Endoscopic endonasal pituitary transposition for a transdorsum sellae approach to the interpeduncular cistern

Modern management of brainstem cavernous malformations

Over the last 2 decades, there have been dramatic advancements in our understanding of and the ability to treat brainstem cavernous malformations (BCMs). Once thought untreatable, BCMs are now being more aggressively and safely treated microsurgically as a result of advances in monitoring and imaging technologies, as well as refinement of surgical techniques. BCMs deemed inoperable are being treated with radiosurgery, and experience with dosing and targeting has improved the safety of this treatment modality as well. Much work remains to be done, and prospective randomized trials would undoubtedly further existing knowledge.

Extended endoscopic endonasal approach to the suprasellar parachiasmatic cisterns: anatomic study

OBJECTIVE

The objective of this study is to recognize the available endoscopic routes during approaches to the suprasellar region and the surgical endoscopic anatomy of the related neurovascular structures.

MATERIAL AND METHODS

Extended endoscopic endonasal approach to the suprasellar region (EEASR) through the planum sphenoidale was performed in five fresh adult cadavers. The anatomic characteristics of the suprasellar parachiasmatic cisterns were studied and documented following the resection of the planum sphenoidale and opening the dura to expose the anterior incisural space.

RESULTS

Two separate surgical corridors could be used during EEASR: one above and the other below the chiasm. The suprachiasmatic route exposed the gyrus recti, interhemispheric fissure, anterior cerebral artery complex, the lamina terminalis, and through this structure the anterior recess of the third ventricle. The subchiasmatic route exposed the pituitary stalk, superior hypophyseal artery, supraclinoidal internal carotid artery, origin of the ophthalmic artery, anterior choroidal artery, posterior communicating artery, uncus, optic tract, basilar artery and its bifurcation, pons, posterior cerebral artery, superior cerebellar artery, and oculomotor nerve.

CONCLUSION

The EEASR, a minimally invasive route to suprasellar parachiasmatic area, provided wide exposure of the basal cisterns. The surgical areas that were accessed through the subchiasmatic corridor could be divided into a medial part that included the interpeduncular and prepontine cisterns and a lateral part that contained carotid and sylvian cisterns superiorly and the crural and ambient cisterns inferiorly.

Expanded endonasal approaches to middle cranial fossa and posterior fossa tumors

Skull base lesions that involve the middle and posterior cerebral fossae have been historically managed through extensive transcranial approaches. The development of endoscopic endonasal techniques during the past decade has made possible a vast array of alternative routes to the ventral skull base, providing the ability to expose lesions in difficult-to-access regions of the cranial base in a less invasive manner. In this review, the authors detail the endoscopic surgical anatomy and the operative nuances of the expanded endoscopic endonasal approaches to tumors of the middle and posterior cranial fossae. These techniques offer excellent exposure of the targeted regions yielding optimal resections, while avoiding the morbidity associated with transcranial surgical approaches.

Endoscopic anatomy of the oculomotor nerve: defining the blind spot during endoscopic skull base surgery

OBJECTIVE

The objective of this study is to define the endoscopic anatomy of the oculomotor nerve (CN III) and its neurovascular relations in order to facilitate surgical procedures and avoid injury to this nerve during endoscopic endonasal approach to the skull base.

MATERIALS AND METHODS

Endoscopic anatomy of the cavernous sinus was studied in seven fresh adult cadavers bilaterally and the basal cisterns in five fresh adult cadavers. Extended endoscopic endonasal suprasellar approach was performed to expose the oculomotor nerve in the interpeduncular cistern and the endoscopic endonasal transethmoidopterygoidosphenoidal approach to expose the oculomotor nerve within the cavernous sinus.

RESULTS

The extraorbital part of the oculomotor nerve can be divided into three segments in regard to the cisterns and venous spaces that are being transected: the interpeduncular segment, the cisternal segment, and the intercavernous segment. Of these segments, only the cisternal segment could not be exposed since this segment was located at the initial part of the roof of the cavernous sinus, anterolateral to the posterior clinoid, and posteroinferior to the anterior clinoid processes. Thus, cisternal segment of the oculomotor nerve was considered a blind spot during endoscopic approaches to the skull base.

CONCLUSION

We defined the endoscopic anatomy of the CN III and the related neurovascular structures and proposed a new segmental classification of extraorbital oculomotor nerve. Awareness of the endoscopic anatomy and the new segmental classification of the CN III may prove helpful in avoiding the risk of nerve injury during endoscopic endonasal surgery for skull base pathologies.

Three-dimensional and 2-dimensional endoscopic exposure of midline cranial base targets using expanded endonasal and transcranial approaches

OBJECTIVE

Endoscopic endonasal approaches provide an access method to the midline cranial base. To integrate these approaches into neurosurgical practice, the extent of their anatomic exposure must be compared with that provided by more traditional transcranial approaches.

METHODS

Ten fresh cadaver heads were studied. Both endonasal and transcranial approaches to the midline cranial base were performed. The midline cranial base was divided into several areas, and the relative exposure provided by each approach was described and presented in both 2-dimensional and 3-dimensional images. Limitations and advantages of each approach are discussed.

RESULTS

The endonasal approaches achieved a direct and wide exposure of the midline extracranial and intracranial cranial base anatomy. The main lateral limitations of the endonasal approaches were the optic nerves, lateral cavernous sinus, vidian nerve, internal carotid artery, abducens nerve in Dorello's canal, jugular tubercle, and hypoglossal canals. Limitations of the transcranial approaches were the neurovascular structures which lie in the operative corridor and create narrow working spaces.

