| Background and Purpose:The cavernous sinuses are venous structures in the middle fossa.It is very difficult to expose due to its deep location.Many diseases in this region are needed to treat by surgery;therefore,it is very important to choose a better surgical approach. The cavernous sinus is an envelope containing the cavernous carotid segment and its branches;the sympathetic plexus;theⅢrd,Ⅳth,andⅥth cranial nerves;the first trigeminal division;and multiple venous tributaries and spaces.This study attempts to define the important relationships of the microsurgical anatomy for the various surgical approaches to the cavernous sinus.Cavernous hemangioma of the cavernous sinus is an uncommon lesion accounting for 0.2-2%of all cavernous sinus tumors[1].Although the tumor is benign,but it is a neurosurgical challenge due to the high vascularity,location within the cavernous sinus,and relationship to the intracavernous internal carotid artery and cranial nerves.Histologically,cavernous hemangioma of the cavernous sinus is similar to intracerebral cavernous angioma,but is a distinct clinical entity and the management issues are vastly different from those located within the cerebral parenchyma.Cavernous hemangiomas limit to the dura of the cavernous sinus,and frequently reach giant size before diagnosis.Cavernous sinuses of 19 adult cadaveric specimens were examined using×3 to×20 surgical microscope.We had obtained the anatomic parameter of the cavernous sinuses,and also summarized 12 cases of cavernous sinus hemangiomas to treat by surgery.Methods:1.AnatomyCavernous sinuses were examined in 19 adult cadaveric specimens using×3 to×20 surgical microscopes.The heads were injected with colored silicone,and the structure of cavernous sinus was investigated.In the study,we simulated surgical procedure to investigate 19 adult cadaveric heads.After head fixation in the Mayfield clamp,the skin incision is placed along or in the hair line starting in the preauricular region 1 cm below the zygomatic arc.The anterior superficial temporal artery is carefully located and protected during the coronal incision.A temporal subfascial dissection is performed to preserve the frontal branches of the facial nerve.As the scalp flap is elevated,the temporal fat pad will appear.After dissecting the lateral orbit and zygomatic arch,the zygoma is divided at either end and is displaced inferiorly on its masseteric pedicle.The temporalis muscle is elevated off the calvarium in subperiosteal fashion beginning low on the temporal squama and ending by disinserting the muscle at the superior temporal line.The cranioorbital flap is elevated as a single piece.A burr hole is placed in the keyhole to gain simultaneous entrance into the cranium and orbit.A second burr hole is placed posteriorly on the temporal floor.A cut is made from the medial aspect of the lateral orbital wall to its lateral aspect and is continued to the keyhole.The keyhole is then connected to the posterior burr hole by cutting through the temporal fossa.A cut starting at this burr hole is then brought superiorly to the frontal bone and then anteriorly through the supraorbital rim.The inferior orbital fissure is exposed after the orbital periosteum is separated from the osseous orbit.A wire saw is transferred through it below the zygomatic arc,and a cut of the lateral orbit is finished.A notched osteotome is used to incise the orbital roof from the second burr hole toward the nasion.The bone flap is now elevated.After opening dura,the sylvian fissure is opened in a lateral-to-medial manner and the carotid and chiasmatic cisterns are opened.This allows gentle retraction of the frontal and temporal lobe.The parasellar region,edge of tentorium and the base of middle fossa are exposed.The lateral wall of cavernous sinus is dissected under the microscope.After having finished the simulating surgical procedure,the remaining of the cranium and the dura of this area is removed.The cerebrum,the cerebellum and the brainstem are removed.We investigate the structures of cavernous sinus under the surgical microscope,measure the distances among the nerves and the arteries.2.Summarizing the clinical data:There were 2 males and 10 females.The ages ranged 28-61 years old.The duration of symptoms at the time of presentation ranged from 3 months to 2 years.8 patients presented with symptoms of headache,4 patients presented with symptoms of facial numbness.Two patients had visual deficits on the side of the tumor.The visual deficits were progressive in all patients.Two patients had oculomotor paralysis;two patients had abducent nerve lesion.Two patients had eyeball protrution.All patients were investigated with computed tomography(CT)and magnetic resonance(MR) imaging.CT showed the lesions as hypodense to isodense,and the lesions were demarcated and bell-shaped with marked enhancement after contrast administration. T1-weighted MR imaging showed the lesions as hypointense with marked enhancement after contrast administration.T2-weighted MR imaging showed the lesions as highly hyperintense.The size of the tumor ranged from 9 to 57 mm in maximum dimension(mean 45 mm).The surgical treatment was performed in all 12 patients.We adopted various ways to expose the lesions under the dura,according to the size of the lesions.The lateral wall of cavernous sinus was incised and the lesion was removed.There were 8 cases with zygomatic-pteroinal approach,2 cases with pteroinal approach and 2 cases with frontal-orbital-zygomatic approach in the surgical process.The sylvian fissures were dissected in 6 cases.Results:1.Frontal-orbital-zygomatic approach and structure of cavernous sinusIn all 19 adult cadaveric heads,inferior orbital fissures are wide enough to being tranfered the wire saws from them.After having simulated the frontal-orbital-zygomatic ctaniotomy,the intra-orbital structure,bases of anterior and middle fossas and the infratemporal fossa were exposed widely.