endoscopic endonasal cavernous sinus surgery: an anatomic study

ANATOMIC REPORTS

Endoscopic Endonasal Cavernous Sinus Surgery:An Anatomic Study

Alessandra Alfieri, M.D., Hae-Dong Jho, M.D., Ph.D.Center for Minimally Invasive Innovative Microneurosurgery (H-DJ), Department of

Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh,Pennsylvania, and Department of Neurosurgery (AA), “Federico II” University of

Naples School of Medicine, Naples, Italy

OBJECTIVE: The endoscopic surgical anatomy of the cavernous sinus was studied to establish an anatomic basis forendoscopic endonasal cavernous sinus surgery.

METHODS: Five adult cadaveric heads were studied with 0-, 30-, and 70-degree 4-mm rod-lens endoscopes. The posterior wallof the sphenoidal sinus was approached via a paraseptal, middle turbinectomy, or middle meatal approach.

RESULTS: The posterior bony wall of the sphenoidal sinus is subdivided into five vertical compartments: midline, bilateralparamedian, and bilateral lateral. The midline vertical compartment consists of the planum sphenoidale, tuberculumsellae, sella, and clival indentation. The paramedian vertical compartment is composed of the medial third of the opticcanal and the carotid artery protuberance. The lateral vertical compartment contains four bony protuberances (optic,cavernous sinus apex, maxillary, and mandibular) and three depressions (carotico-optic, ophthalmomaxillary [V1–V2],and maxillomandibular [V2–V3]). The three depressions form anatomic triangles at the lateral vertical compartment:the optic strut triangle, which is bordered by the optic nerve, carotid artery, and oculomotor nerve (IIIrd cranialnerve); the V1–V2 triangle; and the V2–V3 triangle. The internal carotid artery at the posterior wall of the sphenoidalsinus can be subdivided into two main segments: the parasellar and the paraclival. The vidian canal is a landmark thatleads to the foramen lacerum, the mandibular nerve, and the pterygopalatine fossa.

CONCLUSION: Endoscopic anatomy of the cavernous sinus has been studied via an endonasal route in cadavericspecimens to provide an anatomic basis for endoscopic endonasal cavernous sinus surgery.(Neurosurgery 48:827–837, 2001)

Key words: Cavernous sinus, Endoscopic transsphenoidal surgery, Internal carotid artery, Pituitary adenoma, Vidian nerve

Since transsphenoidal surgery was revived with theadoption of the operating microscope, detailed anatomicstudies have been performed to delineate the neurovas-

cular relationship at the sphenoidal sinus (10, 21, 24–26).Despite the complexity of this relationship at the posteriorwall of the sphenoidal sinus, microscopic transsphenoidalsurgery has been established as a safe, straightforward neu-rosurgical procedure with minimal morbidity, owing to lim-ited midline surgical exposure at the anterior wall of the sella.Although microscopic transsphenoidal surgery has been re-ported for the surgical removal of cavernous sinus pathology,it has been limited to the surgical treatment of sellar andsuprasellar pathology because of its narrow surgical expo-sure, which precludes surgical maneuvering in the cavernoussinus under direct visualization (9, 20, 28).

Beginning in 1993, when the senior author (HDJ) developedendoscopic endonasal transsphenoidal surgery, interest insurgically treating pathology in the cavernous sinus increased

when it was noted that the optical characteristics of an endo-scope provide much wider and more panoramic images of theposterior wall of the sphenoidal sinus than does the operatingmicroscope (3, 4, 11–18). The complex neurovascular anatomythat is revealed at the posterior wall in cadaveric studies isdirectly demonstrated when an endoscope is introduced intothe sphenoidal sinus. A preliminary study of the endoscopicanatomy at the cavernous sinus has been conducted, andsurgical treatment for pathology in the cavernous sinus hasbeen carried out (15).

Despite an existing preliminary endoscopic anatomic studyof the cavernous sinus, a more detailed study became imper-ative to accommodate for intrinsic optical distortion of theanatomy related to endoscopic optics, two-dimensional (2-D)images, and image characteristics related to varied lens angu-lations of the endoscope. The aspects of shape, size, andthree-dimensional (3-D) relationships with endoscopic anat-omy have been found to be quite different from those of

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microscopic anatomy. When using an endoscope, a surgeonmay have difficulty in correlating distorted 2-D cavernoussinus anatomy to its 3-D relationship with surrounding anat-omy (1). In addition, an endoscopic transsphenoidal view ofthe cavernous sinus discloses an anteroinferior perspective ofthe anatomic structures in such a unique manner that it isdifficult to interpret based solely on the knowledge and ex-perience gained through transcranial lateral craniotomy ap-proaches. In this report, we describe an endoscopic perspec-tive of the surgical anatomy at the cavernous sinus to providethe anatomic basis needed to enable neurosurgeons to per-form endoscopic endonasal transsphenoidal procedures oncavernous sinus pathology.

MATERIALS AND METHODS

Ten cavernous sinuses in five adult cadaveric heads werestudied. The arteries were injected with red latex. The veinswere not injected, because the aim was not to study cavernoussinus venous anatomy. Rod-lens endoscopes, 4 mm in diam-eter and 18-cm in length, with 0-, 30-, and 70-degree lenseswere used. A Neuroview system 500 (Integra NeuroSciences,Plainsboro, NJ) with a three-chip digitally enhanced videocamera enabled video images of the endoscopic anatomy to berecorded during the study. Digital pictures were reproducedby coupling the video images with a computer videocapturesystem. This endoscopic study was performed through threedifferent endonasal surgical routes via one nostril. The para-septal, middle meatal, or middle turbinectomy approach was

used. The surgical trajectory for the paraseptal approach wasmade between the nasal septum and the middle turbinate.The trajectory for the middle meatal approach was madebetween the middle turbinate and the lateral wall of the nasalcavity. The middle turbinectomy approach was made by re-moving the caudal half of the middle turbinate. The surgicalcorridor of the middle turbinectomy approach was larger thanthat of the other two approaches. An anterior sphenoidotomywas then performed to expose the posterior wall of the sphe-noidal sinus.

