Central diabetes insipidus (CDI) is a neurological pathological condition in which vasopressin synthesis has been compromised. A 52-year-old male presented with a cerebellopontine angle mass not involving the hypothalamic-pituitary axis. Despite vasopressin therapy, the patient produced a total of 8650 mL of urine, with the urine-specific gravity measured at 1.002 near hour 8. A literature review found associations with certain anesthetic drugs that have an increased incidence of CDI, including alpha-2 agonists and sevoflurane. Reports have recommended administering desmopressin over vasopressin, especially for neurosurgery cases that warrant a more extended operative period, given that desmopressin has a longer context-sensitive half-life.

The management of vestibular schwannoma (VS) remains one of the most formidable challenges in neurosurgery owing to the eloquent nature of surrounding anatomy. Although endoscopy-assisted microsurgery has recently gained momentum in cerebellopontine angle region surgery, the feasibility of pure endoscopic technique has been rarely reported. Here we present the operative technique and preliminary outcomes of fully endoscopic retrosigmoid trans-petrosal fissure approach (ER-TPFA) for VS surgery. Clinical data of 36 consecutive cases of VS treated with the ER-TPFA from March 2021 to March 2023 were analyzed. The patients were placed in a modified lateral park-bench position, with the Dandy incision and suboccipital craniotomy performed. With the endoscopic holder, endoscopic procedures were performed using standard two-hand microsurgical techniques by one surgeon. Arachnoidal dissection of the petrosal fissure was performed for identifying the brainstem end of facial nerve and separating the tumor from the cerebellum, without brain retraction seen in traditional microsurgical technique. The tumors had an averaged size of 3.0 cm in diameter. According to the Hannover classification, nearly all the tumors were grade III-IV (97.3%). Using ER-TPFA, 33 patients (91.7%) achieved gross total resection. Anatomic preservation of the facial nerve was achieved in 35 cases, with 33 patients (91.7%) retaining a House-Brackmann score of 1-2 postoperatively. Four out of ten patients still had serviceable hearing 6 months after operation. Postoperatively, there was no post-craniotomy hematoma, cerebellar edema, and new-onset cerebellar ataxia. With a better visualization of the cerebellopontine angle region, ER-TPFA may help preserve facial nerve function and maintain high gross total resection rate while minimizing complications. We believe this retractorless technique can be a safe and effective alternative for the management of VS with satisfactory clinical results.

UNASSIGNED: Accessing the posterior base of the skull is complex because of the vital neurovascular structures in the area. However, the retrosigmoid approach (RSA) offers a solution to this challenge.
UNASSIGNED: To analyze surgical outcome of RSA.
UNASSIGNED: This study involved a retrospective review of patient charts from a single center, focusing on the surgical procedure and outcomes following the operation.
UNASSIGNED: The study included 517 patients suffering from conditions like vestibular schwannomas (VS), metastatic cancers, and trigeminal neuralgia. The most frequent symptoms reported were balance disorders (42.7%), hearing loss (36.5%), walking difficulties (21.2%), headaches (18.9%), facial pain (17.1%), issues with trigeminal nerve function (14.1%), cerebellar dysfunction (13.5%), and facial nerve paralysis (10.2%). The rate of complications stood at 21.1%, with 11.3% of patients needing revision surgery. The median score on the Clavien-Dindo scale was 2, and the rate of mortality related to surgery was 1.0%. Permanent symptom improvement was seen in 72.1% of cases. Temporary new deficits occurred in 43.2% of patients, with facial nerve paralysis being the most common (14.1%). No significant correlation was found between the size of the craniotomy and the extent of tumor resection (p = 0.155), except in the case of VS (p = 0.041). Larger craniotomy sizes were associated with higher rates of complications (p = 0.016), especially CSF leaks (p = 0.006). Complications significantly affected the likelihood and number of new deficits (p < 0.001 for both), particularly postoperative bleeding (p = 0.019, p = 0.001), CSF leaks (p = 0.026, p = 0.039), and hydrocephalus (p = 0.050, p = 0.007).
UNASSIGNED: The potential for complications related to the surgical approach cannot be overlooked. The size of the tumor should not dictate larger surgical approaches due to the associated increase in postoperative complications; a tailored approach that considers the precise tumor location and pathology is crucial for optimizing postoperative outcomes.

Ependymoma occurring at the cerebellopontine (CP) angle is an extremely uncommon sight and poses diagnostic and management dilemmas to neurosurgeons, radiologists, and neuropathologists alike. Moreover, the presence of extensive chondro-osseous metaplastic elements in ependymomas is an exceptionally infrequent histopathological manifestation. However, due to the seldom-seen nature of this histomorphological feature, there is no definite consensus regarding its etiopathogenesis and clinical consequences, and there is an extreme scarcity of literature elucidating its clinicopathological spectrum and prognostic significance. Herein, we illustrate an intriguing clinical tale of a 7-year-old male child with posterior fossa ependymoma, central nervous system (CNS) World Health Organization (WHO) grade 3, arising at the right CP angle and masquerading as a vestibular schwannoma, which in itself is a rare presentation, and additionally, exhibiting extensive chondro-osseous metaplasia, which is a very uncommon histomorphological observation. To the best of the authors\' knowledge and after a comprehensive literature search, the coexistence of these two rare observations has merely been described once in international literature. This case sheds light on and highlights the importance of keeping ependymoma as a possible differential while coming across CP angle space-occupying lesions. They should be diligently distinguished from schwannomas and other masqueraders that typically occur at this site, as they have diverse management and follow-up protocols, with varying prognostic outcomes for the patients. Moreover, this case also unravels and details the clinicopathological characteristics of a scarcely described feature of chondro-osseous metaplasia in ependymomas.

