Introduction

In this chapter, we present the technical nuances for performing the endoscopic endonasal transtuberculum transplanum approach in a stepwise manner using illustrations derived from dissection of the anatomic specimens. This is then supplemented with a clinical case example.

Using our own experience and recently published findings from a research study, we will also present the nuances for performing a 270-degree decompression of the optic canal (OC) and the opening of the dural sheath surrounding it, which may be required for invasion/involvement of the OC with pathologies such as tuberculum sellae meningioma. This endoscopic endonasal approach has been successfully employed for the removal of tuberculum sellae and planum sphenoidale meningiomas. The incidence of optic canal invasion (OCI) has been reported to be high with these tumors, ranging from approximately 56 to 77%, thus highlighting the need for the appreciation of the anatomy of the OC and its surrounding structures from an endonasal perspective.

The knowledge of the anatomy and the principles involved in the dural opening and exposure can also be applied for approaching suprasellar lesions such as craniopharyngioma where the dura of chiasmatic sulcus is opened to expose the suprasellar infrachiasmatic cistern and resect the lesion.

10.1 Technical Description

Endoscopic endonasal anatomic dissections is performed using rod lens endoscopes (Karl Storz, 4 mm, 18 cm, Hopkins II, 0 and 45 degrees) attached to a high-definition camera and a digital video recorder system. Heads are positioned supine on the dissection table with a Mayfield head holder being used to maintain a neutral position.

An endoscopic endonasal approach to the sella and tuberculum sellae region involves a wide bilateral sphenoidotomy, posterior ethmoidectomy, and posterior septectomy ( Fig. 10.1 ). The intrasphenoidal septations are thinned down using a drill while keeping in mind that these septations can lead one off the midline to the paraclival or clinoidal carotid artery. Bone overlying the sella and the chiasmatic sulcus is eggshelled using a coarse diamond 4-mm burr ( Fig. 10.2 ).

The thinned-down bone between the limbus dura and the tubercular strut is gently dissected off while maintaining the integrity of the dura. Standard endonasal transsphenoidal landmarks can again be appreciated ( Fig. 10.3 ). The removal of the bone at this stage clearly shows the thickened dural fold (limbus dura) overlying the limbus sphenoidale. The tuberculum strut is carefully thinned down prior to its subsequent removal ( Fig. 10.4 ). Lateral end of this strut corresponds to the medial opticocarotid recess which marks the transition between the paraclinoidal carotid and the supraclinoidal carotid artery. At this stage, location of the superior intercavernous sinus can be seen. The anatomic relationships from caudal to rostral (relevant to this approach) are sella, diaphragm, superior intercavernous sinus, tuberculum, chiasmatic sulcus, limbus dura, and finally the dura of the planum (not exposed here) ( Fig. 10.5 ). The next step represents further removal of the bone to expose the planum dura. The bone overlying the OC along its medial aspect and the roof can be seen. Bone overlying the clinoidal carotid artery is thinned down and then carefully dissected off ( Fig. 10.6 ).

Fig. 10.7 shows relevant anatomy of the OC and the technique for maximal endoscopic endonasal OC decompression.

Related posts:

Chapter 9 Transcribriform Approach Chapter 12 Endoscopic Sellar Approach Chapter 11 Suprasellar Approach to the Third Ventricle Chapter 15 Transorbital Neuroendoscopic Approach Chapter 13 Cavernous Sinus Approach Chapter 14 Endonasal Endoscopic–Assisted Intraorbital Approach

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