RESULTS

The sphenoidal sinus posterior wall

Through an anterior sphenoidotomy, the posterior wall ofthe sphenoidal sinus can be visualized with a wide panoramicview when a 0-degree endoscope is used. To expose the lateralrecess at the posterior wall of the sphenoidal sinus, 30- and70-degree angled-lens endoscopes are used. All utilized ca-daver specimens had well-pneumatized sphenoidal sinuses.A consistent landmark that leads to the orientation of thesurrounding surgical anatomy is the clival indentation. Thisbony depression is bordered by the sellar floor superiorly andthe carotid artery protuberances laterally. The sella is at thecenter of the sphenoidal sinus posterior wall (Fig. 1, A and B).The bony anatomy can be subdivided into five vertical com-partments: midline, bilateral paramedian, and bilateral lateral(Fig. 1C).

FIGURE 1. A 0-degree-lens endo-scopic view of the bony anatomy ofthe posterior wall of the sphenoidalsinus: sella (s), clival indentation (c),planum sphenoidale (ps), optic canal(oc), carotico-optic recess or opticstrut (os), carotid protuberance (cp),maxillary protuberance (mp), and fora-men lacerum (fl) (A and B). The poste-rior wall of the sphenoidal sinus canbe subdivided into five vertical com-partments by two lines drawn verti-cally on either side along the medialand lateral margins of the carotid pro-tuberance: the midline compartment(mc); the paramedian compartments,right and left (pmc); and the lateralcompartments, right and left (lc) (C).The clival indentation (c), the sella (s),and the planum sphenoidale (ps)

belong to the midline compartment; the paraclival ICA (pc ICA), the parasellar ICA (ps ICA), and the medial optic canal (oc)belong to the paramedian compartments; and V2 (mx p), the cavernous sinus apex (CS-a), the carotico-optic recess or opticstrut (os), and the lateral optic canal belong to the lateral compartments (D).

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Once surgical orientation is established by identification ofthe clival indentation, the bony anatomy at the midline ver-tical compartment is easily defined rostrally by the protrudedsella, the tuberculum sellae, and the planum sphenoidale (inthat order). A mild, narrow central bulge just superior to thesella represents the tuberculum sellae, which anchors thechiasmatic sulcus intracranially and is bordered by the opticcanals laterally. By rotating an angled-lens endoscope anddirecting the lens either rostrally or caudally, a more projectedview of the anatomy can be demonstrated; optical imagedistortion will be relative, depending on the degree of lensangulation.

At the paramedian vertical compartment, carotid protuber-ances are viewed on either side. These protuberances coveringthe internal carotid artery (ICA) can be subdivided into theparaclival protuberance caudally and the parasellar protuber-ance rostrally. The paraclival ICA protuberance is readilyrecognizable at the lateral wall of the clival indentation. At itsinferior end is the exocranial part of the foramen lacerum.This part of the so-called “foramen lacerum medium” is usu-ally covered by fibrocartilaginous tissue. However, fibrocar-tilaginous tissue is sometimes absent; in one specimen, thiscovering was not present bilaterally. When the paraclivalsegment reaches the level of the sellar floor rostrally, it be-comes the parasellar carotid protuberance. The bony coveringof this protuberance broadens wider than the paraclival pro-tuberance and mildly protrudes farther than the anterior wallof the sella. The parasellar protuberance covers the C-shapedserpentine turn of the ICA, but it is not as distinctly recogniz-able by the external configuration of the bony coverage. Themedial third of the optic canal is in the paramedian compart-ment. Rostral to this medial part of the optic canal is thelateral portion of the planum sphenoidale (Fig. 1D).

The lateral vertical compartment of the posterior wall of thesphenoidal sinus is well defined, with four bony protrusionsand three bony depressions. From rostral to caudal, the fourbony protuberances are the optic canal, the cavernous sinusapex, the trigeminal maxillary division (V2), and the trigem-inal mandibular division (V3). The three prominences inferiorto the optic nerve resemble the shape of the trigeminal divi-sions. The trigeminal mandibular protuberance is not easilynoticeable unless the sphenoidal sinus is well pneumatized.The three bony depressions are the carotico-optic recess, thedepression between the cavernous sinus apex and V2, andthe depression between V2 and V3 (Fig. 2). When the sphe-noidal sinus is septated in a complex manner or is not wellpneumatized, these bony demarcations may not be as distinctas described above.

The carotico-optic recess is a consistent bony depressionbordering the optic nerve rostrally and the carotid arterymedially. It is composed of the optic strut, which constitutesthe medial base of the anterior clinoid process. The carotico-optic recess is shaped in a triangular configuration, with itsnarrow base facing the parasellar carotid protuberance medi-ally and its sharp apex pointing laterally. When bone is re-moved, a triangle that we named the “optic strut triangle” canbe seen to be composed of the optic nerve superiorly, the

oculomotor nerve inferiorly, and the carotid artery medially.The optic nerve extends toward the orbital apex.

The inferior bank at the carotico-optic recess swells progres-sively in a cone shape (the “cavernous sinus apex” protuber-ance), with its base resting at the parasellar carotid protuberancemedially and its apex becoming the superior orbital fissurelaterally. The third bony protuberance (the “maxillary” pro-tuberance), which is inferior to the cavernous sinus apexprotuberance, is the bony covering of the maxillary trigeminalnerve that passes through the foramen rotundum. The fourthbony prominence, which is inferior to the maxillary protuber-ance, is the “mandibular” protuberance that covers the pass-ing mandibular trigeminal nerve.

The depression between the cavernous sinus apex and theV2 protuberances produces a triangular shape that we call the“V1–V2 triangle.” When the bone and periosteum are re-moved, the V1–V2 triangle, with its apex pointing medially, isbordered by V1 superiorly and V2 inferiorly. The narrow baseof this triangle separates the superior orbital fissure superi-orly from the foramen rotundum inferiorly. This triangleleads to the medial temporal lobe when the dura mater is

FIGURE 2. A 30-degree-lens endoscopic view of the lateralvertical compartment. The lens is turned toward the left sideof the posterior wall of the sphenoidal sinus (A). The threebony depressions are the carotico-optic recess, which is bor-dered by the optic nerve (op) superiorly, the ICA inferomedi-ally, and the oculomotor nerve inferolaterally; the depressionbetween the cavernous sinus apex (CS-a) and V2 (mx p); andthe depression between V2 (mx p) and V3 (md p). Thosedepressions form triangles: the optic strut triangle is drawnin red, the V1–V2 triangle is in blue-green, and the V2–V3triangle is in dark blue (B).

