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James K. Liu and Robert W. Jyung

Large acoustic neuromas, greater than 3 cm, can be technically challenging tumors to remove because of their intimate relationship with the brainstem and surrounding cranial nerves. Successful tumor resection involves functional preservation of the facial nerve and neurovascular structures. The translabyrinthine approach is useful for surgical resection of acoustic neuromas of various sizes in patients with poor preoperative hearing. The presigmoid surgical corridor allows direct exposure of the tumor in the cerebellopontine angle without any fixed cerebellar retraction. Early identification of the facial nerve at the fundus facilitates facial nerve preservation. Large acoustic tumors can be readily removed with a retractorless translabyrinthine approach using dynamic mobilization of the sigmoid sinus. In this operative video atlas report, the authors demonstrate their operative nuances for resection of a large acoustic neuroma via a translabyrinthine approach using a retractorless technique. Facial nerve preservation is achieved by maintaining a plane of dissection between the tumor capsule and the tumor arachnoid so that a layer of arachnoid protects the blood supply to the facial nerve. Multilayered closure is achieved with a fascial sling technique in which an autologous fascia lata graft is sutured to the dural defect to suspend the fat graft in the mastoidectomy defect. We describe the step-by-step technique and illustrate the operative nuances and surgical pearls to safely and efficiently perform the retractorless translabyrinthine approach, tumor resection, facial nerve preservation, and multi-layered reconstruction of the skull base dural defect to prevent postoperative cerebrospinal fluid leakage.

The video can be found here: http://youtu.be/ros98UxqVMw.

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James K. Liu and Robert W. Jyung

Cholesterol granulomas are cystic lesions that typically arise in the petrous apex as a result of an inflammatory giant-cell reaction to cholesterol crystal deposits that are formed when normal aeration and drainage of temporal bone air cells become occluded resulting in transudation of blood into the petrous air cells. Surgical strategies include simple cyst decompression, radical excision of the cyst wall, or fenestration and drainage with silastic tubing. The authors present a giant cholesterol granuloma compressing the cerebellopontine angle and brainstem in a 35 year-old male who presented with progressive facial nerve weakness, sensorineural hearing loss, and vertigo. A combined transmastoid middle fossa extradural approach was performed to remove the cyst contents and decompress the brain-stem. A near total excision of the cyst wall was achieved with a small remnant adherent to the posterior fossa dura. Two separate silastic catheters were placed into the cyst cavity to provide “dual exhaust” drainage. One catheter drained the cyst cavity into the sphenoid sinus via a window made in the anteromedial triangle between V1 and V2. The second catheter drained the cyst cavity into the mastoidectomy cavity and middle ear. Postoperative MRI demonstrated regression of the cyst and excellent decompression of the brainstem. The patient experienced return of normal facial nerve function while hearing loss remained unchanged. He remained free of recurrence at 4 years postoperatively. The theoretical advantages of cyst wall removal combined with dual catheter drainage are longer term patency of cyst drainage and decrease of cyst recurrence. In this operative video atlas report, we describe the step-by-step technique and illustrate the operative nuances and surgical pearls to safely and efficiently perform the “dual exhaust” catheter drainage and resection of a giant cholesterol granuloma via a combined transmastoid middle fossa approach.

The video can be found here: http://youtu.be/iZpYBP26ghA.

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James K. Liu, Smruti K. Patel, Amanda J. Podolski, and Robert W. Jyung

Reconstruction of presigmoid dural defects after resection of acoustic neuromas via the translabyrinthine approach is paramount to prevent postoperative CSF leakage. However, primary dural reapproximation and achieving a watertight closure of the dural defect in this anatomical region are quite difficult. Standard closure techniques after the translabyrinthine approach often involve packing an abdominal fat graft that plugs the dural defect and mastoidectomy cavity. This technique, however, may pose the risk of direct compression of the fat graft on the facial nerve and brainstem. Nonetheless, even with the evolution in dural repair techniques, postoperative CSF leaks can still occur and provide a route for infection and meningitis. In this report, the authors describe a novel dural “sling” reconstruction technique using autologous fascia lata to repair presigmoid dural defects created after translabyrinthine resection of acoustic neuromas. The fascia lata is sewn to the edges of the presigmoid dural defect to create a sling to suspend the fat graft within the mastoidectomy defect. A titanium mesh plate embedded in porous polyethylene is secured over the mastoidectomy defect to apply pressure to the fat graft. In the authors' experience, this has been a successful technique for dural reconstruction after translabyrinthine removal of acoustic neuromas to prevent postoperative CSF leakage. There were no cases of CSF leakage in the first 8 patients treated using this technique. The operative details and preliminary results of this technique are presented.

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Ali Tayebi Meybodi, Robert W. Jyung, and James K. Liu

In this illustrative video, the authors demonstrate retrosigmoid resection of a giant cystic vestibular schwannoma using the subperineural dissection technique to preserve facial nerve function. This thin layer of perineurium arising from the vestibular nerves is used as a protective buffer to shield the facial and cochlear nerves from direct microdissection trauma. A near-total resection was achieved, and the patient had an immediate postoperative House-Brackmann grade I facial nerve function. The operative nuances and pearls of technique for safe cranial nerve and brainstem dissection, as well as the intraoperative decision and technique to leave the least amount of residual adherent tumor, are demonstrated.

