【关键词】 垂体腺瘤；手术入路；解剖学
Anatomical observation of operative approach of pituitary adenoma
WU Changchu, LIU Liang, ZENG Zhicheng(the Medical College of Jishou University, Jishou Hunan 416000, China)
Abstract: Objective To put forward anatomic parameters about the pituitary adenoma for microneurosurgery. Methods The surgical anatomy of the operating spaces and vessels/ nerves nearby in the sellar region was studied in 30 cadaver brains. Results The distance was (21.73±3.72)mm between endostoma of internal cervical arteries(ICA), (11.77±3.34)mm between endostoma of optic canals, (20.92±4.58)mm between cavernous sinuses, transverse diameter of basilar sella was (13.57±4.21)mm, longitudinal distance was (13.61±3.18)mm, the distance from anterior sphenoidal wall to nares was (92.91±17.81)mm, the distance from midpoint of superciliary arch superior border to the tuberculum sellae was (62.24±14.17)mm, the distance from midpoint of superciliary arch superior border(MSASB) to the homonymy endostoma of optic canal was (53.45±16.91)mm, the distance from MSASB to the opposite side endostoma of optic canal was (62.24±20.80)mm, the distance from MSASB to the homonymy entrance of ICA was (69.81±21.96)mm, the distance from MSASB to the opposite side entrance of ICA was (78.40±27.46)mm, the distance from MSASB to the homonymy lap of ICA was (56.43±15.31)mm, the distance from MSASB to the opposite side lap of ICA was (64.53±17.01)mm, the distance from pterion to the root of pituitary stalk was (59.24±17.17)mm, the distance from pterion to anterior clinoid process was (45.51±10.55)mm, the distance from pterion to cavernous sinus was (43.72±9.48)mm. Conclusion The present results may be a guide for the microsurgery of the sellar region to avoid injury of the important nerves and vessels.
Keywords: pituitary adenoma；operative approach；anatomy