Endoscopic Cavernous Sinus Anatomy 829


opened; it can be a site of spontaneous cerebrospinal fluidleakage when the dura mater develops a defect. The depres-sion between the V2 and V3 protuberances forms anothertriangular configuration that we call the “V2–V3 triangle.”When the bone is removed, the V2 nerve forms a superior armand the V3 nerve forms an inferior arm of the V2–V3 triangle.When the dura mater is opened at this depression, the infero-medial temporal lobe is visualized. This triangle also can be asite of spontaneous cerebrospinal fluid leakage when the duramater develops a defect.

The vidian canal is identifiable between the lacerum seg-ment of the ICA posteromedially and the pterygopalatinefossa anterolaterally at the caudal portion of the lateral verti-cal compartment (Fig. 3). The greater superficial petrosalnerve joins the deep petrosal nerve to become the vidiannerve at the cartilaginous portion of the foramen lacerum. Thevidian nerve exits the cranium through the vidian canal,which is located anteriorly to the foramen lacerum, and headstoward the pterygopalatine fossa. The nerve passes anterolat-erally across V3. The foramen lacerum is located medially andsuperiorly to the vidian canal. The Eustachian tube is locatedinferiorly to the vidian canal. The vidian nerve reaches thepterygopalatine fossa to join the sphenopalatine ganglion.This nerve is an important landmark leading to the foramenlacerum, mandibular nerve, foramen ovale, pterygopalatinefossa, and Eustachian tube.

The medial wall of the cavernous sinus

When the bone of the posterior wall of the sphenoidal sinusis removed, the periosteum covers all of the surroundinganatomy that is located underneath. The periosteum consti-tutes the outer layer of the dura mater at the anterior dural

wall of the sella; it separates from the dura propria of the sellaat the lateral edge and runs continuously laterally to cover thelateral anatomy. The periosteum covers the ICA that is ex-posed toward the sphenoidal sinus all along its intracavern-ous course. The inner layer of the dura mater at the sella (thedura propria) continues to be the lateral wall of the sella,which is the medial wall of the cavernous sinus along themedial aspect of the C-shaped parasellar segment of the ICA.Despite controversies regarding the presence of the medialwall, we observed that the medial wall of the cavernous sinusis formed by the dura propria that covers the pituitary gland(5, 19). The lateral and posterior aspects of the cavernous sinusICA are exposed freely in the cavernous sinus cavity (Fig. 4).When a 30- or 70-degree endoscope is directed toward themedial cavernous sinus at the inner aspect of the C-shapedICA, after partial removal or contralateral displacement of thepituitary gland, the medial wall of the cavernous sinus isdirectly visualized. When this wall is opened at the medialaspect of the C-shaped parasellar segment of the ICA, theposterior and upper parts of the cavernous sinus are entered.The carotid artery itself rests in the major portion of thecavernous sinus so that the entire sinus cavity will be dis-closed only when the parasellar carotid artery is mobilizedmedially by release of the clinoidal dural rings.

The cavernous sinus carotid artery

Although several different classifications describe the seg-ments of the ICA, they are not suitable for the endoscopicendonasal perspective. When the posterior wall of the sphe-noidal sinus is visualized, two distinct divisions of the cav-ernous sinus ICA (the paraclival caudally and the parasellarICA rostrally) are readily recognizable by their bony protu-berances, as described earlier (Fig. 5, A–C).

The paraclival ICA segment can befurther subdivided into two parts: thelacerum segment caudally (the extra-cavernous sinus) and the trigeminalsegment rostrally (the intracavernoussinus). When the mucosa of the sphe-noidal sinus is removed, the lacerumsegment of the ICA can be identified asa bare artery if fibrocartilage is absent.A consistent landmark leading to thelacerum segment is the vidian canal,which is located inferolaterally to the

FIGURE 3. A 30-degree-lens endo-scopic view directed laterally to theright. At the caudal portion of the lat-eral vertical compartment in the right-sided sphenoidal sinus, the foramenlacerum (fl), V2 prominence (mx p),and vidian canal (vc) are demonstrated(A). When bone is removed, the ICA,V2, and vidian nerve (vn) are exposed(B). When the vidian nerve is followedlaterally, the pterygopalatine fossa (pf)can be reached (C and D).

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foramen lacerum. The ICA does not enter the foramenlacerum but courses dorsally to the fibrocartilaginous tissue.The lacerum segment of the ICA is bordered by the vidiannerve canal inferolaterally and the origin of V3 superolater-ally. When the ICA passes the lacerum area, it enters thecavernous sinus to become the trigeminal segment of thecavernous ICA. The petrolingual ligament, which inserts tothe roof of the foramen lacerum, is the inferior limit of thecavernous sinus; however, this ligament is located posteriorlyto the ICA so that it is not recognizable through this endo-scopic view. This trigeminal segment of the ICA is readilyrecognizable as the carotid bony protuberance lateral to theclival indentation. Posterior to this segment of the carotidartery is the gasserian ganglion. Lateral to it are the trigeminaldivisions, so it is named the trigeminal segment of the para-clival cavernous sinus ICA (Fig. 5D).

The parasellar segment of the ICA is C-shaped, with theconvexity of the “C” facing anterolaterally when it is viewedfrom the medial aspect. It is subdivided into four parts in acaudal-to-rostral order: the “hidden segment,” the inferiorhorizontal segment, the anterior vertical segment, and thesuperior horizontal segment. The hidden segment is the pos-

