The Study On The Microdissection And Related Operative Approaches Of The Anterior Space Of Tentorial Notch Incisura

Part 1 The Study on the Microdissection of the Anterior Space of Tentorial Notch IncisuraObjective: To supply related anatomic data for clinical operation by studying the micranatomic features of the cisterns, nerves, blood vessels, bony and dura structures in the anterior space of tentorial notch incisura.Material and methods: 10 pre-fixed adult cadavers including 3 cases after perfusing the arteries with colored latex were applied in our study. Stepwise dissection was performed from the frontal pole with the aid of surgical microscope to observe the micranatomic features of the cisterns, nerves, blood vessels, bony and dura structures in the anterior space of tentorial notch incisura.Results:1. The distances between PCP,OMN door and the superior peduncle of ACP were (19.3±1.8)mm, (11.7±1.9)mm respectively. OMN triangle could be divided into the anterior and posterior OMN triangle by the line between the anterior edge of OMN door and homonymy PCP. Compared with anterior OMN triangle, the posterior OMN triangle was depressed and inclined towards lateral-interior-posterior direction, where the deepest position was the posterior edge of OMN door. The average distance between the posterior edge of OMN door and the line of both sides of PCP was 3.3mm.2. The arachnoid membrane of anterior cranial fossa could be divided into the upper and inferior layers in the line of limbus sphenoidalis and falciform fold. The upper arachnoid membrane belonged to trabeculum membrane, which constituted the upper arachnoid membrane of OC cistern and the posterior arachnoid membrane of olfactory cistern. The inferior arachnoid membrane belonged to basilar arachnoid membrane and stretched afterwards to constitute the arachnoid membrane of sellae diaphragma. The arachnoid trabeculas in OC cistern were intensive which enclosed stalk hypophysial and could be divided into three groups: upper-ahead group, posterior group and inferior group. The median sagittal plane and coronal plane of lamina terminalis cistern were rhombus and triangle respectively. The septal area and gyrus rectus constituted the lateral boundary of lamina terminalis cistern. PCoA membrane constituted the anterior boundary of PCoA cistern. LM was comprised by mesencephalic membrane, diencephalic membrane and hypothalamic membrane. Crural cistern was located between the lateral surface of cerebral peduncle and uncinate gyrus of temporal lobe, and its shape was quadrilateral. The posterior boundary of crural cistern had no obvious dividing mark with ambient cistern. AChA membrane constituted the anterior and medial boundary of crural cistern. Ambient cistern surrounded the lateral surface of upper brainstem which shape was"( )". Lateral pontomesencephalic membrane constituted the inferior boundary of ambient cistern. OMN cistern surrounded the posterior part of OMN mainly, and the anterior part of OMN lied in interpeduncular cistern mainly.3. The relationship between trochlear nerve and the free edge of the tentorium was intimate. Trochlear nerve was usually hided under the free edge of the tentorium and its length was (10.7±1.7)mm. The distance from the intersectional ponit between trochlear nerve and the free edge of the tentorium to PCP, petrous ridge were (25.1±2.6), (5.4±1.2)mm respectively. The frequency of OA in supraclinoid portion of internal carotid artery was 90%. All the starting points of OA were lied in interior-inferior direction of ACP and fully or partly covered by ACP. About 50% of the start points of SHA was located beyond ACP. In our study , we named the cone space between the 1/2 upper part of stalk hypophysial and the bottom of OC as the upper-anterior space of stalk hypophysial. The two sides of SHA shaped"collar"coincision and its second branches lied in the bottom of the space. There was crowded arachnoid trabecula in upper-anterior space of stalk hypophysial. PCoA could be divided into three sections of ICA cistern, PCoA cistern and interpeduncular cistern by means of the four points of the start point of ICA, PCoA membrane, the lateral edge of diencephalic membrane and PCoA point. Nearly all the branches of PCoA were located in the sections of PCoA cistern and interpeduncular cistern, which supplied the important area of the bottom of betweenbrain and cerebral peduncle. There were few branches in the section of ICA cistern which only supplied OC, OT. The average angle of the lap of MCA was (100.0±11.8)°. The branches of anterior 1/3 part of A1 were few and only supplied OC, OT. The perforating branches of A1 usually started from the middle 1/3 part of A1. 50% of ACoA lied in between the anterior border of OC and limbus sphenoidalis. 2 cases of BA furcation were below the level of the superior margin of dorsum sella. In ambient cistern, PCA was located in the interior-upper direction of the free edge of tentorium of cerebellum,and the both distance was (5.9±1.7)mm. SCA was located in the interior- inferior direction of the free edge of tentorium of cerebellum, and the both distance was (4.5±1.5)mm.Conclusions:1. The position of the superior peduncle of ACP was fixed and could be easily observed and looked as an important landmark. The posterior edge of OMN door could be looked as an important landmark of saddle area and superior petroclival region. Posterior OMN triangle belonged not only to the anterior space of the tentorial notch incisura but also to the superior petroclival region.2. All the cisterns in the anterior space of tentorial notch incisura belonged to the cisterns of base of skull, the really interfacing between the aboved cisterns was trabeculum membrane. The upper arachnoid membrane of anterior cranial fossa was trabeculum membrane and separated the cisterns of saddle area, parasellar area and suprasellar region. Diencephalic membrane was the anatomic landmark between the anterior and posterior saddle area. The upper arachnoid membrane of anterior cranial fossa and diencephalic membrane were the foundations of the complicated spatial constitution of the cisterns in the anterior space of tentorial notch incisura. PCoA cistern could be looked as a cistern among the OC cistern, ICA cistern, OMN cistern, crural cistern and interpeduncular cistern. Crural cistern was a passage contacted ambient cistern and interpeduncular cistern. The anatomic significance of dividing OMN cistern lied in it could contribute to comprehend the spatial constitution of part cisterns. 