原发于垂体的肿瘤即垂体腺瘤，约占颅内肿瘤的10%左右，但在尸检中发现率为20%～30%。近年来，随着现代病理学、现代放射学、医学影像学技术、临床内分泌检测手段以及显微外科技术、设备的迅速发展，对垂体腺瘤的诊断手段有了显著的提高，治疗效果也有了很大改善［12］。临床上垂体腺瘤的显微手术需要详细的解剖学资料，本文对成人尸体头颅鞍区手术间隙及邻近结构进行了解剖学观察、测量，为临床上垂体腺瘤的显微手术提供参考依据。
1 材料与方法
成年人尸头颅标本30例，其中男性19例，女性11例。所有标本均无畸形及外伤改变，鼻窦内无异物、新生物及明显的炎性改变。全部标本的解剖操作均首先将尸头按手术体位固定在手术头架上，模拟手术入路按经蝶入路、经额入路、经翼点入路三种手术入路方式逐层解剖，并对解剖结构进行精确测量。根据三种手术入路需要确定相应的测量数值，所有数据测量均用游标卡尺（精确到0.01 mm）。采用SPSS11.5统计分析软件对观察数据进行分析处理，数据用均数±标准差(±s)表示。
2 结果
2.1 经蝶窦入路相关骨性结构的测量
30例尸头标本分别测量颈内动脉内口间距、视神经管内口间距、海绵窦间距、鞍底横径、鞍底纵径、蝶窦前壁至鼻孔的深度，测量结果见表1。表1 经蝶窦入路相关骨性结构测量
2.2 经额入路相关骨性结构的测量
30例尸头标本测量眉弓上缘中点到鞍结节的距离、眉上缘中点到同侧视神经管内口距离、眉上缘中点到对侧视神经管内口距离、眉弓上缘中点到同侧颈内动脉入口的距离、眉弓上缘中点到对侧颈内动脉入口的距离、眉弓上缘中点到同侧颈内动脉膝部的距离、眉弓上缘中点到对侧颈内动脉膝部的距离，测量结果见表2。表2 经额入路相关骨性结构测量
2.3 经翼点入路相关骨性结构的测量
30例尸头标本测量翼点到垂体柄末端距离、翼点到前床突的距离、翼点到海绵窦的距离，测量结果见表3。表3 经翼点入路相关骨性结构测量
3 讨论
经蝶入路要求手术医师熟悉以蝶鞍为中心的解剖结构，包括蝶鞍下方的蝶窦；上方的视交叉、下丘脑；后方的斜坡上段骨质；侧方的海绵窦及其内容物；蝶鞍内的垂体、垂体柄及鞍隔等［23］。蝶窦是位于蝶骨内的空腔，通过蝶窦开口与鼻腔相连，这种解剖毗邻关系提供了经鼻蝶窦手术入路进入蝶鞍周围结构的解剖学基础。内窥镜的使用为手术提供了更为广阔的视野，但是确定精确的手术解剖标志是非常重要的。后鼻孔上缘中鼻甲及犁骨都被用做经蝶手术标志。但是一旦手术进入蝶窦后，蝶窦后壁斜坡骨质及其周围骨性隆起将是最好的手术解剖标志。如将蝶窦腔分为中间腔、旁中间腔及外侧腔五部分。中间腔的骨性解剖相对简单，其中心是鞍底骨性隆起，旁中间腔位于斜坡骨质的侧方，其内包括颈内动脉隆起及颈内动脉－视神经三角。本文测得颈内动脉内口间距、视神经管内口间距、海绵窦间距，有助于顺利进入手术区域，同时避免损伤这些重要的解剖结构。手术中尤其注意识别视神经管隆起和颈内动脉管隆起。通过扩大经鼻蝶手术入路向侧方可以显露海绵窦，在切开其内侧壁后进入，直视海绵窦内颈内动脉，在切开颈内动脉的前床突周围硬脑膜环后可将其游离、牵开，显露其在海绵窦内的分支及其外侧的动眼神经、滑车神经、外展神经及眼神经等，完全可切除侵入海绵窦内侧壁的肿瘤；打开蝶骨平台可到达视交叉池，显露视交叉、垂体柄及垂体，可切除起源于垂体柄等部位的小病变或者哑铃形垂体瘤的鞍上部分。
经额入路的蝶鞍区手术，最主要的限制是视神经和视交叉，特别是视交叉为前置型时手术入路就更狭小［35］。当视交叉前间隙较大或肿瘤突入视交叉前间隙，使间隙变大时，额入路切除该部肿瘤，效果较为理想。测得眉弓上缘中点到鞍结节的距离、眉上缘中点到同侧视神经管内口距离、眉上缘中点到对侧视神经管内口距离，对于视交叉前置型垂体大腺瘤，如肿瘤不突入交叉前间隙，而隐蔽于视交叉之后时，可根据此测量结果切除鞍结节，打开蝶窦腔，经额－蝶窦入路直达垂体前叶，以安全切除肿瘤，达到减少并发症的目的。经额胼胝体下入路垂体腺瘤手术主要是在颈内动脉之间操作。在尸头标本上测得，大脑前动脉发起处，两侧颈内动脉内口之间距约为（21.73±3.72）mm。理论上，此各间距可以看作是手术操作避免动脉损伤的安全区间，超出上述范围都有损伤颈内动脉的危险。当然，手术时还应考虑到颈内动脉走行变异的可能，以免损伤颈内动脉而引起致命的大出血。从标本测量结果看，眉弓上缘中点至前颅窝后界(视交叉前沟、视神经管颅口、蝶骨小翼后缘)的距离约53.45 mm，该距离在49.66～61.10 mm范围内，只要距眉弓上缘中点不超过49 mm，基本上可避免误入颅中窝。鞍结节位于垂体窝前缘，距眉弓上缘中点约62.24 mm，据此可定位垂体前界。巨大垂体腺瘤经翼点入路手术切除过程中，手术多进行在鞍区的4个解剖间隙［2］：双侧视神经之间的Ⅰ间隙；视神经与颈内动脉之间的Ⅱ间隙；颈内动脉与动眼神经之间的Ⅲ间隙；视交叉后部与运动终板之间的Ⅳ间隙；另外巨大垂体腺瘤一般呈浸润性生长，肿瘤包膜常与颈内动脉、海绵窦、下丘脑、第三脑室等有粘连。因此鞍区重要结构的保护甚为重要。