terior bend of the ICA and is located posteriorly to the sellarfloor. It cannot readily be seen by this endoscopic anteroinfe-rior approach, thus it is called the “hidden segment.” Theinferior horizontal segment is a relatively long segment of thecavernous ICA; however, it may be mistaken for being veryshort when viewed via the endoscopic anterior approach. Thissegment is located anterior to the hidden segment, at the levelof the sellar floor. The anterior vertical segment is located justlateral to the anterior wall of the sella and constitutes the mostconvex portion of the C-shaped ICA. The superior horizontalsegment of the ICA is composed of the clinoidal segment ofthe ICA as well as the subarachnoid portion. The clinoidalsegment of the ICA starts at the inferior margin of the opticstrut triangle, where the proximal dural ring is located, andends at the superior margin of the optic strut, where the distaldural ring is located. When the middle clinoid is present, it islocated medial to the parasellar ICA. When the middle clinoidis found, the ICA is located between the middle clinoid me-dially and the optic strut triangle laterally. The posteriorclinoid is demonstrable posteriorly through the rostral junc-ture of the pituitary gland and parasellar ICA. Although theupper limit of the cavernous sinus is the distal dural ring, thesubarachnoid portion of the ICA is important for endoscopiccavernous sinus surgery. The reason for its importance is thatan endoscopic surgical procedure can be performed throughthe inner aspect of the C-shaped carotid siphon, which in-cludes the subarachnoid portion of the ICA. When the duralring is opened, the subarachnoid portion of the ICA is clearlyexposed. This “shrimp-” or C-shaped parasellar cavernoussinus ICA can be seen as a flattened, straight tubular shapewhen it is viewed under a 0-degree-lens endoscope through astraight anterior surgical approach such as the middle meatalapproach. However, the C-shaped configuration becomesparticularly evident when an angled-lens endoscope is ap-plied through a mildly oblique entry such as a contralateralparaseptal or a middle turbinectomy approach (Fig. 5D). Theintracavernous ICA extends from the trigeminal segment tothe clinoidal segment.

The inferior hypophyseal artery is identified inferolaterallyto the pituitary gland (Fig. 6A). If the ICA is displaced later-ally, the meningohypophyseal artery and its branches of thedorsal meningeal, inferior hypophyseal, and tentorial arteriesare identifiable (Fig. 6B). The inferolateral trunk (Fig. 6C), withits branches to the cavernous sinus cranial nerves, is easilydetected laterally to the ICA in the lateral wall of the cavern-ous sinus. Its origin can be seen by medial dislocation of theparasellar segment of the ICA. The inferolateral trunk sup-plies all of the cavernous sinus nerves, with the exception ofthe proximal segment of the VIth cranial nerve, which re-ceives blood from the tentorial artery.

The lateral wall of the cavernous sinusWhen the periosteum of the inferior wall of the cavernous

sinus is removed, the lateral wall of the cavernous sinus isexposed. The parasellar segment of the ICA overlaps with themiddle third of the cavernous sinus (Fig. 7A). Posterior to it is theinner aspect of the ICA. The oculomotor and trochlear nerves arelocated inside the C-shaped ICA. The oculomotor nerve first

FIGURE 4. A and B, 0-degree-lens endoscopic views of thedura mater of the anterior wall of the sella. The dura materis composed of the outer layer of periosteum and the innerlayer of dura propria (A). The periosteum covers only theanterior wall of the sella. When the dura mater of the sellaturns posteriorly to become the medial wall of the cavernoussinus (d), the dura propria separates from the periosteum (p),which runs laterally to cover the ICA (B). When the medialwall of the cavernous sinus, the dura propria, is opened, theC-shaped carotid artery is exposed.



runs under the posterior clinoid, which is located at the rostraljuncture between the pituitary gland and clinoidal segment ofthe ICA. It passes along the middle of the C-shaped ICA andthen crosses behind the rostral anterior vertical segment of theICA to enter into the cavernous sinus apex. At the apex, it runsalong the inferior margin of the optic strut triangle until itreaches the superior orbital fissure. The trochlear nerve runsparallel and just inferior to the oculomotor nerve. When theparasellar ICA is displaced medially, the oculomotor nerve, thetrochlear nerve, and the proximal and distal dural ring can beseen (Fig. 7B). The gasserian ganglion is located just behind theupper portion of the paraclival cavernous sinus ICA. Lateral to

this ICA segment, the trigeminal ganglion forms the three divi-sions of the trigeminal nerve. The ophthalmic division runsobliquely in a rostral and anterior direction toward the cavern-ous sinus apex. Starting at the lateral and inferior edges of theparasellar segment of the ICA, it approaches the oculomotor andtrochlear nerves at the superior orbital fissure (Fig. 7C). Theabducens nerve passes through Dorello’s canal, which is locatedobliquely behind the rostral portion of the paraclival ICA, ap-proximately 5 to 10 mm inferior to the sellar floor at the medialaspect of the ICA and a few millimeters below the sellar floor atthe lateral aspect of the ICA. The abducens nerve heads towardthe orbital apex, running its course inferiorly to the medial

FIGURE 5. A, view under a 0-degree-lens endoscope; B–D, views under a30-degree-lens endoscope directedlaterally to the left. The ICA in thecavernous sinus can be subdividedinto two portions according to thebony coverage, which is notablethrough this endoscopic approach: theparaclival ICA (pc ICA), which is lat-eral to the clival indentation, and theparasellar ICA (ps ICA), which is lat-eral to the sella (A). When bone andpart of the periosteum lateral to thesella are removed, the ICA coveredwith the periosteum is disclosed (B).When the periosteum is removed fur-ther laterally, the entire ICA at thecavernous sinus is exposed (C). Theparaclival ICA can be subdivided intothe lacerum segment (l s) (the extra-cavernous sinus) and the trigeminalsegment (t s) (the intracavernoussinus). The parasellar ICA forms aC-shaped curvature that can be

viewed through an endonasal endoscopic projection. It can be subdivided into four segments: the hidden segment (h s), theinferior horizontal segment (ih s), the anterior vertical segment (av s), and the superior horizontal segment (D). The superiorhorizontal segment consists of the clinoidal segment (c s) as well as the intracranial subarachnoid segment (s s).

FIGURE 6. A, view under a 30-degree-lens endoscope directed cephalad; B and C, views under a 30-degree-lens endoscopedirected laterally to the left. The bilateral inferior hypophyseal arteries (arrows), which arise from the inferior horizontal seg-ment, are demonstrated (A). When the left parasellar ICA is displaced laterally, the branches of the meningohypophysealartery, such as the tentorial artery (T a), the inferior hypophyseal artery (Hy a), and the dorsal meningeal artery (Dm a) arevisualized (B). s, sella. When the left parasellar ICA is displaced medially, the inferolateral trunk (Il T) is demonstrated (C).III, IV, V 1, and VI, cranial nerves.

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aspect of the ophthalmic trigeminal nerve. The abducens nervecan easily be seen at the inferolateral edge of the inferior hori-zontal segment of the parasellar ICA, when the periosteum ofthe inferior wall of the cavernous sinus is opened. The abducensnerve runs through the venous sinus cavity. However, the othercranial nerves are covered with the thin inner membrane of thelateral wall of the cavernous sinus.