3. The upper-anterior space of stalk hypophysial could supply anatomic provision to protect SHA and its second branches. Arachnoid trabecula surrounded stalk hypophysial could provide a membrane landmark to protect stalk hypophysial when operating the pathological changes in upper-anterior space of stalk hypophysial.4. The operation of OA aneurysm should be adopted interventional therapy mainly. Occlusion technique was one of the mainly indications of the aneurysm origined from SHA. Limbus sphenoidalis was the safe posterior boundary when raising the frontal lobe. Part 2 The Study on the Related Operative Approaches of the Anterior Space of Tentorial Notch IncisuraObjective: To supply the reference of standardizing the selection of sugical approaches by comparing the frequently used surgical approachs in the anterior space of tentorial notch incisura.Material and methods: 6 pre-fixed adult cadavers were divided into 3 groups at random to simulate the approachs of pterion approach, subtemporal approach, subtemporal anterior transpetrosal approach. The micranatomic scope, contents, orders of the aboved approaches were observered with the aid of surgical microscope.Results:1. In pterion approach, the lateral border of space III was the plane constituted by the lateral border of diencephalic membrane, the membrane of OMN door and AChA membrane. The center of space III was OMN door. Space II could supply lager space and more observing structures and its center was PCoA. AChA and AChA membrane lied in the center of space V. The posterior boundry of pterion approach was located at 1cm below the upper margin of dorsum sellae.2. The anerior boundary of simple subtemporal approach was the campylodromous plane comstituted by the posterior wall of ICA, OMN door and AChA membrane. The observational field of the upper, inferior and medial boundary of simple subtemporal approach were restricted by the height of petrous ridge, anterior petroclinoid fold, the undersurface of temporal lobe and the reentry edge of temporal muscle. The enlarged subtemporal approach mainly expanded the observational field of lateral region of bridge of varolius contrasted with the simple subtemporal approach.3. Petrous segment of interal catoid artery(PSICA)lied in Glasscock's triangle which was paralleled with GSPN. The thickness of Glasscock's triangle was (5.9±1.6)mm. The biggest stripping scope of Kawase rhombus was (2.6±0.3)cm2. No important bony structures in"posterior internal auditory canal triangle". Cochlea lied in the inner part of"anterior internal auditory canal"and its surrounding sclerotin was hard. The posterior part of cavernous sinus, Meckel's cave, dorsum sella and superior petroclival region could be revealed after Kawase rhombus was stripped and its inferior level was inner acoustic meatus. The angles of coronal plane of subtemporal approach and subtemporal anterior transpetrosal approach were (14.8±3.0)°, (31.5±4.5)°respectively, the differences were significinant (P<0.05). the bony area was (0.9±0.2)cm2 after the inner petrous apex triangle was stripped, which enlarged the exposure of superior petroclival region, gaster-brain space and the bottom of betweenbrain.Conclusions:1. The anterior space of the tentorial notch incisura could be divided into anterior and posterior region of dorsum sella. The poterior region of dorsum sella belonged to superior petroclival region and gaster-brain space. Pterion approach was suited to explore the anterior region of saddle area. SpaceII was the main operation passage in pterion approach. Space I, III, V, V was the aid passage of space II.2. The exposure of subtemporal approach was superior to which of pterion approach, Posterior OMN triangle could not be exposed clearly and become the anatomic and operational"dead corner"in subtemporal approach.3. The subtemporal anterior transpetrosal approach could eliminate the"eave"effect of petrous ridge, lessen the stress of the temporal lobe, increase the exposure space of the posterior saddle area and partly anterior saddle area and eliminate the restriction of the"dead corner"formed by posterior OMN triangle. To master the anatomic courser of the important structures in os petrosum was the criticality of avoiding postoperative complications in subtemporal anterior transpetrosal approach. Larger operational space could be obtained after grinding medial triangle of petrous apex than simply grinding the Kawase rhombus, but the operation was more complicated.4. We had better choose the different plannings about the approach of the anterior space of tentorial notch incisura according to different individuals. It was a nice stragety that pterion approach should be adopted when the main tumour bodies lied in anterior region of dorsum sellae, otherwise subtemporal approach or subtemporal anterior transpetrosal approach should be adopted when the main tumour bodies lied in postzone of dorsum sellae.