从标本解剖过程看，在经翼点手术过程中要注意额骨颧突和额结节的两个所谓关键孔的位置要尽量靠近颅底，在两个孔间锯开时也要注意使线锯靠近颅底边缘，以防由于颅骨钻孔不够低或锯开时不够低而妨碍随后对颅底深处结构的显露，进而影响对鞍区及其周围组织的显露；经翼点入路最适合切除广泛侵袭的垂体腺瘤，与其它入路比较，不易发生残留，易于全切。有特殊的体位使之能够利用脑的自然间隙进行操作，视野角度最大，操作中能充分解剖各脑池［3］。另外从术者的视线和肿瘤的显露上看：同侧视神经、视束下方和同侧颈内动脉床突上段内侧的区域被三者遮挡，是视线不能达到的盲区。但是同侧视神经下方及海绵窦侧壁旁的肿瘤往往都是侵袭性严重的肿瘤［45］。因此需要将间隙Ⅱ打开并轻度向外牵拉颈内动脉，才能得到较好的显露，否则可能导致周围重要结构的损伤。本文测得翼点到垂体柄末端距离约为59.24 mm，翼点到海绵窦的距离约为43.72 mm，翼点到前床突的距离约为45.51 mm，这些指标可以顺利到达鞍区，利于肿瘤切除减少结构损伤。
近年来，随着影像学、立体定向和显微外科技术的不断发展，内窥镜立体定向手术逐渐被外神经外科医生所重视，并成为微侵袭神经外科的发展方向之一。神经内窥镜不但能够提供良好的照明，而且能发现正常角度下难以发现的病变，在一定程度上消除了肿瘤切除手术中的死角，提高了垂体腺瘤的全切率［56］。手术者熟悉相关的组织结构的显微解剖学特点，并掌握手术入路相关的解剖学参数，才能选择合适的手术入路。
【参考文献】
［1］ 吴 浩，刘海生，凌 锋.经鼻-蝶窦入路的内镜鞍周解剖学研究［J］.神经疾病与精神卫生，2004，4（6）：420-422.
［2］ 刘丕楠，张亚卓，艾 林，等.内窥镜下经鼻腔-蝶窦入路切除垂体腺瘤的解剖学研究［J］.中华神经外科杂志，2000，16（1）：16-18.
［3］ 丰育功，朱贤立，马廉亭，等.经翼点入路鞍区手术间隙的显微解剖研究［J］.中华神经外科杂志，2000，16(4):222-225.
［4］ 朱广廷，刘晓震，刘 斌，等.影响巨大垂体腺瘤手术疗效的几个问题探讨［J］.中国神经外科杂志，2003，3(8):169-171.
［5］ 马玉新，殷林祥，毛培军，等.经单鼻孔蝶窦入路垂体腺瘤切除45例分析［J］.局解手术学杂志，2007,16(1):25-27.
［6］ 零达尚，杜建新.垂体腺瘤的手术入路［J］.临床和实验医学杂志，2007，6（6）：165-169.
作者单位：吉首大学医学院，湖南 吉首 416000
1 Department of Ophthalmology, Royal Victoria Infirmary, Newcastle upon Tyne, UK
2 Research Associate, Centre for Health Services Research, University of Newcastle upon Tyne, Newcastle upon Tyne, UK
3 Department of Ophthalmology, University of Newcastle upon Tyne, Newcastle upon Tyne, UK
4 Academic Unit of Ophthalmology and Orthoptics, University of Sheffield, Sheffield, UK
5 Department of Psychology, University of Sheffield, Sheffield, UK
ABSTRACT
Aims: To establish the range of normal distance stereoacuity in young children using the Frisby Davis distance stereotest (FD2).