CONCLUSION

The endonasal approaches achieve a direct and wide exposure of the midline cranial base bilaterally. Lateral exposure, beyond the cranial nerves and carotid artery, are challenging. Transcranial approaches are limited by the narrow corridors provided by the cranial nerves, and they do not visualize the contralateral paramedian cranial base very well. Three-dimensional endoscopes augment the spatial orientation and may improve patient safety and the learning curve for endoscopic approaches to the midline cranial base.

Extended endoscopic endonasal transsphenoidal approach to the suprasellar region: anatomic study and clinical considerations

The extended endoscopic endonasal approach to the suprasellar region was performed on 10 fresh adult cadavers to describe the anatomic landmarks and key surgical steps for safe performance of the surgical approach. The anatomic features and relationships of the sphenoidal ostia, sphenoidal sinus, and optic-carotid recess are described, as are four intradural suprasellar neurovascular structural areas, including the suprachiasmatic, subchiasmatic, retrosellar and ventricular regions. Various anatomic conditions may influence the use of the extended endoscopic endonasal approach. This approach provides a straight, midline approach to the suprasellar region and offers a multi-angled and close-up view of the relevant neurovascular structures. For clinical use, the most important surgery-related complications concern the management of operative bleeding and the prevention of postoperative cerebrospinal fluid leakage.

MICROSURGICAL AND ENDOSCOPIC ANATOMY OF THE SUPRATENTORIAL ARACHNOIDAL MEMBRANES AND CISTERNS

OBJECTIVE

A limitation of previous studies of the arachnoid cisterns and membranes is that the act of opening the sylvian and interhemispheric fissures and basal arachnoid often led to destruction of the cisternal compartments and their membranous walls. The goal of this study was to overcome this limitation by combining the surgical microscope and endoscope for the examination of the cisternal compartments and their membranous walls.

METHODS

The supratentorial cisterns were examined in 22 cadaveric brains using both the operating microscope and the endoscope.

RESULTS

There are 2 types of arachnoid membranes: outer and inner. The outer arachnoidal membrane surrounds the whole brain, and the inner membranes divide the subarachnoid space into cisterns. Twelve inner arachnoid membranes were identified in the supratentorial area: diencephalic, mesencephalic, medial carotid, intracarotid, intracrural, olfactory, medial and lateral lamina terminalis, and proximal, medial, intermediate, and lateral sylvian membranes. These membranes partially or completely separate the subarachnoid space into 9 supratentorial cisterns: sylvian, carotid, chiasmatic, lamina terminalis, pericallosal, crural, ambient, oculomotor, and interpeduncular. There is a confluent area between the carotid, interpeduncular, and crural cisterns, which frequently has no membrane separating these cisterns.

CONCLUSION

Twelve inner arachnoid membranes and 9 cisterns were identified in this study.

Extended endoscopic endonasal transsphenoidal approach for residual or recurrent craniopharyngiomas

Object

The management of recurrent or residual craniopharyngiomas remains controversial. Although possible, revision surgery is more challenging than primary surgery, and more often results in incomplete resection and an increased risk of death and complications. The extended (also called expanded) endoscopic endonasal transsphenoidal approach through the planum sphenoidale has been proposed over the past decade as an alternative surgical route for removal of various suprasellar tumors including craniopharyngiomas. In this study, the authors describe the feasibility and advantages of this technique in recurrent or symptomatic residual craniopharyngiomas.

Methods

Between January 2004 and June 2008, 22 patients underwent surgery via the extended endoscopic transsphenoidal approach for the treatment of recurrent or residual symptomatic craniopharyngiomas at either the University of Pittsburgh or the Universita degli Studi di Napoli. The lesions included 12 purely suprasellar craniopharyngiomas, 9 with both intra- and suprasellar extensions, and 1 arising from a remnant in the Meckel cave. To better evaluate the features of the extended endonasal approach for recurrent or residual craniopharyngiomas, each patient was assigned to 1 of 3 subgroups depending on the original surgical treatment: transcranial pterional route (13 patients), transphenoidal approach (3 patients; 2 microsurgically and 1 with the standard endoscopic technique), or extended endonasal endoscopic approach (6 patients).

Results

Total removal was achieved in 9 patients (40.9%), and in 8 patients (36.4%) near-total removal (defined as > 95% removal) was possible. Subtotal removal (> 70%) was attained in 4 patients (18.2%), and tumor removal was partial (< 50%) in only 1 case (4.5%). There were no deaths or major complications, including behavior changes. Postoperative CSF leaks developed in 2 patients in the transcranial subgroup, and 1 in the transsphenoidal subgroup (overall rate 13.6%), requiring early successful endoscopic revision surgery for the cranial base defect.

Conclusions

Most of the advantages of the endoscopic endonasal technique were noted during tumor dissection from the inferior aspect of the chiasm, the infundibulum, the third ventricle, and/or the retro- and parasellar areas. These benefits were best appreciated in patients who had originally undergone transcranial surgery, since in such cases the authors' endoscopic endonasal approach was a virgin route. However, the extended endoscopic endonasal technique can also be safely used in patients who originally underwent transsphenoidal surgery. The endoscopic endonasal technique should be considered as a therapeutic option in selected cases of recurrent or symptomatic residual craniopharyngiomas.

Endoscopic skull base surgery

Endoscopic skull base surgery has undergone rapid advancement in the past decade moving from pituitary surgery to suprasellar lesions and now to a myriad of lesions extending from the cribriform plate to C2 and laterally out to the infratemporal fossa and petrous apex. Evolution of several technological advances as well as advances in understanding of endoscopic anatomy and the development of surgical techniques both in resection and reconstruction have fostered this capability. Management of benign disease via endoscopic methods is largely accepted now but more data is needed before the controversy on the role of endoscopic management of malignant disease is decided. Continued advances in surgical technique, navigation systems, endoscopic imaging technology, and robotics assure continued brisk evolution in this expanding field.