The superior orbital fissure

The second bony protuberance at the posterior wall of thesphenoidal sinus (the cavernous sinus apex) continues ante-riorly to become the superior orbital fissure. The inferomedialaspect of the superior orbital fissure can be seen clearly and isapproached via the endoscopic approach (Fig. 7, A and B). Theoptic strut triangle is a landmark leading to the superiororbital fissure. A 30- or 70-degree angled-lens endoscope isrequired to widely visualize this region.

DISCUSSION

The cavernous sinus, named a “veritable jewel box” byParkinson (23) for its complexity and its anatomic contents,continues to be the object of study and dispute. Among manyanatomic studies of the cavernous sinus (6–8, 10, 20–23, 25, 26,29, 30), only a few were conducted as anatomic guidance forthe transsphenoidal pituitary approach (10, 21, 25). From thebeginning of the senior author’s endoscopic experience (13,17), it has been noted that an important advantage of theendoscopic technique is the wider surgical field as comparedwith the classic microscopic technique (3, 4, 11–18). The en-doscope is, in fact, introduced within the anatomy. Increasedsurgical experience with the use of various angled-lens endo-scopes has confirmed that cavernous sinus pathology can beaccessed easily by using the endoscopic technique. In addi-tion, the transsphenoidal approach, an approach to the medialwall of the cavernous sinus, carries intrinsic advantages inavoiding cranial nerve dissection. In fact, because the cavern-ous sinus cranial nerves are located at the lateral wall of thecavernous sinus, the lateral transcranial approach must carryout nerve dissection while the surgical approach is being

made toward the pathology. Despite previous studies of thesurgical anatomy conducted for transsphenoidal surgery, animportant issue in endoscopic surgery has been “distorted”anatomy. This issue is related to the intrinsic optical charac-teristics of a rod-lens endoscope (1), as well as optical elon-gation induced by an angled-lens endoscope. Because of theoptical characteristics of the endoscope, we have conductedthis anatomic study in the cavernous sinus to construct anendoscopic anatomic foundation.

An endoscopic image can provide more information in asingle image because of its panoramic view into which all sur-rounding anatomy is compressed. This optical distortion is notuniform, because the periphery is more compressed than thecentral area. The compressed peripheral anatomy appears to besignificantly smaller than the actual size. This “barrel-type” ofspatial distortion is further accentuated eccentrically when anangled lens is introduced. The distortion can create difficulty inrecognizing real anatomy because it alters the spatial relation-ships, morphology, and sizes of objects. In addition, the directlight projected from the tip of an endoscope produces imagesthat interfere with proper depth perception (2-D vision) becauseof the absence of shadows. This artificial image distortion ismore evident when the image is magnified by the close approx-imation of the endoscope tip to the target, along with increasedlight intensity. For instance, these changes are particularly evi-dent with the shape of the ICA, which appears flattened andsimilar to two “shrimps” or two Cs that are placed laterally tothe hypophysis. This distorted anatomy is further changed whenan angled lens is applied (Fig. 8). These variously distortedimages can be confusing when the surgeon is not familiar withthe manner in which the anatomy can be affected by this opticaldistortion. The contracted image of the cavernous sinus ICA in a2-D endoscopic view can be especially confusing with regard tosurgical orientation of the true 3-D anatomy. A 0-degree-lensendoscope allows better surgical orientation and task perfor-mance (Fig. 8, A and B). Nevertheless, the angled-lens endo-scopes can demonstrate the lateral anatomy well (Fig. 8D). Al-though a 30- or 70-degree-lens endoscope offers a wide view ofthe cavernous sinus structures, a 0-degree-lens endoscope stillprovides adequate visualization when the endoscope is inserted

FIGURE 7. A–C, 30-degree-lens endoscopic views directed laterally to the left. Once the periosteum is removed at the cav-ernous sinus apex, cranial nerves III, IV, V-1, VI, and the superior orbital fissure (sof) are exposed laterally to the parasellarICA (A). When the parasellar ICA is displaced medially, the cranial nerves overlaid by the ICA are fully visualized (B). Theentire lateral wall of the cavernous sinus is visualized in this picture. Lateral to the ICA, cranial nerves III, IV, V-1, VI, andV-2 are well demonstrated (C). Oph a, ophthalmic artery; on, optic nerve; os, optic strut.



through the contralateral nostril via either a paraseptal or amiddle turbinectomy approach (Fig. 8).

The sphenoidal sinus is a window to the anterior, middle, andposterior cranial fossae. When this wide window to the cranialbase is surgically approached using an endoscopic endonasaltechnique, precise surgical landmarks are essential for a success-ful operation. These landmarks allow the surgeon to recognizeand approach the surgical target without confusion. The naso-pharynx, middle turbinate, and inferior turbinate are some of thelandmarks in the nasal cavity. Once the sphenoidal sinus isentered, the anatomic structures of the sphenoidal sinus poste-rior wall, which are described above, under Results, are theunique landmarks that will guide the surgeon to the surgicaltarget. In an endoscopic anatomic point of view, the posteriorwall of the sphenoidal sinus is divided into five vertical com-partments: the midline, bilateral paramedian, and bilateral lat-eral. The bony anatomy of the midline vertical compartment isrelatively simple and distinct with the sella at the center. Theparamedian vertical compartment is readily recognizable by thecarotid protuberances lateral to the clival indentation caudallyand by the carotico-optic recesses rostrally. These external bonylandmarks will guide the surgeon to the area of interest as longas the surgeon is familiar with the aforementioned endoscopi-cally distorted surgical anatomy. However, a well-pneumatized

sphenoidal sinus, such as the sellar type, is a prerequisite forsuch landmarks. Image-guided frameless stereotaxy may assistthe surgeon in cases involving a presellar or conchal type ofsphenoidal sinus.

Many different classifications of the ICA segments have beensuggested based on angiographic or lateral craniotomy points ofview, but none considers an endoscopic transsphenoidal per-spective. Although the classification introduced recently byBouthillier et al. (2) is most agreeable, it considers the cavernoussinus carotid artery simply as a single segment, the “C4.” Furthersubdivision is required in anatomic guidance for endoscopictranssphenoidal surgery. We subdivided the C4 segment ofBouthillier’s classification into four segments: the trigeminal,hidden, inferior horizontal, and anterior vertical segments. How-ever, their clinoidal segment (“C5”) of the ICA still belongsanatomically to the cavernous sinus ICA (27).

