| Background:Temporal bone lies at the junction of middle posterior cranial fossa and middle superior of the area between os petrosum and clivus, the place around which is the predilection site of neoplasms. And neoplasms often encroach and surround petrous apex, cavernous sinus, foramen lacerum, clivus, foramen auditoria interna, foramen of tentorium of cerebellum and the third to eighth cranial nerves. Because of the deep location of neoplasms, the complex anatomy of os petrosum, and there are many important neurovascular structures in or around it, neoplasms here have been one neurosurgical operational difficulty. By the 1960s, with the development of operative approach of cranial base, especially the application of microsurgical technique, the total resection rate of neoplasms around os petrosum has been greatly improved, and operative mortality has declined markedly. The operative approaches of neoplasms around temporal bone include os petrosum anterior approach, posterior approach and combined approach. Os petrosumanterior approach is often used when the main body of neoplasms locate before os petrosum, while posterior approach is used when it is behind os petrosum. No matter which approach we choose), when we deal with neoplasms which have invaded petrous apex, the exposed extent of operation mainly depends on the stripping circumsciption of petrous apex, and accurately positioning cochlea is the key to strip petrous apex. So far, the lack of a fast, concise and pragmatic cochlea localization method makes it common that internal labyrinthus oticus is damaged during petrous apex stripping operation. We dissected 13 cases of adult skull specimens and observed the position relation between auris interna of pars petrosa ossis temporalis and the important surrounding structures. This provides anatomical information for the establishment of a fast and accurate cochlear positioning, and the safe stripping circumscription of apex partis petrosae ossis temporalis in clinical os petrosum anterior and posterior approach. At the same time, we took another two cases of skull specimens to simulate os petrosum anterior and posterior approach, got the whole anatomical observation, located cochlea during operation, and stripped sclerotin of tip of petrous bone.Objective:1. Through anatomical measurement and analysis about the spatial position relation between cochlea and the important anatomical structures surrounding it, to raise respectively one method which is suitable for positioning cochlear exactly and conveniently by os petrosum anterior or posterior approach, and to provide anatomical information and methods for positioning and protecting cochlea during operation.2.Under the guidance of original cochlea localization method, to raise one method, accurate and convenient , which limits the safe stripping circumscription of petrous apex during os petrosum anterior and posterior approach, so as to guide a safe and quick removal of sclerotin of petrous apex by os petrosum anterior and posterior approach, and then expose object construction of operation.Methods:Sampling randomly of 13 cases (26 sides) of 10% formalin-fixed wet adult skull specimens, sawing asunder calvaria along superciliary arch to the upper edge of eminence of occipital bone with conventional craniotomy instruments, and cutting off two sides of fasciculus opticus at the posterior chiasm opticum plane, removing cerebrum, cerebellum and diencephalon while brainstem reserved only, then middle cranial fossa base and posterior cranial fossa base were showed clearly. Corresponding anatomic structures were exposed with dental drill, spatial position relation of each target structures between the anatomical location can be observed, and then metered data was collected with sliding caliper. Using statistical packages of Spss 10.0 in order to get the descriptive statistics of relevant statistical data and matching T-test.Results:1. Trigeminal nerves, abducent nerves, facial nerve and the branches of them go around os petrosum, protection should be taken as possible while operation. When stripping the sclerotin of apex partis petrosae ossis temporalis, which lies out lateral inferior ganglion nervi trigemini, trigeminal nerves can move downward, outward, because of the feature of itself. This profits for exposing the area between os petrosum and clivus, and posterior part of cavernous sinus. Abducent nerve goes out of pontobulbar sulcus, upward along clivus at cisterna pontis, and crosses cavernous sinus through Dorello tube, which lies at oblique fissure of os petrosum of the medial of apex partis petrosae ossis temporalis. Thus, when stripping sclerotin of petrous apex during os petrosum posterior approach, the site where abducent nerve entering Dorello tube should be protected consciously. The superficial sclerotin of