Davide Mattavelli, Marco Ravanelli, Davide Lancini, Marco Ferrari, Alberto Schreiber
The transplanum–transtuberculum approach provides direct access to the suprasellar areas through the planum sphenoidale and tuberculum sellae, representing a “frontier” route that can be useful to manage lesions of both the anterior and middle midline skull base. First, this approach has been combined with the transsellar route to resect the cranial portion of suprasellar pituitary adenomas via transnasal endoscopic surgery.1–4Subsequently, its employment in the resection of meningiomas of the planum sphenoidale and/or tuberculum sellae led to consider the transplanum–transtuberculum approach an independent corridor that can be combined with other pathways according to the extent of the lesion.1,5In view of its natural trajectory toward the optic system, pituitary stalk, hypothalamus, third ventricle, and anterior cerebral arterial system, the indications for the transplanum–transtuberculum approach progressively evolved to include the management of retrochiasmatic/intraventricular craniopharyngiomas,6–11hypothalamic gliomas,12choroid plexus papillomas13and germ cell tumors14of the third ventricle, and aneurysms of the anterior cerebral circulation.15
The transplanum–transtuberculum craniectomy is bounded by the anterior sellar wall posteriorly, ethmoidal roofs and cribriform plates anteriorly, and optic canals bilaterally. The planum sphenoidale and tuberculum sellae are usually properly exposed through the sphenoid sinus with a transrostral or extended transrostral sphenoidotomy. However, the posterior ethmoid also needs to be dissected when a far-lateral exposure in the area of the optic canal is required. When addressing the skull base, special attention must be paid to the structures corresponding to each side of the craniectomy: at the posterior border, the anterosuperior intercavernous sinus runs usually parallel and in close proximity to the tuberculum sellae, which in fact represent the anterior insertion of the diaphragma sellae; at the anterior border, caution should be paid to not inadvertently injure the posterior portion of the cribriform plate on the midline and posterior ethmoidal artery laterally; at the lateral border, drilling should be carefully performed together with meticulous irrigation to avoid thermal damage of the optic nerve. Within the intracranial compartment, movements should be performed with remarkable attention to avoid damaging the pituitary stalk and optic apparatus, superior hypophyseal arteries, intracranial internal carotid arteries, and anterior cerebral vessels.
After the transplanum–transtuberculum approach, reconstruction must be performed paying attention to the adjacent intracranial structures. A multilayered technique, including fascia and/or fat tissue as inner layer to avoid compression or mechanic damage of the aforementioned intracranial structures, is typically used. The so-called gasket seal technique is based on the embedding of a rigid graft of cartilage or bone to fix the plasty to the edges of craniectomy. Given its indications, which mostly include intracranial lesions, vascularized flaps as the outer layer of the reconstruction are strongly recommended after a transplanum–transtuberculum approach.16
After completing the harvesting of the surgical corridor, the reader is suggested to explore both the infrachiasmatic and the suprachiasmatic areas with angled scopes to have a three-dimensional understanding of the anatomy and identify the structures adjacent to this region that will be directly reached with approaches illustrated in other chapters. Furthermore, in specimens with favorable anatomy, an exploration of the third ventricle through the lamina terminalis is also feasible.
Fig. 8.1 Anterior-to-posterior intracranial view of the suprasellar area. This cadaver picture shows the anatomy of the suprasellar area as seen from an anterior-to-posterior intracranial perspective. A1, precommunicating tract of the anterior cerebral artery; A2, postcommunicating tract of the anterior cerebral artery; ACP, anterior clinoid process; iICA, intracranial tract of the internal carotid artery; LTCis, lamina terminalis cistern; MCA, middle cerebral artery; OCis, optic cistern; ON, optic nerve; OpA, ophthalmic artery; PSphD, dura of the planum sphenoidale; TSeD, dura of the tuberculum sellae.Fig. 8.2 Lateral-to-medial intracranial view of the suprasellar area. This cadaver picture shows the anatomy of the suprasellar area as seen from an lateral-to-medial intracranial perspective. III, oculomotor nerve; IV, trochlear nerve; ACP, anterior clinoid process; ICLi (black dashed line), interclinoid ligament; iICA, intracranial tract of the internal carotid artery; LiM, Liliequist’s membrane; OCh, optic chiasm; OpA, ophthalmic artery; ON, optic nerve; PCP, posterior clinoid process; PSphD, dura of the planum sphenoidale; TSeD, dura of the tuberculum sellae.Fig. 8.3 Sagittal CT of the midline anterior skull base. The planum sphenoidale (PSph) is the roof of the sphenoid sinus. The tuberculum sellae (TSe) is a thickening of the bone serving as a junction between planum sphenoidale and sellar prominence (SPr). The trajectory of the transplanum–transtuberculum approach passes through the sphenoid rostrum (SpR). CR, clival recess; DoS, dorsum sellae; PPEB, perpendicular plate of the ethmoid bone; Vo, vomer.Fig. 8.4 Sagittal MRI anatomy of the suprasellar area. The lamina terminalis cistern and optic cistern are located superiorly and inferiorly to the optic chiasm (OCh), respectively, and form the suprasellar area. The optic cistern is bounded by the optic system anterosuperiorly and Liliequist membrane (LiM) posteroinferiorly and includes the pituitary stalk (PSt) and superior hypophyseal arteries. The lamina terminalis cistern is bounded by the lamina terminalis (LT) posteriorly and continues into the interhemispheric fissure anteriorly. This cisternal space includes the proximal portion of the anterior cerebral arteries (ACA). The lamina terminalis serves as anterior door toward the third ventricle (ThV). Aq, cerebral aqueduct; GaV, vein of Galen; HaC, habenular commissure; Hyp, hypophysis; InRe, infundibular recess; ORe, optic recess; PiG, pineal gland; PoCo, posterior commissure.Fig. 8.5 Coronal and sagittal MRI anatomy of the suprasellar area. The panel contains a paracoronal T1-weighted, fat-saturated, contrast-enhanced MRI (a) along with a sagittal paramedian and a paracoronal constructive interference in steady state (CISS) MRI (b, c) passing through the suprasellar area. The position of the sagittal image is depicted in the upper right image (black dotted line). The optic cistern lies cranially to the diaphragma sellae (DSe), which serves as the roof of the sellar region, and below the optic system, which is formed from posterior to anterior by the optic tract (OT), optic chiasm (OCh), and optic nerve (ON). The intracranial tract of the internal carotid artery (iICA) runs at the lateral boundary of the optic cistern and bifurcates into the precommunicating tract of the anterior cerebral artery (A1) and middle cerebral artery (MCA) just cranially to the plane passing through the optic system. White dotted lines in the upper left image depict the position of images composing ▶Fig. 8.6. III, oculomotor nerve; V1, ophthalmic nerve; VI, abducens nerve; DoS, dorsum sellae; Hyp, hypophysis; PSph, planum sphenoidale; PSt, pituitary stalk; sICA, parasellar tract of the internal carotid artery; ThV, third ventricle; TSe, tuberculum sellae.Fig. 8.6 Axial MRI anatomy of the third ventricle, lamina terminalis cistern, and optic cistern. The panel contains four axial constructive interference in steady state (CISS) MRI passing through the suprasellar area and third ventricle, from cranial (a) to caudal (d). The third ventricle (ThV) is bounded by the lamina terminalis (LT) anteriorly and by the posterior commissure (PCo) posteriorly. Inferiorly, the floor of the third ventricle is mostly formed by the mammillary bodies (MBo) and tuber cinereum (TuC). The lamina terminalis cistern lies in front of the lamina terminalis and houses the anterior cerebral artery system, which is formed by the pre- (A1) and postcommunicating tract (A2) of the vessel and by the anterior communicating artery (ACoA). The optic cistern lies below the optic system, which is formed by the optic tract (OT), optic chiasm (OCh), and optic nerve (ON), and includes the pituitary stalk (PSt). ACP, anterior clinoid process; Aq, cerebral aqueduct; iICA, intracranial tract of the internal carotid artery; MCA, middle cerebral artery; Tal, thalamus.Fig. 8.7 (a, b) Coronal CT anatomy of the planum sphenoidale and tuberculum sellae. The panel contains two coronal CT images passing through the planum sphenoidale (PSph) and tuberculum sellae (TSe). The lateral boundary of the planum sphenoidale is the optic canal (OC), while the lateral limit of the tuberculum sellae is the medial optic-carotid recess (MOCR). The middle clinoid process (MCP) lies inferiorly and medially with respect to the medial optic-carotid recess and can fuse with the apex of the anterior clinoid process (ACP) forming the carotid clinoid bony ring. The lateral optic-carotid recess (LOCR) can considerably extend within the anterior clinoid process through the optic strut (OSt), which separates the optic canal, superior orbital fissure (SOF), and the parasellar and paraclinoid tracts of the internal carotid artery. Similarly, the maxillary strut (MSt) is defined as the upper portion of the foramen rotundum (FRo), which separates the maxillary nerve from the content of the superior orbital fissure. The white dotted lines (A, B) show the position of images composing ▶Fig. 8.8. SpR, sphenoidal rostrum.Fig. 8.8 Sagittal CT and MRI anatomy of the lateral boundaries of the transplanum–transtuberculum approach. The panel contains two sagittal CT scans (a, b) and two sagittal constructive interference in steady state (CISS) MRI scans (c, d). The position of images on the right and left columns is depicted in ▶Fig. 8.7 (A and B, respectively). The lateral boundary of the tuberculum sellae is the medial optic-carotid recess (MOCR), which lies between the carotid prominence (CPr) and the optic canal (OC), thus serving as a landmark to identify the interface between the paraclinoid tracts of the internal carotid artery (pcICA) and optic nerve (ON). Similarly, the lateral optic-carotid recess (LOCR) can be used to identify the plane between the parasellar tract of the internal carotid artery (sICA) and optic canal. The olfactory tract (OlT) runs at the posterolateral corner of the planum sphenoidale (PSph). III, oculomotor nerve; ACA, anterior cerebral artery; MCP, middle clinoid process; OT, optic tract.
Endoscopic Dissection
Nasal Phase
Paraseptal sphenoidotomy.
Transrostral sphenoidotomy.
Expanded transrostral sphenoidotomy.
Vertical uncinectomy.
Anterior ethmoidectomy.
Posterior ethmoidectomy.
Superior turbinectomy.
Transethmoidal sphenoidotomy.
Middle turbinectomy.
Skull Base Phase
Step 1: Removal of the mucosa of the sphenoid sinus.
Step 2: Removal of the tuberculum sellae and planum sphenoidale.
Step 3: Incision of the periosteum of the tuberculum sellae and planum sphenoidale.
Step 4: Removal of the anterior arachnoid of the optic cistern.
Step 5: Removal of the anterior arachnoid of the lamina terminalis cistern.
Step 6: Translamina terminalis ventriculostomy.
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