Inoue et al. (10) subdivided the intracavernous ICA into fiveparts: the posterior vertical segment, posterior bend, horizontalsegment, anterior bend, and anterior vertical segment. However,their subdivision is based on the anatomy of the ICA as viewedthrough a lateral craniotomy window or lateral projection. Intheir subdivision, the posterior vertical segment is equivalent tothe trigeminal segment of the paraclival ICA in our classification.When the cavernous sinus ICA is viewed by using the trans-

sphenoidal endoscopic approach we de-scribe here, the posterior bend (the hid-den segment) is not readily recognizableand the horizontal segment is seen erro-neously as being very short. The hori-zontal, anterior bend, anterior vertical,and clinoidal segments of the ICA areseen as a single C-shaped unit in ourendoscopic exposure, because of the flat-tened shape. This inferomedial perspec-tive, along with barrel-type endoscopicdistortion and 2-D view, makes it diffi-cult to determine the true shape of theparasellar segment of the ICA if the sur-geon is not familiar with the actual anat-omy and the endoscopic distortion. Thisis particularly true with regard to theposterior bend and the horizontal seg-

FIGURE 8. The view with the endo-scope provides optically distortedanatomy. A 0-degree-lens endoscopedemonstrates the bilateral ICAs andthe optic system with minimal distor-tion (A and B). A 30-degree-lensendoscope-directed cephalad demon-strates increased optical distortion (C).A 30-degree-lens endoscopic viewwhen the endoscope is directed cau-dally and focuses on the left-sided cav-ernous sinus (D). Views by a70-degree-lens endoscope whendirected cephalad (E) and caudally (F)increase optical distortion.

834 Alfieri and Jho


ment described by Inoue et al. In fact, we call the posterior bendthe “hidden segment” because it is not seen and because thehorizontal segment is not readily recognizable through an endo-nasal endoscopic view.

When an endoscopic transsphenoidal approach is made, theICA can be quickly recognized by its bony cover when it isdivided into the paraclival and parasellar segments. The para-clival segment is in the lateral bony bank of the clival indenta-tion, and the parasellar segment is located lateral to the sella.When the bony cover is removed, the paraclival segment issubdivided into the trigeminal segment in the cavernous sinusand the lacerum segment, which is located inferior to the cav-ernous sinus venous cavity. The lacerum segment is importantfor exposure of the ICA because it can be traced by following thevidian nerve canal. When the parasellar segment is exposed, theICA discloses itself as a C-shaped loop. When the carotid ringsand diaphragma sellae are opened, this arterial loop is consti-tuted by the inferior horizontal segment, anterior vertical seg-ment, and superior horizontal segment, which consists of theclinoidal segment as well as the subarachnoid portion of theICA. This was the reason behind the naming of the inferiorhorizontal segment that forms the inferior limb of the “C” to thehorizontal segment of the cavernous sinus carotid artery. Ourdescription of the ICA is primarily for endoscopic endonasalsurgery because it helps the surgeon, by using bony landmarks,to quickly identify the different segments of the ICA beforeopening the bone of the sphenoidal sinus.

The lateral wall of the cavernous sinus cannot be exposedcompletely without medial mobilization of the ICA when thecavernous sinus is approached via an endoscopic endonasalroute. The posterosuperior cavernous sinus can be ap-proached inside the “C” of the parasellar ICA. The cavernoussinus apex can be approached anterolaterally to the rostralparaclival and parasellar ICA. The cavernous sinus ICA lies atthe remaining portion of the cavernous sinus. Two-thirds ofthe gasserian ganglion is covered by the paraclival segmentsof the ICA, and only the lateral edge of the gasserian ganglioncan be seen lateral to it when the dura is opened.

In this cadaveric study, we have demonstrated the endoscopicanatomy of the cavernous sinus and its vicinity in an inferome-dial endoscopic perspective. The presence of swellings and de-pressions that outline precise anatomic structures have enabledus to establish important landmarks that are very helpful inobtaining correct orientation. A familiarity with these key ana-tomic points and an awareness of the endoscopic barrel-typedistortion, which is more evident with angled lenses, is manda-tory for the development of the ability to perform an endoscopicsurgical technique to treat pathology in the cavernous sinus.

ACKNOWLEDGMENTS

We thank Prof. Guido Rossi, Headmaster of the “FedericoII” University School of Naples, Naples, Italy, and Presidentof the “Leonardo di Capua” Association, and members of the“Leonardo di Capua” Association for financial assistance toAA to conduct the research program. We are also grateful toDr. Paolo Cappabianca and Prof. Enrico de Divitiis, of theDepartment of Neurosurgery, “Federico II” University School

of Naples, for assiduous scientific support. Arthur P. Nestler,B.S.N., and Robin Coret, B.S., provided assistance with thepreparation of the manuscript.

Received, May 24, 2000.Accepted, November 2, 2000.Reprint requests: Hae-Dong Jho, M.D., Ph.D., Department of Neuro-logical Surgery, University of Pittsburgh Medical Center, Presbyte-rian, Suite B-400, 200 Lothrop Street, Pittsburgh, PA 15213. Email:[email protected]

REFERENCES

1. Asari KV, Kumar S, Radhakrishnan D: Technique of distortioncorrection in endoscopic images using a polynomial expansion.Med Biol Eng Comput 37:8–12, 1999.

2. Bouthillier A, van Loveren HR, Keller JT: Segments of the internalcarotid artery: A new classification. Neurosurgery 38:425–433, 1996.

3. Cappabianca P, Alfieri A, Colao A, Ferone D, Lombardi G, deDivitiis E: Endoscopic endonasal transsphenoidal approach: Anadditional reason in support of surgery in the management ofpituitary lesions. Skull Base Surg 9:109–117, 1999.

4. Cappabianca P, Alfieri A, de Divitiis E: Endoscopic endonasaltranssphenoidal approach to the sella: Towards functional endo-scopic pituitary surgery (FEPS). Minim Invasive Neurosurg 41:66–73, 1998.

5. Dietemann JL, Kehrli P, Maillot C, Diniz R, Reis M Jr, NeugroschlC, Vinclair L: Is there a dural wall between the cavernous sinusand the pituitary fossa? Anatomical and MRI findings. Neurora-diology 40:627–630, 1998.