This case report aims to describe the clinical presentation, imaging findings, diagnostic challenges, and management of a patient with a cerebellopontine angle lesion. A 63-year-old woman presented with progressive headaches, tinnitus, right ear pressure, and dizziness. Initial imaging studies (computed tomography and magnetic resonance imaging) suggested either a thrombosed aneurysm or a lipoma. However, advanced imaging with cone beam computed tomography provided a definitive diagnosis of temporal bone exostosis. This case highlights the importance of cone beam computed tomography in diagnosing complex intracranial lesions due to its superior spatial resolution and lower radiation dose.

A meningioma is a rare primary CNS tumor that tends to present more so in females in a slowly progressive fashion. The cavernous sinus and cerebellopontine angle are uncommon locations for meningiomas. We present a case of a meningioma in a 60-year-old female presenting to the emergency department for a sudden onset headache, vertigo, facial paresthesias, and chest pain. Inpatient workup revealed orthostatic hypotension, a meningioma spanning from the left cavernous sinus to the left cerebellopontine angle encasing the left cavernous internal carotid artery on MRI and CTA, and an incidental 12 mm calcified fibroadenoma on CT. Hospital course consisted of supportive treatment, physical rehabilitation, and review of previous imaging to determine need for intervention per consultants\' recommendations. The patient was discharged with an antiplatelet, an antihistamine, appropriate additional medications, a vestibular therapy script, and outpatient referrals for a decision regarding surveillance and intervention. Overall, this case describes some key points. It demonstrates that cavernous sinus and cerebellopontine angle meningiomas can occur simultaneously, especially as a continuous mass, which very few cases have done so far. It also highlights an acute clinical presentation of a meningioma, contrary to the gradually progressive one observed in most instances. Last, but not least, it shows how nonspecific symptoms can lead to unique findings at times.

Considering that most meningiomas are pathologically benign, tumors located in the cerebellopontine angle and petroclival area should be reduced as much as possible, and radiation therapy should be administered if necessary. Consequently, relatively good preservation of cranial nerve function and local lesion control can be expected. However, because the lesions are generally located deep, and are surrounded by various important structures, performing surgical procedures is difficult, and careful management of the surgical strategy is important to avoid complications. Surgical outcomes have dramatically improved with the development of skull base and microsurgical techniques. The main surgical approaches for cerebellopontine angle meningiomas and petroclival meningiomas currently include the anterior and posterior combined transpetrosal, anterior transpetrosal, and lateral suboccipital approaches. Furthermore, with the recent developments in endoscopic surgery, minimally invasive surgery for skull base meningiomas has gradually been introduced. In this article, we explain the preoperative checkpoints, selection of the surgical approach, and surgical techniques for the resection of cerebellopontine angle meningiomas and petroclival meningiomas.

