| Background The cavernous sinuses (CS) located in the middle cranial base, the lateral sella turcica and pituitary gland, has intricate anatomic relations with surrounding structure, also be surrounded by dural mater, the pituitary capsule, the periosteum of the sphenoid bone. CS drained venous blood from large range, such as the superior and inferior ophthalmic veins; the vein of the foramen rotundum, foramen ovale, and foramen spinosum; and the deep middle cerebral vein and superficial sylvian vein, also has great deal of effluent canals, such as superior and inferior petrosal sinus. In addition, it connected the intracranial and extracranial veins. Two sides of CS were joined by basilar sinus. Surgical treatment of CS lesion will take the grest risk, because of great difficulty of hemostasis and large quantity of haemorrhage. Dense nerves course through the lateral wall of CS, which have important function. Mobilization of the nerve is very difficult in surgery, the operation only can base on its nature interspace, which limited the range of intraoperative exposure and increased the difficulty of intraoperative exposure.The cavernous sinus is an envelope containing ICICA and its branches, the abducene nerve, the sympathetic plexus. Relations between ICICA and medial, lateral wall of CS have great variety that required the operator must to protect ICICA and its branches, the abducene nerve carefully. Because it's complex anatomic relations with surrounding strcture, dense important neurovascular structures within it and its deepest position, made lesions in this area were deemed unresectable in the past. In 1963, Parkinson as a pioneer described a direct surgical approach to the CS for a carotid cavernous fistula successfully. Neurosurgeon was very invigorated. More and more anatomists and neurosurgeons focus their study on the anatomic structures of CS. With the development of the neurosurgical equipment, the advance of the operative technology, the improvement of the approachs to CS, the accumulation of the operative experience constantly, also got a great significant achievement about the applied anatomy on CS, made more and more tumor happened in CS can be complete resected. Frankly, the operation on CS still is a big challenge for neurosurgery. Furthermore, clearly understand the anatomic structure of CS and its surrounding structure is most important thing for a successful operation. Objective To provide anatomic basis for the operation of CS, Also provide anatomic data for imaging diagnosis of CS lesions.Methods Location, surrounding structures, structures of lateral wall, superior wall, medial wall and posterior wall of CS were dissected, observed and measured on 30sides from 15 cadaveric heads. Especially, focused on the following contents: 1. Dural structure, anatomic triangles and nerves of the lateral wall of CS. 2. Location and surrounding structures of ACP. 3. Location, course of the intracavernous internal carotid artery (ICICA) and its relations with the pituitary gland. 4. Location, course and surrounding structure of the abductens nerve.Results1. The lateral wall of the CS could be clearly divided into three layers, when it was dissected via the intradural approach to CS along the anterior petroclinoid fold.2. Bases on the interspace of the nerves on the lateral wall of CS, could be divided into four triangles: paramedial triangle, Parkinson's triangle, anterolateral triangle and lateral triangle. In 36.7% (11samples) there was no space between oculomotor nerve and trochlear nerve, therefore the paramedial triangle could not be exposed. In 13.3% (4samples), there was no space between trochlear nerve and ophthalmic nerve, Parkinson's triangle could not be exposed too.3. The leptomeningeal pockets of the oculomotor nerve, the depth in the anterior was (4.69±1.31) mm, and in the posterior was (6.50±1.58) mm.4. According to the course of trochlear nerve on the lateral wall of CS, could be classified into four types, found the type of the trochlear nerve near the ophthalmic nerve in 30%(9 samples), the type of the trochlear nerve near the oculomotor nerve in 33.3%(10 samples), 'S' type in 10%(3 samples), straight type in 26.7%(8 samples).5. The superior wall of CS, quadrilateral in shape, it could be divided into three triangles: the carotid triangle, the oculomotor triangle and the anteromedial triangle.6. The dural structures of the superior wall of CS had the falciform ligament, the anterior and posterior petroclinoid fold, the interclinoid ligament, the carotidoclinoid ligament, the carotid cave, the carotid collar, the leptomeningeal pockets of the oculomotor nerve, the clinoid space, the distal and proximal dural ring, et al. Dural structure formed complicated dural complex on the apex of the anterior clinoid process.7. ICICA was divided three type: First was 'Z' shape presence in 42.9%, second was 'S' shape presence in 35.7% and third was slanting 'L' shape presence in 