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Ahmed Mohyeldin, Jayakar V. Nayak and Juan C. Fernandez-Miranda

Over the past three decades, endoscopic endonasal surgery has unlocked new corridors to treat a wide spectrum of ventral skull base lesions. Tuberculum sella meningiomas represent one of the most ideal pathologies for ventral skull base access. Traditionally, these lesions were approached primarily through various subfrontal and frontal-lateral transcranial approaches that have unfortunately been shown to be associated with worsening visual decline postoperatively. The endoscopic endonasal approach is now being attempted by more surgeons and leverages an infrachiasmatic trajectory that provides direct access to the tuberculum sella where most of the vascular supply for these lesions can be taken early, facilitating more efficient surgical resection and mitigating the risk of optic nerve injury. Here we review a challenging case of a large (∼3 cm) tuberculum sella meningioma, encasing critical vessels off the circle of Willis and resected via an endoscopic endonasal approach. We discuss the technical nuances and relevant surgical anatomy of this approach and highlight important considerations in the safe and successful removal of these meningiomas. We show that certain tumors that appear to encase the supraclinoidal carotid artery can be fully resected via an endonasal approach with precise surgical technique and adequate exposure. Furthermore, this case illustrates the risk of injuring a key perforating vessel from the anterior communicating artery complex, called the subcallosal artery. Injury to this vessel is highly associated with tumors like the one presented here that extend into the suprachiasmatic space between the optic chiasm and the anterior communicating complex. Meticulous surgical dissection is required to preserve this perforating vessel as well as branches from the superior hypophyseal artery. Finally, we review our current closure techniques for these challenging approaches and discuss the use of a lumbar drain for 3 days to lower CSF leak rates.

The video can be found here: https://youtu.be/mafyXi5B0MA.

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Antonio Meola, Ayhan Comert, Fang-Cheng Yeh, Sananthan Sivakanthan and Juan C. Fernandez-Miranda

OBJECT

The dentatorubrothalamic tract (DRTT) is the major efferent cerebellar pathway arising from the dentate nucleus (DN) and decussating to the contralateral red nucleus (RN) and thalamus. Surprisingly, hemispheric cerebellar output influences bilateral limb movements. In animals, uncrossed projections from the DN to the ipsilateral RN and thalamus may explain this phenomenon. The aim of this study was to clarify the anatomy of the dentatorubrothalamic connections in humans.

METHODS

The authors applied advanced deterministic fiber tractography to a template of 488 subjects from the Human Connectome Project (Q1–Q3 release, WU-Minn HCP consortium) and validated the results with microsurgical dissection of cadaveric brains prepared according to Klingler’s method.

RESULTS

The authors identified the “classic” decussating DRTT and a corresponding nondecussating path (the nondecussating DRTT, nd-DRTT). Within each of these 2 tracts some fibers stop at the level of the RN, forming the dentatorubro tract and the nondecussating dentatorubro tract. The left nd-DRTT encompasses 21.7% of the tracts and 24.9% of the volume of the left superior cerebellar peduncle, and the right nd-DRTT encompasses 20.2% of the tracts and 28.4% of the volume of the right superior cerebellar peduncle.

CONCLUSIONS

The connections of the DN with the RN and thalamus are bilateral, not ipsilateral only. This affords a potential anatomical substrate for bilateral limb motor effects originating in a single cerebellar hemisphere under physiological conditions, and for bilateral limb motor impairment in hemispheric cerebellar lesions such as ischemic stroke and hemorrhage, and after resection of hemispheric tumors and arteriovenous malformations. Furthermore, when a lesion is located on the course of the dentatorubrothalamic system, a careful preoperative tractographic analysis of the relationship of the DRTT, nd-DRTT, and the lesion should be performed in order to tailor the surgical approach properly and spare all bundles.