OBJECTIVE: Cerebellopontine angle (CPA) tumors are a common cause of secondary trigeminal neuralgia (TN), characterized by their concealed location, slow progression, and difficulty in early detection. This study aims to explore the clinicopathological characteristics of patients with secondary TN due to CPA tumors to enhance understanding and management of secondary TN.
METHODS: A retrospective analysis was conducted on clinical data and pathological results of 116 patients with CPA tumor-related TN treated at Xiangya Hospital of Central South University from January 1, 2017 to December 31, 2022. The study analyzed the relationship of tumor pathological types with clinical manifestations, tumor location, surgical methods, and treatment outcomes.
RESULTS: Among the cases, 95.7% (111/116) were benign tumors, 3.4% (4/116) were malignant tumors, and 0.9% (1/116) were borderline tumors. Benign tumors were predominantly acoustic neuromas, meningiomas, and schwannomas. Among the patients, 46.6% (54/116) presented with isolated TN, while 53.4% (62/116) exhibited other associated symptoms depending on factors such as tumor growth location and rate. The complete resection rate in this group was over 90%, with 41.4% (48/116) of patients undergoing concurrent microvascular decompression after tumor resection, predominantly for schwannomas. The overall effective rate of surgical treatment reached 93.9%, with schwannomas showing higher efficacy rates compared with acoustic neuromas and meningiomas (P<0.05). The recurrence rate of acoustic neuromas was significantly higher than that of meningiomas and schwannomas (P<0.05).
CONCLUSIONS: CPA tumors are a major cause of secondary TN, predominantly benign, with occasional underdiagnosed malignant tumors. Early diagnosis and treatment significantly impact prognosis. Different tumor types vary in clinical symptoms, surgical approaches, and treatment efficacy. Surgical strategies should balance tumor resection extent and neural function preservation, with microvascular decompression as necessary.
目的: 桥小脑角(cerebellopontine angle，CPA)肿瘤是继发性三叉神经痛(trigeminal neuralgia，TN)的常见病因，其位置隐蔽，进展缓慢，难以早期发现。本研究旨在探讨CPA肿瘤继发性TN患者的临床病理特征，提高对继发性TN诊治的认识。方法: 回顾性分析中南大学湘雅医院2017年1月1日至2022年12月31日收治的116例CPA肿瘤继发TN患者的临床资料和病理结果，分析肿瘤病理类型与临床表现、肿瘤部位、手术方式及疗效的关系。结果: 本组病例中95.7%(111/116)为良性肿瘤，3.4%(4/116)为恶性肿瘤，0.9%(1/116)为交界性肿瘤，良性肿瘤以胆脂瘤、脑膜瘤、神经鞘瘤多见。46.6%(54/116)的患者表现为单纯TN，53.4%(62/116)出现其他伴随症状，这取决于不同类型肿瘤的生长部位、生长速度等因素。本组病例手术全切率在90%以上，41.4%(48/116)的患者在切除肿瘤后同期行微血管减压，其中神经鞘瘤占比最高。手术治疗总体有效率达93.9%，神经鞘瘤的有效率高于胆脂瘤、脑膜瘤(均P<0.05)；胆脂瘤的复发率显著高于脑膜瘤、神经鞘瘤(均P<0.05)。结论: CPA肿瘤是继发性TN的主要病因，以良性肿瘤多见，恶性肿瘤虽少但容易被漏诊，早期诊治对预后影响很大。不同类型肿瘤在临床症状、手术方式、疗效等方面有所不同，手术策略需兼顾肿瘤切除程度及神经功能保护，必要时行微血管减压术。.

BACKGROUND: Fully endoscopic or endoscope-controlled approaches are essentially keyhole approaches in which rigid endoscopes are the sole visualization tools used during the whole procedure. At the early attempts of endoscope-assisted cranial surgery, it was noted that rigid endoscopes enabled overcoming the problem of suboptimal visualization when small exposures are used. The technical specifications and design of the currently available rigid endoscopes are associated with a group of unique features that define the endoscopic view and lay the basis for its superiority over the microscopic view during brain surgery. Fully endoscopic retrosigmoid approach for cerebellopontine angle tumors is a minimally invasive approach that is not routinely practiced by neurosurgeons, with few series published so far. Unfamiliarity with the technique, steep learning curve, and concerns about inadequate exposure, neurovascular injury, and decreased visibility may explain this fact. In this chapter we elaborate on the surgical technique and nuances of the fully endoscopic retrosigmoid approach and present an overview of the published series.
METHODS: From a prospective database of endoscopic procedures maintained by the senior author, clinical data, imaging studies, operative charts, and videos of cases undergoing fully endoscopic retrosigmoid approach for cerebellopontine angle tumors were retrieved and analyzed. The pertinent literature was also reviewed.
RESULTS: The surgical technique of the fully endoscopic retrosigmoid approach was formulated.
CONCLUSIONS: The endoscopic technique has many advantages over the conventional procedures. In our hands, the technique has proven to be feasible, efficient, and minimally invasive with excellent results.

OBJECTIVE: The rhomboid lip is a neural tissue encountered during cerebellopontine angle surgery, with differing shape and extent among individuals. This study aimed to investigate the variation of rhomboid lips during posterior fossa surgery.
METHODS: In this retrospective study, we examined posterior cranial fossa surgeries performed using a retrosigmoid approach. Rhomboid lips were classified according to thickness, extent, and appearance, with some subjected to histological analysis. T2-weighted magnetic resonance imaging of rhomboid lips was conducted.
RESULTS: Among 304 surgeries, rhomboid lips were observed in 75 patients who underwent schwannoma or meningioma resection, facial spasm-related neurovascular decompression, and other surgeries (37, 2, 32, and 4 patients, respectively). Rhomboid lips were categorized based on apparent thickness: thin membranous type, resembling an arachnoid membrane, and thick parenchymal type. Rhomboid lip extension was classified by position relative to the choroid plexus: nonextension, lateral extension, and jugular foramen (41, 22, and 12 patients, respectively). Veins were observed on the rhomboid lip surface in 37 cases. The rhomboid lip was visible in only 1 case (parenchymal jugular foramen type) on magnetic resonance imaging. Histologically, the rhomboid lip comprised an ependymal cell layer, a glial layer, and connecting tissue. The glial layer thickness determined the rhomboid lip thickness, which was greater in the parenchymal type than in the membrane type. In 42 patients, the rhomboid lip was dissected with no complications observed.
CONCLUSIONS: Morphological classification of the rhomboid lip and understanding of its anatomical details contribute to safe surgical field development for neurosurgeons.