ganglion geniculatum nervi facialis may get damaged, therefore, there may be part of nervus petrosus superficialis major exposed in fossa cranii media base, in a word, it asks specially careful when applying fossa cranii media approach. In addition, damage of the mastoid segment of facial nerve should be avoided when stripping sclerotin of mastoid portion during translabyrinthine approach and presigmoid approach.2. Set point A for ganglion geniculatum nervi facialis, point B for the medial margin of internal acoustic pore, then make a straight line from point B, which is vertical to nervus petrosus superficialis major, while foot of a perpendicular is point C. Under such conditions of anthropogenic setting, Cochlea just lies in the decocted later of triangle ABC formed by the connections of A, B, C, Which locates cochlea accurately. During the os petrosum anterior operative approach, it will not damage cochlea when stripping sclerotin of petrous apex on the medial of line BC.3. Set point D for petrous apex, the safe stripping circumsciption of petrous apex during the os petrosum anterior operative approach is: petrous apex for the medial, line BC for the lateral, it means that triangle BCD is the safe stripping circumsciption of petrous apex. We can get an operative space of (0.968±0.183)cm2 after stripping the area of triangle BCD.4. Set point F for foramen spinosum, point E for the abouchement between inferior petrosal sinus and jugular foramen it won't damage bony labyrinth when stripping the sclerotin of petrous apex on the inside of line BF and line BE. The safe stripping circumsciption of petrous apex in the os petrosum posterior operative approach is: the outside is formed by the line from the medial margin of internal acoustic pore to foramen spinosum (line BF), and the line from the medial margin of internal acoustic pore to the abouchement of inferior petrosal sinus and jugular foramen (line BE). The mental state includes oblique fissure of os petrosum and inferior petrosal sinus. The most prozone is posterior vessel wall of arteria carotis interna, behind os petrosum, and posterior inferior wall of demilune node of trigeminal nerves. The posterior limit reaches to the level of foramen auditoria interna. In other words, sclerotin in the area of triangle BDE and BDF can be stripped safely. The stripping areas respectively are as following: S△BDE equals to (1.001±0.072)cm2, S△BDF is (1.224±0.064) cm2 and S△BEF is (1.148±0.056) cm2 .5. When stripping the superficial sclerotin of intracranial aneurysm(ICA) behind os petrosum, the stripping thickness of sclerotin should not exceed (0.235±0.067) cm from anterior to posterior, should not exceed (0.826±0.041)cm from posterioe to anterior, and the stripping thickness of sclerotin should not exceed (1.213±0.148)cm down by the cristae of os petrosum. Do not hurt cochlea when liberating intracranial aneurysm (ICA).Conclusion:1. Cochlea is in the decocted later of triangle ABC formed by the connections of A, B,C, Which locates cochlea accurately. During the os petrosum anterior operative approach, it will not be harmful to cochlea when stripping sclerotin of petrous apex in the medial of line BC.2. The safe stripping circumsciption of petrous apex in the os petrosum anterior operative approach is: petrous apex for the medial, line BC for the lateral, it means that triangle BCD is the safe stripping circumsciption of petrous apex. we can get an operative space of (0.968±0.183)cm2 after stripping the area of triangle BCD.3. It will not damage bony labyrinth when stripping the sclerotin of petrous apex on the inside of line BF and line BE. The safe stripping circumsciption of petrous apex in the os petrosum posterior operative approach is: the outside is formed by the line from the medial margin of internal acoustic pore to foramen spinosum(line BF), and the line from the medial margin of internal acoustic pore to the abouchement of inferior petrosal sinus and jugular foramen(line BE). The mental state includes oblique fissure of os petrosum and inferior petrosal sinus. The most prozone is posterior vessel wall of arteria carotis interna, behind os petrosum, and posterior inferior wall of demilune node of trigeminal nerves. The posterior limit reaches to the level of foramen auditoria interna. Area of triangle of BCD, which is the safe stripping region of petrous apex, can be stripped, and then an operative space of (0.968±0.183)cm2 can be gotten.4. When exposing intracranial aneurysm(ICA) behind os petrosum, the stripping thickness of sclerotin should not exceed (0.235±0.067) cm from anterior to posterior, should not exceed (0.826±0.041)cm from posterioe to anterior, and the stripping thickness of sclerotin should not exceed (1.213±0.148)cm down by the cristae of os petrosum. |
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