrosigmoid approach (LSO), anterior transpetrosal approach (ATP), combined transpetrosal approach, and ATP and LSO, depending on the size and progression of the tumor. Moreover, this disease should be treated at a specialized facility for skull base surgery.

Cerebellopontine angle tumors are rare, and surgeries for these tumors are challenging. Vestibular schwannomas, which account for 70-80% of cerebellopontine angle tumors, are managed by surgery, stereotactic radiosurgery or radiotherapy, and watchful observation. Surgery for vestibular schwannoma aims for maximal tumor resection while preserving facial and/or hearing function through strict intraoperative neuromonitoring. Surgical outcomes have markedly improved since the centralization of vestibular schwannoma surgery through the Internet and mass media. This chapter outlines the surgical approaches for cerebellopontine angle tumors, including vestibular schwannomas, meningiomas, epidermoid cysts, trigeminal schwannomas, jugular foramen schwannomas, facial nerve schwannomas, hypoglossal schwannomas, and glomus jugulare tumors.

Stereotactic radiation therapy, including stereotactic radiosurgery, is a well-established and effective treatment for cerebellopontine angle tumors such as meningiomas, vestibular schwannomas, trigeminal and jugular foramen schwannomas, and glomus tumors. It offers high rates of tumor control while preserving neurological function, particularly in tumors smaller than 3 cm, which are ideal candidates for stereotactic radiosurgery. Large tumors or those extending beyond the skull base can also be managed effectively using fractionated stereotactic radiation therapy. As such, a multidisciplinary approach that combines surgical resection with stereotactic radiation therapy is a valuable strategy, especially when functional preservation is a key therapeutic goal.