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Juan C. Fernandez-Miranda, Carlos D. Pinheiro-Neto, Paul A. Gardner and Carl H. Snyderman

The authors present the technical and anatomical nuances needed to perform an endoscopic endonasal removal of a tuberculum sellae meningioma. The patient is a 47-year-old female with headaches and an incidental finding of a small tuberculum sellae meningioma with no vascular encasement, no optic canal invasion, but mild inferior to superior compression of the cisternal segment of the left optic nerve. Neuroophthalmology assessment revealed no visual defects. Treatment options included clinical observation with imaging follow-up studies, radiosurgery, and resection. The patient elected to undergo surgical removal and an endonasal endoscopic approach was the preferred surgical option.

Preoperative radiological studies showed the presence of an osseous ring between the left middle and anterior clinoids, the so-called carotico-clinoidal ring. The surgical implications of this finding and its management are illustrated. The surgical anatomy of the suprasellar region is reviewed, including concepts such as the chiasmatic sulcus and limbus sphenoidale, medial and lateral optico-carotid recesses, and the paraclinoidal and supraclinoidal segments of the internal carotid artery. Emphasis is made in the importance of exposing the distal dural ring of the internal carotid artery and the precanalicular segment of the optic nerve for adequate intradural dissection. The endonasal route allows for early coagulation of the tumor meningeal supply and extensive resection of dural attachments, and importantly, provides an inferior to superior access to the infrachiasmatic region that facilitates complete tumor removal without any manipulation of the optic nerve. The lateral limit of dural removal is formed by the distal dural ring, which is gently coagulated after the tumor is resected. A 45° scope is used to inspect for any residual tumor, in particular at the entrance of the optic nerve into the optic canal and at the most anterior margin of the exposure (limbus sphenoidale). The steps for reconstruction are detailed and include intradural placement of dural substitute and extradural placement of the nasoseptal flap. The nuances for proper harvesting, positioning, and reinforcement of the flap are described. No lumbar drain was used.

The patient had an uneventful recovery with no CSF leak or any other complications. Imaging follow-up at 6 months showed complete removal of the tumor. The patient had no sinonasal or neurological symptoms, and olfaction was fully preserved.

The video can be found here: http://youtu.be/kkuV-yyEHMg.

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Danilo Silva, Moshe Attia and Theodore H. Schwartz

Open access

Juan C. Fernandez-Miranda, James J. Evans, Paul A. Gardner, Carl H. Snyderman and Pablo F. Recinos

Open access

Ahmed Mohyeldin, Peter Hwang, Gerald A. Grant and Juan C. Fernandez-Miranda

Pediatric craniopharyngiomas that were once thought to be inoperable or considered only for salvage medical therapy are now being reconsidered for aggressive surgical resection via endoscopic endonasal approaches. Here we review the operative video case of an 11-year-old with a giant complex craniopharyngioma that was resected via an endoscopic endonasal approach. Due to the extent of tumor burden near the basilar apex, a transclival approach was necessary. To accomplish this, a wide sphenoidotomy, posterior ethmoidectomy, and resection of the middle turbinate were necessary to create enough working space for the resection. We also highlight several key innovations in pediatric endoscopic endonasal surgery management and underscore a multidisciplinary approach that allows for the safe and successful treatment of these lesions. Our multidisciplinary team involves an experienced fellowship-trained endoscopic skull base surgeon and otolaryngologist, as well as a pediatric neurosurgeon, pediatric endocrinologist, pediatric anesthesiologist, and pediatric intensivists who play important roles in the preoperative, intraoperative, and postoperative phases of care of the patient. Finally, we discuss critical surgical decision points including pituitary transposition, which has a lot of conceptual appeal when it is anatomically feasible but unfortunately, in our experience, has low functional preservation rates. Initially, we always aim to utilize pituitary transposition for tuberoinfundibular craniopharyngiomas, and once the relationship between the tumor and the stalk is determined, a decision on whether to preserve or sacrifice the stalk and pituitary gland is made. In this particular case, there was a salvageable stalk and the transposition was performed knowing that the chances for functional preservation were low.

The video can be found here: https://youtu.be/ClL73FU5QIU.