The video can be found here: https://stream.cadmore.media/r10.3171/2021.7.FOCVID21128

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Renuka K. Reddy, Rohit K. Reddy, Robert W. Jyung, Jean Anderson Eloy, and James K. Liu

A century ago an ambitious young anatomist in Rome, Primo Dorello, who sought to understand the cause of abducent nerve palsy that often occurred in patients with severe middle ear infections, conducted intricate studies on the intracranial course of the nerve. In his findings, he identified that the abducent nerve passes through a narrow sinus near the apex of the petrous bone, which formed an osteofibrous canal. Dorello suggested that in this enclosed region the abducent nerve may be particularly vulnerable to compression due to the vascular edema accompanying the infection. Although his work was widely appreciated, it was not well received by all. Interestingly, Giuseppe Gradenigo, one of the most prominent Italian otologists of the early 20th century, who was known for his work on a triad of symptoms (Gradenigo’s syndrome) that accompanies petrous apicitis, a result of severe middle ear infections, was obstinate in his criticism of Dorello’s findings. Thus a scientific duel began, with a series of correspondence between these two academics—one who was relatively new to the otological community (Dorello) and one who was well reputed in that community (Gradenigo). The disagreement ultimately ebbed in 1909, when Dorello published a report in response to Gradenigo’s criticisms and convinced Gradenigo to change his views.

Today Dorello’s canal is widely recognized as a key landmark in skull base surgery of the petroclival region and holds clinical significance due to its relation to the abducent nerve and surrounding vascular structures. Yet, although academics such as Dorello and Gradenigo are recognized for their work on the canal, it is important not to forget the others throughout history who have contributed to the modern-day understanding of this anatomical structure. In fact, although the level of anatomical detail found in Dorello’s work was previously unmatched, the first description of the canal was made by the experienced Austrian anatomist Wenzel Leopold Gruber in 1859, almost 50 years prior to Dorello’s landmark publication. Another critical figure in building the understanding of Dorello’s canal was Harris Holmes Vail, a young otolaryngologist from Harvard Medical School, who in 1922 became the first person to describe Dorello’s canal in the English language. Vail conducted his own detailed anatomical studies on cadavers, and his publication not only reaffirmed Dorello’s findings but also immortalized the eponym used today—“Dorello’s canal.”

In this article the authors review the life and contributions of Gruber, Dorello, Gradenigo, and Vail, four men who played a critical role in the discovery of Dorello’s canal and paved the way toward the current understanding of the canal as a key clinical and surgical entity.

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Ibrahim Hussain, Qasim Husain, Soly Baredes, Jean Anderson Eloy, Robert W. Jyung, and James K. Liu

Paragangliomas are rare, slow-growing tumors that frequently arise in the head and neck, with the carotid bodies and temporal bone of the skull base being the most common sites. These neoplasms are histologically similar to pheochromocytomas that form in the adrenal medulla and are divided into sympathetic and parasympathetic subtypes based on functionality. Skull base and head and neck region paragangliomas (SHN-PGs) are almost always derived from parasympathetic tissue and rarely secrete catecholamines. However, they can cause significant morbidity by mass effect on various cranial nerves and major blood vessels. While surgery for SHN-PG can be curative, postoperative deficits and recurrences make these lesions challenging to manage. Multiple familial syndromes predisposing individuals to development of paragangliomas have been identified, all involving mutations in the succinate dehydrogenase complex of mitochondria. Mutations in this enzyme lead to a state of “pseudohypoxia” that upregulates various angiogenic, survival, and proliferation factors. Moreover, familial paraganglioma syndromes are among the rare inherited diseases in which genomic imprinting occurs. Recent advances in gene arrays and transcriptome/exome sequencing have identified an alternate mutation in sporadic SHN-PG, which regulates proto-oncogenic pathways independent of pseudohypoxia-induced factors. Collectively these findings demonstrate that paragangliomas of the skull base and head and neck region have a distinct genetic signature from sympathetic-based paragangliomas occurring below the neck, such as pheochromocytomas. Paragangliomas serve as a unique model of primarily surgically treated neoplasms whose future will be altered by the elucidation of their genomic complexities. In this review, the authors present an analysis of the molecular genetics of SHN-PG and provide future directions in patient care and the development of novel therapies.

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Richard F. Schmidt, Zain Boghani, Osamah J. Choudhry, Jean Anderson Eloy, Robert W. Jyung, and James K. Liu

With the relatively recent increase in the use of MRI techniques, there has been a concurrent rise in the number of vestibular schwannomas (VSs) detected as incidental findings. These incidental VSs may be prevalent in up to 0.02%–0.07% of individuals undergoing MRI and represent a significant portion of all diagnosed VSs. The management of these lesions poses a significant challenge for practitioners. Most incidental VSs tend to be small and associated with minimal symptoms, permitting them to be managed conservatively at the time of diagnosis. However, relatively few indicators consistently predict tumor growth and patient outcomes. Furthermore, growth rates have been shown to vary significantly over time with a large variety of long-term growth patterns. Thus, early MRI screening for continued tumor growth followed by repeated MRI studies and clinical assessments throughout the patient's life is an essential component in a conservative management strategy. Note that tumor growth is typically associated with a worsening of symptoms in patients who undergo conservative management, and many of these symptoms have been shown to significantly impact the patient's quality of life. Specific indications for the termination of conservative management vary across studies, but secondary intervention has been shown to be a relatively safe option in most patients with progressive disease. Patients with incidental VSs will probably qualify for a course of conservative management at diagnosis, and regular imaging combined with the expectation that the tumor and symptoms may change at any interval is crucial to ensuring positive long-term outcomes in these patients. In this report, the authors discuss the current literature pertaining to the prevalence of incidental VSs and various considerations in the management of these lesions. It is hoped that by incorporating an understanding of tumor growth, patient outcomes, and management strategies, practitioners will be able to effectively address this challenging disease entity.