6. Dolenc VV (ed): Anatomy and Surgery of the Cavernous Sinus.Vienna, Springer-Verlag, 1989.

7. Fujii K, Chambers SM, Rhoton AL Jr: Neurovascular relationships of thesphenoid sinus: A microsurgical study. J Neurosurg 50:31–39, 1979.

8. Harris FS, Rhoton AL Jr: Anatomy of the cavernous sinus: Amicrosurgical study. J Neurosurg 45:169–180, 1976.

9. Hashimoto N, Kikuchi H: Transsphenoidal approach to infrasellar tu-mors involving the cavernous sinus. J Neurosurg 73:513–517, 1990.

10. Inoue T, Rhoton AL Jr, Theele D, Barry ME: Surgical approachesto the cavernous sinus: A microsurgical study. Neurosurgery26:903–932, 1990.

11. Jho HD: Endoscopic surgery of pituitary adenomas, in Krisht AF,Tindall GT (eds): Pituitary Disorders: Comprehensive Management.Baltimore, Lippincott Williams & Wilkins, 1999, pp 389–403.

12. Jho HD: Endoscopy in skull base surgery. Skull Base Surg9[Suppl 2]:20–21, 1999 (abstr).

13. Jho HD, Carrau RL: Endoscopic endonasal transsphenoidal surgery:Experience with 50 patients. Neurosurg Focus 1:Article 2, 1996.

14. Jho HD, Carrau RL: Endoscopic endonasal transsphenoidal sur-gery: Experience with 50 patients. J Neurosurg 87:44–51, 1997.

15. Jho HD, Ha HG: Endoscopic endonasal skull base approach: Part2—The cavernous sinus. Minim Invasive Neurosurg (in press).

16. Jho HD, Carrau RL, Ko Y: Endoscopic pituitary surgery, inRengachary SS, Wilkins RH (eds): Neurosurgical Operative Atlas.Park Ridge, AANS, 1996, vol 5, pp 1–12.

17. Jho HD, Carrau RL, Ko Y, Daly M: Endoscopic pituitary surgery:An early experience. Surg Neurol 47:213–223, 1997.

18. Jho HD, Carrau RL, McLaughlin ML, Somaza SC: Endoscopictranssphenoidal resection of a large chordoma in the posteriorfossa. Neurosurg Focus 1:Article 3, 1996.

19. Kawase T, van Loveren H, Keller JT, Tew JM: Meningeal archi-tecture of the cavernous sinus: Clinical and surgical implications.Neurosurgery 39:527–536, 1996.



20. Krisht A, Barnett DW, Barrow DL, Bonner G: The blood supply ofthe intracavernous cranial nerves: An anatomic study. Neurosur-gery 34:275–279, 1994.

21. Laws ER Jr, Onofrio BM, Pearson BW, McDonald TJ, DirrenbergerRA: Successful management of bilateral carotid-cavernous fistu-lae with a trans-sphenoidal approach. Neurochirurgia (Stuttg)27:93–97, 1984.

22. Miyazaki Y, Yamamoto I, Shinouka S, Sato O: Microsurgicalanatomy of the cavernous sinus. Neurol Med Chir (Tokyo) 34:150–163, 1994.

23. Parkinson D: A surgical approach to the cavernous portion of thecarotid artery: Anatomical studies and case report. J Neurosurg23:474–483, 1965.

24. Parkinson D: Lateral sellar compartment: History and anatomy.J Craniofac Surg 6:55–68, 1995.

25. Renn WH, Rhoton AL Jr: Microsurgical anatomy of the sellarregion. J Neurosurg 43:288–298, 1975.

26. Rhoton AL Jr, Hardy DG, Chambers SM: Microsurgical anatomyand dissection of the sphenoid bone, cavernous sinus and sellarregion. Surg Neurol 12:63–104, 1979.

27. Sekhar LN, Møller AR: Operative management of tumors involv-ing the cavernous sinus. J Neurosurg 64:879–889, 1986.

28. Sekhar LN, Burgess J, Akin O: Anatomical study of the cavernoussinus emphasizing operative approaches and related vascular andneural reconstruction. Neurosurgery 21:806–889, 1987.

29. Seoane E, Rhoton AL Jr, de Oliveira E: Microsurgical anatomy of thedural collar (carotid collar) and rings around the clinoid segment ofthe internal carotid artery. Neurosurgery 42:869–886, 1998.

30. Taptas JN: The so-called cavernous sinus: A review of the con-troversy and its implications for neurosurgeons. Neurosurgery11:712–717, 1982.

COMMENTS

Until 30 years ago, the cavernous sinus was considered aforbidden area for surgery because of venous compartmentsand, hence, uncontrollable venous bleeding during a surgicalprocedure. The authors state in the Materials and Methodssection that the cavernous sinuses in five adult cadavericheads were studied after injecting the arteries with red latex.They also state that the veins were not injected because theaim was not to study cavernous sinus venous anatomy. Thereader may be surprised at the exclusion of venous compart-ments from the cavernous sinus studies.

The panoramic view of the walls of the sphenoidal sinus isdescribed from inside the sphenoidal sinus. The individual pro-tuberances, as well as grooves or depressions, are nicely de-scribed and systematically presented. The problem begins when,via the endoscopic approach, the structures in the parasellarspace are described using new nomenclature without taking intoconsideration the more or less generally accepted nomenclaturedescribed as seen from above by many authors during the last 3decades. When the authors describe the lateral wall of the cav-ernous sinus, the reader confronts even greater difficulty inunderstanding the description as seen from below. The authorsdo not give recognition to previous authors in describing thegasserian ganglion, because it is evident that this structure islocated outside of the so-called cavernous sinus in the parasellarspace. The same is true for Dorello’s canal. Those familiar withthe parasellar space, and in particular with the passage throughthe superior orbital fissure, will realize that the description of the

superior orbital fissure in this report is simplified to such anextent that it is far from the objective. It is difficult to understandwhy the authors believe that a new classification of the internalcarotid artery from their perspective is needed. They may realizethat it in fact brings greater confusion into the nomenclature ofthe parasellar structures and less understanding between theneurosurgical approach to the parasellar space from the trans-cranial epidural side through the lateral wall of the cavernoussinus and the approach used by the endoscopic group to theparasellar space through the sphenoidal sinus from below. It isas if the topography of the American continent, described andnamed by the settlers through the long period of moving fromthe East to the West coast, should now be renamed and/orredescribed by settlers who arrived from the Pacific.