21.4%.8. In 43.3% (13 samples) the ICICA were directly contacted with the pituitary gland, in the remaining 56.7% (17 samples) were not.9. The inferior venous compartment of CS presence in 93.3% (28 samples), the medial venous compartment of CS presence in56.7% (17 samples), and the superior venous compartment of CS presence in 73.3% (22 samples).10. The lateral aspect of the pituitary gland was divided longitudinally into superior, middle, and inferior thirds, the internal carotid artery (ICA) coursed some part of all the thirds of pituitary gland in 36.7% (11 samples); coursed some part of both the inferior and middle thirds of pituitary gland in 23.3% (7 samples); and coursed only the inferior third of pituitary gland in 33.3% (10 samples). In 6.7% (2 samples), ICA coursed the carotid sulcus below the level of the pituitary gland.11. Length of ACP in medial margin of optic canal (OC) was (9.90±1.27) mm; in lateral margin of OC was (5.29±1.24) mm; width of ACP in medial margin of OC was (12.19±3.44) mm; in lateral margin of OC was (6.74±1.71), thickness of ACP in medial margin of OC was (5.36±1.27) mm, in lateral margin of OC was (4.75±1.07) mm. The ACP contains air cells in 4 specimens (13.3%).12. The shape of the optic strut in the sagittal dissection was trigonal or oval, length was (5.94±1.70) mm, and thickness was (2.29±0.80) mm.13. Posteromedially ACP was intimately related to the clinoid segment of internal carotid artery (ICA), separated only by ICA collar. Inferiorly the oculomotor nerve and the trochlear nerve were very close to the lateral underside of the ACP. Optic nerve and ophthalmic artery situated anteromedially.14. The abducens nerve can be divided into five segments: the cisternal segment was (15.01±2.56)mm, the petroclival segment was(6.38±1.78)mm, the posterior segment of ICA was (2.81±1.32)mm, the segment of stride over the ICA was (5.76±0.84)mm, the anteroinferior segment of ICA was (15.63±2.03)mm.15. The abducens nerve exhibited three different angulations in its course from the external brainstem to the superior orbital fissure, located at the dural entrance porus, the petrous apex and the lateral wall of the cavernous segment of ICA.16. The abducens nerve had intimately relation with the medial clival artery, the lateral clival artery, the tentorial marginal artery, the inferior hypophyseal artery and the anterolateral branch of the inferolateral trunk.17. The triangle of abducens nerve was formed by the petrosphenoidal ligament, the medial wall of Meckel's cave and the posterolateral wall of ICA, the abducens nerve passed through this triangle constantly.18. Sympathetic fibres jioned the abductens nerves with acute angle on the lateral wall of ICA.Conclusion1. The leptomeningeal pocket of the oculomotor nerve can be opened to aid in the exposure and mobilization of the nerve, it also as an important landmark for approaches to the basilar apex, basal cisterns, middle cranial base, suprasellar area, and to the roof and lateral wall of the cavernous sinus.2. The initial incision beginning at the oculomotor foramen and extending alongⅢnerves should not be＞9.42 mm or there is risk of injuringⅣnerve.3. The paramedial triangle and the Parkinson's triangle have great variation, but combine these triangles will provide stable exposure for operation.4. The clinoid segment of the ICA and the clinoid venous plexus was intracavernous, the clinoid ICA is covered with a layer of membranous tissue be named the carotid collar, this tissue is periosteum which separate clinoid space with CS. Clinoidectomy was performed extradurally. The anterior clinoids were pierced by venous canals arising from the anterior cavernous sinus and running through the clinoid space that is the reason of blooding of removal of the anterior clinoid process.5. The tip of ACP, as a fulcrum of the dural complex, together with the superior wall dural structure build a fibrous framework, which provide a morphologic foundation for the LSC occur.6. The distance between two side of ICA and the width of pituitary don't have statistic relativity. The anatomic relations between ICICA and pituitary, can be looked as basis for judging the pituitary adenoma whether invaded CS or not on imaging diagnosis.7. The abducens nerve exhibited three different angulations in its course from the external brainstem to the superior orbital fissure, also had complex anatomic relationship with blood vessel, nerves, ligament and bone, that is the reason of its vulnerability.8. The triangle of abducens nerve was formed by the petrosphenoidal ligament, the medial wall of Meckel's cave and the posterolateral wall of ICA, the abducens nerve passed through this triangle, constantly. Can base on this triangle to find and identify the abducens on the radiological diagnosis and operating. In the same time, the branch of the MHT always present in this triangle that should be avoided to injure in treating CS lesion on operation.
|
PDF Full Text Request