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David T. Fernandes Cabral, Georgios A. Zenonos, Juan C. Fernandez-Miranda, Eric W. Wang and Paul A. Gardner

OBJECTIVE

Iatrogenic tumor seeding after open surgery for chordoma has been well described in the literature. The incidence and particularities related to endoscopic endonasal surgery (EES) have not been defined.

METHODS

The authors retrospectively reviewed their experience with EES for clival chordoma, focusing on cases with iatrogenic seeding. The clinical, radiographic, pathological, and molecular characterization data were reviewed.

RESULTS

Among 173 EESs performed for clival chordomas at the authors’ institution between April 2003 and May 2016, 2 cases complicated by iatrogenic seeding (incidence 1.15%) were identified. The first case was a 10-year-old boy, who presented 21 months after an EES for a multiply recurrent clival chordoma with a recurrence along the left inferior turbinate, distinct from a right petrous apex recurrence. Both appeared as a T2-hypertintense, T1-isointense, and heterogeneously enhancing lesion on MRI. Resection of the inferior turbinate recurrence and debulking of the petrous recurrence were both performed via a purely endoscopic endonasal approach. Unfortunately, the child died 2 years later due progression of disease at the primary site, but with no sign of progression at the seeded site. The second patient was a 79-year-old man with an MRI-incompatible pacemaker who presented 19 months after EES for his clival chordoma with a mass involving the floor of the left nasal cavity that was causing an oro-antral fistula. On CT imaging, this appeared as a homogeneously contrast-enhancing mass eroding the hard palate inferiorly, the nasal septum superiorly, and the nasal process of the maxilla, with extension into the subcutaneous tissue. This was also treated endoscopically (combined transnasal-transoral approach) with resection of the mass, and repair of the fistula by using a palatal and left lateral wall rotational flap. Adjuvant hypofractionated stereotactic CyberKnife radiotherapy was administered using 35 Gy in 5 fractions. No recurrence was appreciated endoscopically or on imaging at the patient’s last follow-up, 12 months after this last procedure. In both cases, pathological investigation of the original tumors revealed a fairly aggressive biology with 1p36 deletions, and high Ki-67 levels (10%–15%, and > 20%, respectively). The procedures were performed by a team of right-handed surgeons (otolaryngology and neurosurgery), using a 4-handed technique (in which the endoscope and suction are typically passed through the right nostril, and other instruments are passed through the left nostril without visualization).

CONCLUSIONS

Although uncommon, iatrogenic seeding occurs during EES for clival chordomas, probably because of decreased visualization during tumor removal combined with mucosal trauma and exposure of subepithelial elements (either inadvertently or because of mucosal flaps). In addition, tumors with more aggressive biology (1p36 deletions, elevated Ki-67, or both) are probably at a higher risk and require increased vigilance on surveillance imaging and endoscopy. Further prospective studies are warranted to evaluate the authors’ proposed strategies for decreasing the incidence of iatrogenic seeding after EES for chordomas.

Open access

Kumar Abhinav, David Hong, Carol H. Yan, Peter Hwang, and and Juan C. Fernandez-Miranda

A 14-year-old boy had undergone an orbitozygomatic craniotomy for a pontine lesion. There was growth on surveillance imaging with involvement of posterior clinoids, clivus, and left pons suggestive of chordoma (Fernandez-Miranda et al., 2014b). An endoscopic endonasal approach was undertaken involving full upper and midclival exposure including bilateral posterior clinoidectomy (Fernandez-Miranda et al., 2014a; Truong et al., 2019a, 2019b). The internal carotid artery was skeletonized to maximize exposure and facilitate safe resection. The tumor was removed from between the dural layers of the midclivus while preserving the interdural abducens nerve (Barges-Coll et al., 2010). The brainstem component was resected while preserving the pontine perforators. Postoperative diagnosis was chordoma with MRI demonstrating complete resection. The patient was intact postoperatively.