Methods: Children passing preschool vision screening assessments underwent measurement of distance stereoacuity with the FD2 using a standard testing protocol.
Results: 59 visually normal children aged between 36 months and 68 months were recruited to this study. All 59 were able to understand the test requirements and were examined with the FD2 stereotest. Four (6.8%) had no measurable stereoacuity; 13 (24%) had stereoacuity measurable only at a 3 metre testing distance (mean 92.3 seconds of arc; SD 52.6). These children were significantly younger than the remaining 42 (76%) who demonstrated a stereoacuity response at a 6 metre testing distance (mean 29.6 seconds of arc; SD 13.1, p = 0.008).
Conclusion: The FD2 stereotest enables the measurement of distance stereoacuity in young children. There appears to be a maturational effect with distance stereoacuity improving between 36 months and 68 months. The data on age related normal values will provide a baseline from which to compare outcomes in clinical populations.
Abbreviations: FD2, Frisby Davis distance stereotest
Keywords: distance stereoacuity; Frisby Davis distance stereopsis test; children
Stereopsis is the perception of depth on the basis of binocular disparity.1 Tests of near stereoacuity—for example, TNO, Randot, Frisby, are used in the management of strabismus and amblyopia. The measurement of distance stereoacuity provides useful information regarding the management of strabismus primarily affecting distance fixation.2–5
Measurement of stereopsis to distant targets is possible using the synoptophore, the AO Vectographic Project-O-Chart Slide test, and the MentorII-SG B-VAT (Baylor Video Acuity Test-Mentor system 2). The latter two tests require the patient to wear spectacles. The AO Vectographic Project-O-Chart Slide test uses polarising lenses on a phoropter, generating disparities from 480–30 seconds of arc.6 The Mentor II-SG B-VAT uses liquid crystal goggles and generates disparities from 240–15 seconds of arc.7
Most of the studies using these methods of distance stereopsis measurement have been performed on patients who are 5 years and older although one study used children 4 years and older.2–5,8,9,10,11,12 As the majority of cases of paediatric strabismus present before the age of 5 years, these tests have had limited clinical application. No study to date has measured distance stereopsis in children as young as 3 years.
In an attempt to overcome this difficulty two of the authors (JPF and HD) invented the Frisby Davis distance stereotest (FD2) as a child friendly, free space test of real depth.13 We undertook to assess the ease with which this test could be delivered and to establish the range of values that could be achieved in young, visually normal children.
PATIENTS AND METHODS
Patients
Distance stereoacuity measurements were obtained from children undergoing preschool vision screening. The majority (57/59) of the children were white and as far as could be ascertained, developmentally normal.
All the children had their visual acuity tested at 6 metres, using the Sheridan Gardner test. The presence of binocular single vision was assessed by an orthoptist who tested the near and distance cover test, the Lang-II Stereotest, and 20 dioptre prism test.
Those who achieved normal visual acuity and binocular single vision were then assessed for distance stereoacuity, using the FD2, by an independent examiner.
Methods
The FD2 test comprises a box containing four back illuminated and differently shaped plastic objects mounted on rods.
These are either four animal or four geometric shapes set in a transparent frame pointing towards the observer (fig 1).
Figure 1 FD2 stereotest using animal shapes. The animal shapes were used in this study.
The shapes are translucent but sufficiently dark to obscure the rods, giving the appearance that the shapes are free floating. One shape is set by the examiner to be nearer to the observer at each presentation and the test requirement is to identify this target. The size of disparity presented is altered by the amount by which the rod is set to protrude and by the distance of the observer from the targets, generating disparities from 200–4 seconds of arc.14
A testing protocol was written to establish comprehension of the test and to standardise the testing procedure (fig 2).
Figure 2 Testing protocol.
Comprehension of the test was established by asking the child, at 1 metre distance from the box, to name the animal shapes. One shape was set to protrude and the child was asked to identify which animal "jumped out" of the box. The testing was then performed starting with the largest disparity at 6 metres. If the child could not respond accurately at 6 metres then the distance was reduced to 3 metres and the procedure repeated. Recorded stereoacuity values took account of the test distance.
