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Aaron A. Cohen-Gadol

Epidermoid tumors comprise about 1% of all intracranial tumors. They are congenital lesions that arise from paramedian cisterns within the posterior fossa. These tumors present as heterogeneous hyperintense lesions on FLAIR and homogenous hyperintense lesions on DWI. Surgical resection remains the most accepted form of therapy, but epidermoid tumors may recur. These tumors are well exposed through a traditional retrosigmoid approach. The tumor can be removed relatively easily as it is avascular. However, the propensity of this tumor type to fill the small spaces within basal cisterns and attach to cranial nerves may make its complete resection challenging. Tumors resection has to preserve the surrounding arachnoid membranes encasing the cranial nerves.

The author presents the case of a 42-year-old woman with a 1-year history of imbalance and nystagmus. An MRI revealed a large right-sided CP angle epidermoid tumor filling the ventral brainstem cistern and extending to the contralateral side, compressing the brainstem. The accompanying video illustrates resection of this mass through an extended (exposing the sigmoid sinus) retrosigmoid approach. The author removed the tumor piecemeal while protecting the cranial nerves. Small pieces of affected arachnoid covering the cranial nerves were not significantly manipulated. To excise the tumor along the contralateral paramedian cistern, the author used the space between the V and VII/VII cranial nerves to expose the space contralateral to the basilar artery and remove additional tumor. This maneuver allowed gross total resection of the tumor without a need to employ a more elaborate skull base approach such as petrosectomy. At 3-month follow-up visit after surgery, the patient's neurological exam returned to normal.

The video can be found here: http://youtu.be/CzRb-GUvhog.

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Aaron A. Cohen-Gadol

Anterior third ventricular lesions present with a variety of symptoms related to cerebrospinal fluid flow obstruction and mass effect. Colloid cysts are among the most common lesions in the region. They usually present with ventriculomegaly, leading to headaches, vertigo, or, rarely, decreased mental status due to the development of acute hydrocephalus. Many patients become aware of their asymptomatic colloid cysts during imaging evaluation related to other conditions. Symptomatic cysts require removal, and larger asymptomatic colloid cysts (> 1cm) in younger patients may also need to be excised despite a lack of symptoms.

A variety of surgical routes have been described to access and remove colloid cysts. Endoscopic approaches are least invasive and provide adequate decompression and removal of the cyst wall. However, presence of ventriculomagaly may be necessary to provide adequate working space for endoscopic resection. Transcallosal interhemispheric and transcortical routes are typically reserved for patients with symptomatic or large asymptomatic cysts without any significant hydrocephalus. Transcortical route may carry a slightly increased risk of seizures due to cortical disruption. Interhemispheric transcallosal approach with the use of microsurgical techniques minimizes injury to normal structures. In this video, the author describes his technique for transcallosal resection of a large colloid cyst in the absence of significant ventriculomegaly. Methods to minimize complications are reviewed.

The video can be found here: http://youtu.be/KzC8QYsTKeg.

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Benjamin K. Hendricks and Aaron A. Cohen-Gadol

Epidermoid cysts or tumors comprise 1% of intracranial tumors with a predilection for the cerebellopontine angle or parasellar cisterns. These tumors are derived from an ectopic ectodermal implant seeded between fusing ectodermal surfaces. This results in a benign proliferation of stratified squamous epithelium along a cyst wall with a lumen composed of hyperkeratotic material derived from the desquamating cells. Surgical intervention is the treatment of choice for symptomatic patients. There is no role for radiotherapy or chemotherapy in the treatment of these lesions, including for residual or recurrent disease. The inherent adhesion of the proliferating epithelial lining to surrounding neurovascular structures significantly complicates attempts at gross-total resection. Epidermoid tumors or cysts are rarely reported within the third ventricular region. In this video, the authors demonstrate the technique of right-sided posterior interhemispheric transcallosal approach for maximal resection of a complex recurrent third ventricular epidermoid tumor with lateral ventricular extension.

The video can be found here: https://youtu.be/wbXp7mc0vT4.

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Aaron A. Cohen-Gadol

Intraorbital meningiomas are challenging lesions to excise because of their location and the restricted surgical corridor available due to the presence of important neighboring structures. Lesions located in the posterior one-third of the orbit require skull base approaches for their exposure and safe resection.

Frontoorbital and modified orbitozygomatic (OZ) craniotomies may facilitate the exposure and resection of masses in the posterior intraorbital space. Specifically, the one-piece modified OZ craniotomy provides many advantages of the “full” OZ craniotomy (which includes a more extensive zygomatic osteotomy). The modified OZ approach minimizes the extent of frontal lobe retraction and provides ample amount of space for the surgeon to exploit all the working angles to resect the tumor.

The following video presentation discusses the nuances of technique for resection of an intraorbital meningioma through modified OZ approach and optic nerve decompression. The nuances of technique will be discussed.

The video can be found here: http://youtu.be/fP5X2QNr5qk.