①General relationshipsThe roof of the cavernous sinus is trapezoid being formed by the medial half of the lesser wing and the posterior dural membranous layer..The anterior border of this trapezoid corresponds to the anterior rim of the origin of the C2 portion of the internal carotid artery(ICA)medially and the lateral end of the superior orbital fissure laterally.The posteromedial point is the posterior clinoid process;the posterolateral point is the dural entrance of the fourth cranial nerve.The anterior clinoid process is situated above the anterior part of the roof.The floor is formed by the medial portion of the greater wing of the sphenoid bone,including the lower margin of the foramen rotundum anteriorly and foramen ovale posterolaterally.The medial wall of the cavernous sinus is formed by the lateral wall of the pituitary gland and the most medial greater wing.The middle clinoid process is a small eminence of the lateral part of the sella turcica,which forms the superior margin of the carotid sulcus,and the ICA courses between the anterior and middle clinoid processes.The lateral wall of the sinus consists of two membranous folds compressing an outer dural layer and an inner layer of loose connective tissue,which envelopes the third,fourth,and fifth cranial nerves.The inner layer around the third cranial nerve is rather thick and relatively easily dissected.However,the inner layer around the fourth cranial nerve and the first division of the fifth cranial nerve is thin and often firmly attached to the outer layer,resulting in an uniformly thick wall.The third cranial nerve penetrates the roof slightly anteromedial to the penetration site of the fourth cranial nerve,which forms the posterosuperior angle of the lateral wall of the cavernous sinus.At the anterior lateral wall,the third and fourth cranial nerves and the first division of the fifth cranial nerve meet just before entering the superior orbital fissure,where the two layers unite to form a thick single wall.As the third, fourth,and fifth cranial nerves approach the superior orbital fissure,the fourth cranial nerve courses inferolaterally to the third cranial nerve,which is situated immediately below the anterior clinoid process.The sixth cranial nerve pierces the dura mater lateral to the dorsum sellae,runs through Dorello's canal,and enters the posterior wall of the cavernous sinus,and then courses between the first division of the fifth cranial nerve and ICA within the cavernous sinus.The anterior wall is a relatively shallow rectangle formed by the anteromedial portion of the greater wing,which includes the superior orbital fissure above and the foramen rotundum below.The third and fourth cranial nerves and the first division of the fifth cranial nerve pass through the superior orbital fissure and the second division of the fifth cranial nerve passes through the foramen rotundum.The posterior wall is bounded by the ligament petroclinoidea posterior above, which forms the tentorial edge situated between the posterior clinoid process and the superior border of the petrous temporal bone,and the petrous apex below.The superolateral border of the clivus is situated at a point two-thirds along the medial border of the posterior wall.The trigeminal ganglion occupies the trigeminal (Meckel's)cave in the dura mater,covering the trigeminal impression near the petrous apex.It is medial to the petrous ICA and the posterior part of the cavernous sinus,and inferior to the greater petrosal nerve,the petrous apex,and the foramen lacerum.The first and second divisions of the fifth cranial nerve then pass forward into the cavernous sinus close to the lateral part of the posterior wall.The sixth cranial nerve runs through Dorello's canal and pierces the dura mater lateral to the clivus in the cavernous sinus.Within the cavemous sinus,this sixth cranial nerve courses along the carotid artery,medial and parallel to the first division of the fifth cranial nerve.②Arterial RelationshipsThe cavernous sinus contains the intracavernous segment of the internal carotid artery and its branches.The intracavernous segment begins at the intracranial end of the carotid canal superior to the foramen lacerum and lateral to the posterior clinoid process,where the petrous segment of the internal carotid artery enters the cavernous sinus.The petrous segment of the internal carotid artery passes between the cartilaginous foramen lacerum below and the petrolingual ligament above to become intracavernous.The petrolingual ligament extends from the lingual process of the sphenoid bone to the petrous apex.The intracavernous segment passes upward and forward along the carotid sulcus posterior to the optic strut and medial to the anterior clinoid process and exits the cavernous sinus by piercing the dura extending medially from the upper surface of the anterior clinoid process.The intracavernous carotid artery has five parts:1)the posterior vertical segment,2)the posterior bend,3)the horizontal segment,4)the anterior bend,and 5)the anterior vertical segment The anterior vertical segment,also known as the clinoidal segment,is short and can be exposed only with removal of the anterior clinoid process.It is surrounded by the carotid collar and the clinoidal venous plexus inside the carotid collar and is limited above and below by the upper and lower dural rings.The intracavernous carotid artery has two main branches.The first,the meningohypophyseal trunk,arises from the posterior bend.The second,the inferolateral trunk,also called the artery of the inferior cavernous sinus,arises from the horizontal segment.The meningohypophyseal trunk typically originates from the posterior bend of the intracavernous carotid artery and has three branches:1)the dorsal meningeal artery,2) the inferior hypophyseal artery and 3)the tentorial artery.The dorsal meningeal artery passes posteriorly in the direction of Dorello's canal and supplies the dura of the upper clivus.