There were three possible outcomes on the test, recorded as follows:
Non-responder: unable to comprehend the test when presented with the largest disparity at 1 metre.
Negative: comprehension established at 1 metre but incorrect responses for two presentations at the largest disparity at 6 metres and then also at 3 metres.
Responder: comprehension established and stereoacuity measured to threshold, either at 6 metres or 3 metres.
Mean stereoacuity values were calculated for the group as a whole and then subdivided for those performing at 6 metres and at 3 metres. The data were examined for a correlation between age and level of stereoacuity achieved using Pearson product moment correlation.
RESULTS
Fifty nine children were examined, 34 male and 25 female. Mean age (SD) at testing was 47.7 (7.6) months (range 36–68 months). No child was classified a non-responder.
Table 1 summarises the data for the whole study group: 4/59 (6.8%) could comprehend but could not complete the test at 6 metres or 3 metres and were therefore classified as FD2 negative (age range 39–64 months).
Table 1 Summary of FD2 data for all children examined
The mean (SD) stereoacuity of the 55 responders was 44.5 (38.3) seconds of arc. Of these 42 (76%) were able to perform the test at 6 metres and 13 (24%) at 3 metres. The mean stereoacuity (SD) of those tested at 6 metres was 29.6 (13.1) seconds of arc and for those tested at 3 metres was 92.3 (52.6).
Children who were only able to complete the test at 3 metres were significantly younger than those who performed the test at 6 metres (t = 2.746, df = 53, p = 0.008, two tailed). To maintain the integrity of the data, "6 metre failures" were excluded from further analysis.
A statistically significant relation between age and FD2 stereoacuity is still apparent in the group successfully performing the test at 6 metres, as shown in figure 3 (Pearson product moment correlation coefficient: –0.473, p<0.002, two tailed n = 42).
Figure 3 Relation between FD2 stereoacuity and age in those children who completed the test at 6 metres.
Table 2 shows the suggested age related normal values for those tested at 6 metres. Values have been rounded to the nearest measurable stereoacuity threshold. The values presented for the younger children are tentative as they are limited by the small sample.
Table 2 Suggested FD2 stereoacuity norms (seconds of arc) (SD) for children 48 months and <48 months performing the test at 6 metres.
DISCUSSION
The data presented in this study show that children as young as 39 months, with normal vision and ocular alignment, are easily able to perform the FD2 distance stereoacuity test.
As far as we are aware this is the first commercially available distance stereoacuity test that can be utilised in this age group.
Despite demonstrating comprehension of the test at 1 metre in all the children, there were a small number who could not respond at either of the set test distances (negative responders). It is possible that these children had defective distance stereoacuity but it is our impression that they failed because of an inability to cope with the cognitive challenges of testing—that is, attention, concentration, etc, rather than because they possess a less mature stereoscopic vision system. Stereoacuity arises between 3 months and 5 months of age but does not reach adult levels until around 3–7 years, depending on which test is used, and such challenges are therefore common when testing young children.15–19
Consistent with this we found that performance on the test was influenced by age—that is, younger children often showed poorer responses at 6 metres but responded well at 3 metres.
The FD2 is constructed as a real depth, free space test enabling assessment of stereoacuity without dissociating the eyes. This type of construction reflects binocular viewing as it occurs in everyday life but there is the potential to allow positive responses based on perception of monocular cues.
The test was developed to keep such cues to a minimum, as described in the FD2 test booklet; however, a recent study on monocular cues, using the FD2, in older patients has led its authors to propose a revised test protocol introducing a monocular test phase after binocular testing is complete.14,20
When using the standard FD2 testing protocol, young children do not seem susceptible to monocular cues, but it remains a possibility and could have resulted in an overestimation of performance. The application of the FD2 test in clinical practice is the subject of an ongoing study.