The video can be found here: https://youtu.be/g6SQ5JVK0Ko.

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Huy Q. Truong, Stefan Lieber, Edinson Najera, Joao T. Alves-Belo, Paul A. Gardner and Juan C. Fernandez-Miranda

OBJECTIVE

The medial wall of the cavernous sinus (CS) is often invaded by pituitary adenomas. Surgical mobilization and/or removal of the medial wall remains a challenge.

METHODS

Endoscopic endonasal dissection was performed in 20 human cadaver heads. The configuration of the medial wall, its relationship to the internal carotid artery (ICA), and the ligamentous connections in between them were investigated in 40 CSs.

RESULTS

The medial wall of the CS was confirmed to be an intact single layer of dura that is distinct from the capsule of the pituitary gland and the periosteal layer that forms the anterior wall of the CS. In 32.5% of hemispheres, the medial wall was indented by and/or well adhered to the cavernous ICA. The authors identified multiple ligamentous fibers that anchored the medial wall to other walls of the CS and/or to specific ICA segments. These parasellar ligaments were classified into 4 groups: 1) caroticoclinoid ligament, spanning from the medial wall and the middle clinoid toward the clinoid ICA segment and anterior clinoid process; 2) superior parasellar ligament, connecting the medial wall to the horizontal cavernous ICA and/or lateral wall of the CS; 3) inferior parasellar ligament, bridging the medial wall to the anterior wall of the CS or anterior surface of the short vertical segment of the cavernous ICA; and 4) posterior parasellar ligament, which anchors the medial wall to the short vertical segment of the cavernous ICA and/or the posterior carotid sulcus. The caroticoclinoid ligament and inferior parasellar ligament were present in most CSs (97.7% and 95%, respectively), while the superior and posterior parasellar ligaments were identified in approximately half of the CSs (57.5% and 45%, respectively). The caroticoclinoid ligament was the strongest and largest ligament, and it was typically assembled as a group of ligaments with a fan-like arrangement. The inferior parasellar ligament was the first to be encountered after opening the anterior wall of the CS during an interdural transcavernous approach.

CONCLUSIONS

The authors introduce a classification of the parasellar ligaments and their role in anchoring the medial wall of the CS. These ligaments should be identified and transected to safely mobilize the medial wall away from the cavernous ICA during a transcavernous approach and for safe and complete resection of adenomas that selectively invade the medial wall.

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Juan C. Fernández-Miranda, Albert L. Rhoton Jr., Yukinari Kakizawa, Chanyoung Choi and Juan Álvarez-Linera

Object

The goal in this study was to examine the microsurgical and tractographic anatomy of the claustrum and its projection fibers, and to analyze the functional and surgical implications of the findings.

Methods

Fifteen formalin-fixed human brain hemispheres were dissected using the Klingler fiber dissection technique, with the aid of an operating microscope at × 6–40 magnification. Magnetic resonance imaging studies of 5 normal brains were analyzed using diffusion tensor (DT) imaging–based tractography software.

Results

Both the claustrum and external capsule have 2 parts: dorsal and ventral. The dorsal part of the external capsule is mainly composed of the claustrocortical fibers that converge into the gray matter of the dorsal claustrum. Results of the tractography studies coincided with the fiber dissection findings and showed that the claustrocortical fibers connect the claustrum with the superior frontal, precentral, postcentral, and posterior parietal cortices, and are topographically organized. The ventral part of the external capsule is formed by the uncinate and inferior occipitofrontal fascicles, which traverse the ventral part of the claustrum, connecting the orbitofrontal and prefrontal cortex with the amygdaloid, temporal, and occipital cortices. The relationship between the insular surface and the underlying fiber tracts, and between the medial lower surface of the claustrum and the lateral lenticulostriate arteries is described.

Conclusions

The combination of the fiber dissection technique and DT imaging–based tractography supports the presence of the claustrocortical system as an integrative network in humans and offers the potential to aid in understanding the diffusion of gliomas in the insula and other areas of the brain.