③Venous RelationshipsThe cavernous sinus has five venous spaces(anterial,medial,anteroinferior, posterosuperior,and lateral),which are defined according to their position in relation to the intracavernous carotid.The anterial venous space is located before anterial bend of ICA.The medial venous space is located between the intracavernous carotid and the pituitary gland.The anteroinferior venous space is located anteroinferior to the posterior bend of the intracavernous carotid.The superior and inferior ophthalmic veins or their common trunk usually opens into the anteroinferior venous space.The posterosuperior venous space is located between the intracavernous carotid artery and the posterior part of the roof of the cavernous sinus and is the site where the cavernous sinus joins the basilar sinus.The lateral venous space,located between the intracavernous carotid and the ophthalmic nerve,is narrow.The abducens nerve courses medial to the ophthalmic nerve in this space.The main venous channels that communicate with the cavernous sinus are from the orbit,cerebral hemisphere, posterior fossa,and contralateral cavernous sinus.The communications between the two cavernous sinuses are through the anterior,inferior,and posterior intercavernous sinuses and the basilar sinus.The anterior intercavernous sinus courses anterosuperior, the posterior intercavernous sinus courses posterosuperior,and the inferior intercavernous sinus courses below the pituitary gland.These sinuses can occur together or separately.The basilar sinus is located behind the dorsum sellae and upper clivus and communicates at the lateral edge of the dorsum sellae with both cavernous sinuses.④Triangles of cavernous sinusAnteromedial(Dolenc)triangle:medial edge is optic nerve,12.25±1.40mm: lateral edge is oculomotor nerve,20.13±1.27mm;edge of bottom,11.32±1.41mm.Medial(Hakuba)triangle:medial edge is line between lateral ring of ICA and margin of the posterior clinoid process,7.85±1.79mm;the length of lateral edge, 8.03±2.10mm;the length of edge of bottom,5.12±1.31mm.Carotid triangle:medial edge is dura of sellae diaphragma(11.93±2.88mm); lateral edge is interclinoid ligament(10.98±3.54mm);edge of bottom (10.76±2.38mm).Oculomotor triangle:Clinoid ligament(11.08±3.74mm);Anteropetroclinoid ligament(19.57±2.53mm);Posteropetroclinoid ligament(13.49±3.25mm).Supratrochlear triangle:Trochlear nerve(14.9±2.9mm);Oculomotor nerve (24.9±4.7mm);Tentorial edge(11.7±3.2mm).Parkinson's triangle:Trochlear nerve(15.72±3.15mm);Ophthalmic nerve(19.23±4.62mm);Tentorial edge(8.05±2.21mm).Mullan triangle:Ophthalmic nerve(22.23±3.16mm);Maxillary nerve (15.45±2.38mm);Line between foramen rotundum and superior orbital fissure (11.68±3.12mm).Lateral triangle:superior maxillary nerve(13.26±2.37mm);inferior maxillary nerve(7.28±1.51mm);line between the foramen rotundum and the foramen ovale(12.18±1.53mm).Kawase triangle:Superior petrosal sinus(15.68±2.15mm);Greater petrosal nerve (11.71±1.67mm);Trigeminal nerve(13.31±1.65mm).Posterolateral triangle:Greater petrosal nerve(11.65±1.768mm);Line between foramen spinosum and eminentia arcuata(14.12±1.78mm);Mandibular nerve (6.51±1.88mm).Inferomedial triangle:Line between Dorello canal and poster clinoid process (18.42±1.18mm);Line between trochlear nerve and Dorello canal(13.78±2.65mm); Petrous apex(13.72±2.15mm).Inferolateral triangle:Line between trochlearnerve and Dorello canal (11.87±1.69mm);Line between petrosal vein and Dorello canal(13.56±2.12mm); Petrous apex(13.68±2.38mm).2.Therapeutic effect of cavernous sinus hemangiomasThe lesions were totally removed in 5 patients,sub-totally removed in 4 patients and partially removed in 3 patients.None of the patients was dead.In the immediate postoperative phase,2 patients showed optic acuity recovery,3 patients showed oculomotor paralysis,6 patients showed facial numbness.Extraocular movements completely recovered in two patients about 3 months following surgery.The function of the fifth nerve partially recovered.At follow up after six monthes to 2 years,the lesions were not recurrence in 5 patients that were totally removed.Other patients were administered with radio-therapy,and were controled validly.Conclusion:1.The cavernous sinus is the most challenging region in neurosurgery due to its deep location and complex structure.It is very important to understand the microsurgical anatomy of cavernous sinus.To known this knowledge is helpful for preserving ICA and cranial nerves and minimizing bleeding during the surgical procedures.We find that the flap of frontal-temperal-zygomatic craniotomy as a whole flap can minimize bone defect.2.Operation is the best choice for cavernous sinous hemangioma.It was helpful to control bleeding through intradura and incising lateral wall of cavernous sinus.
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