The suggested age related normal values in this study provide a useful reference from which to compare data in clinical populations. While this study sample is small, no other study to date has provided normal data in this age group. It is envisaged that the FD2 will prove a useful tool in the evaluation of binocular status, especially in intermittent exotropia.
Work has already been undertaken in patients with intermittent exotropia using the BVAT mentor, some of which suggests that measurements of decreasing distance stereoacuity may provide an indication for surgical intervention.3–5,11
Studies are under way using the FD2 in patients with intermittent exotropia and results are awaited from them.
CONCLUSION
The FD2 stereotest enables the measurement of distance stereoacuity in young children; however, there appears to be a developmental effect of age on distance stereoacuity. The reported data presented here on age related normal values, will provide a baseline from which to compare outcomes in clinical populations.
REFERENCES
Bishop PO. Binocular Vision. In: Moses RA, Hart WM, eds. Adler’s physiology of the eye: clinical application. St Louis: CV Mosby, 1987:619–89.
Zanoni D, Rosenbaum AL. A new method for evaluating distance stereoacuity. J Pediatr Ophthalmol Strabismus 1991;28:255–60.
O’Neal TD, Rosenbaum AL, Stathacopoulos RA. Distance stereoacuity improvement in intermittent exotropic patients following strabismus surgery. J Paediatr Ophthalmol Strabismus 1995;32:353–7.
Stathacopoulos RA, Rosenbaum AL, Zanoni D, et al. Distance stereoacuity. assessing control in intermittent exotropia. Ophthalmology 1993;100:495–500.
Yildirim C, Altinsoy HI, Yakut E. Distance stereoacuity norms for the mentor BVAT II-SG video acuity tester in young children and young adults. J AAPOS 1998;2:26–32.
Pratt-Johnson JA, Tillson G. Management of strabismus and amblyopia: a practical guide. New York: Thieme Medical, 1994:39.
Instruction manuals:. B-VAT II-SG Video Acuity Tester. Norwell, MA: Mentor O&O, 1987.
Mehta AM, France TD. Distance stereoacuity in children and teenagers with normal near stereoacuity. Am Orthopt J 1997;47:144–7.
Yildirim C, Mutlu FM, Chen Y, et al. Assessment of central and peripheral fusion and near and distance stereoacuity in intermittent exotropic patients before and after strabismus surgery. Am J Ophthalmol 1999;128:222–30.
Rutstein RP, Corliss DA. Distance stereopsis as a screening device. Optom Vis Sci 2000;77:135–9.
Rutstein RP, Corliss DA. BVAT Distance vs near stereopsis screening of strabismus, strabismic amblyopia and refractive amblyopia; a prospective study of 68 patients. Binocul Vis Strabismus Q 2000;15:229–336.
Parks MM. The monofixation syndrome. Trans Am Ophthalmol Soc 1969;67:609–57.
Davis H, Frisby JP, Walters BC. The Frisby Davis distance stereotest (FD2). In: de Faber J-T, ed. Transactions of 27th Meeting European Strabismological Association. Lisse: Swets and Zeitlinger, 2001:33–6.
Frisby Davis Distance. (FD2) Stereotest Booklet. Test design and test instructions.
Birch EE. Stereopsis in infants and its developmental relation to visual acuity. In: Simons K, ed. Early visual development: normal and abnormal. New York: Oxford University Press, 1993:224–36.
Fox R, Patterson R, Francis EL. Stereoacuity in young children. Invest Ophthalmol Vis Sci 1986;27:598–600.
Heron G, Dholakia S, Collins DE, et al. Stereoscopic threshold in children and adults. Am J Optom Physiol Opt 1985;62:505–15.
Simons K. Stereoscopic norms in young children. Arch Ophthalmol 1981;99:439–45.
Walraven J, Janzen P. TNO stereopsis test as an aid to the prevention of amblyopia. Ophthalmic Physiol Opt 1993;13:350–6.
Holmes JM, Fawcett S. Testing distance stereoacuity with the Frisby-Davis 2 (FD2) test. Am J Ophthalmol 2005;139:193–5.