This renaming is a waste of time and energy at the least.Even more importantly, on the basis of the 10 cavernoussinuses in five adult cadaveric heads studied, the knowledgeobtained by investigators who performed thousands of ca-daveric studies cannot be ruled out, starting with Taptas (3, 4)during the Second World War and continuing with manyother researchers, as well as the knowledge obtained fromstudying thousands of patients operated on for cavernoussinus pathologies. The presented anatomic study is welcomefor completing the description of the parasellar space as wellas for offering an additional possibility for performing biop-sies and some aspiration procedures in a limited number ofparasellar pathologies. The authors have made a very valu-able contribution to knowledge of the last facet of the entirespectrum of the anatomy of the parasellar space; however, itis imperative to realize that much of this territory was discov-ered long ago by Taptas (3, 4), Parkinson (1, 2), and otherpioneers.

Vinko V. DolencLjubljana, Slovenia

1. Parkinson D: A surgical approach to the cavernous portion of thecarotid artery: Anatomical studies and case report. J Neurosurg25:474–483, 1965.

2. Parkinson D: Carotid cavernous fistula, in Vinken PJ, Bruyn GW(eds): Handbook of Clinical Neurology. Amsterdam, North HollandPublishing Co., 1972, vol 12, pt 2, pp 267–288.

3. Taptas JN: La loge du sinus caverneux. Rev Otoneuroophthalmol21:193–199, 1949.

4. Taptas JN: La loge du sinus caverneux: Sa constitution et lesrapports des éléments vasculaires et nerveux qui la traversent.Sem Hop Paris 25:1719–1722, 1949.

An important description of the anatomy and approach to thecavernous sinus by the endoscopic endonasal procedure is pre-sented in this article. Surgical landmarks essential for a success-ful operation on the cavernous sinus via the endoscopic endo-nasal technique are well described. The endoscope shows athree-dimensional image of the anatomy that is quite differentfrom the two-dimensional image of microscopic anatomy. Thisdescription provides the anatomic basis required by a neurosur-geon to be able to perform endoscopic endonasal transsphenoi-dal surgery on cavernous sinus pathology.

836 Alfieri and Jho


We think that the authors should increase the number ofcadaver specimens in their study to enlarge the experience withthis approach in different cases (e.g., specimens should be re-ported in which the sphenoidal sinus is not well pneumatized orseptated). In one of the five cadaver specimens, the authorsfound a bilateral absence of the fibrocartilaginous covering of the“foramen lacerum medium.” Is this a common anatomic variation?

The description of a new anatomic division for the cavern-ous portion of the carotid artery is original, and the use ofbone landmarks in an endonasal endoscopic image is helpfulto the surgeon in identifying different segments of the internalcarotid artery before opening the bone of the sphenoidalsinus. Alfieri and Jho have contributed an original article.

Fernando Campos Gomes PintoEvandro de OliveiraSão Paulo, Brazil

Endoscopic surgery has been used increasingly to provide atranssphenoidal approach to the sellar region. An advantage ofthe endoscope may be to support microsurgery by giving theneurosurgeon a means by which to visualize the blind corner inthe sphenoidal sinus or inside the tumor lumen with the use ofan angled lens. Without distinct anatomic landmarks, however,the surgeon sometimes becomes disoriented in the sphenoidalsinus while observing through the endoscope.

This study, which describes the precise anatomy of thesphenoidal sinus, is educationally useful for surgeons who arebeginning to use the endoscope. Opening the cavernous sinusby cutting the periosteal wall may not be realistic under theendoscope because of difficulty with control of massive hem-orrhage from the sinus. In the case of a pituitary adenoma ora suprasellar chordoma showing lateral extension, however,the cavernous sinus is packed or pushed laterally by thetumor, and structural knowledge of the medial cavernoussinus through the endoscope is important.

Takeshi KawaseTokyo, Japan

The authors provide an excellent review of the anatomy ofthe sella and cavernous sinus as seen by the endoscopictranssphenoidal approach. Many of the illustrations are sim-ilar to those that have appeared in other articles and in mybook on the orbit and sellar region; in addition, this articledemonstrates distortion of the anatomy as seen through the

endoscope (1, 2). The authors have made an excellent case foran endoscopic approach to the cavernous sinus.

In an effort to reduce the facial trauma associated with subla-bial and transseptal transsphenoidal surgery, we have devel-oped an endonasal approach directed through one nasal passagebetween the septum and turbinates that does not require theremoval of any of the septum or a sublabial incision. The open-ing in the anterior face of the sphenoidal sinus with the endo-nasal approach is similar to that used with the endoscopic ap-proach but allows the structures to be visualized with theoperating microscope. This method has been used not only toapproach the intrasellar contents but also in selected cases forremoval of tumor that extends around the carotid artery into themedial part of the cavernous sinus. Exposure of these areas hassometimes been combined with image guidance. The addition ofimage guidance to the procedure allows one to display the site ofthe carotid artery accurately to direct the approach to the tumorlateral to the artery in the cavernous sinus. With the endonasalapproach, the speculum is placed in the right nostril if the leftcavernous sinus is to be visualized and in the left nostril if theright cavernous sinus is to be visualized. The view of the open-ing into the sella is similar when either the microscopic endona-sal approach or the endoscopic approach is used. Intranasalpacking is not necessary after use of the endonasal approach,which in most cases is completed in less than 90 minutes. Onedisadvantage of the endoscopic approach for tumors locatedwithin the sella is that the diaphragm often settles down againstthe floor of the sella as the removal proceeds. The protrudingdiaphragm blocks the lateral endoscopic view of the cavernoussinus when the majority of the tumor has been removed. Theauthors have conducted an excellent endoscopic study of cav-ernous sinus surgery.

Albert L. Rhoton, Jr.Gainesville, Florida

1. Fujii K, Chambers SM, Rhoton AL Jr: Neurovascular relationshipsof the sphenoid sinus: A microsurgical study. J Neurosurg 50:31-39, 1979.

2. Rhoton AL Jr, Natori Y: Orbit and Sellar Region: Microsurgical Anat-omy and Operative Approaches. New York, Thieme Medical Publish-ers, Inc., 1996.



endoscopic endonasal cavernous sinus surgery: an anatomic study

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