Microanatomical Study Of Subtemporal Keyhole Approach

Middle cranial fossa and petroclival region which are the most densely neurovascular traveling region were in the base of the skull with the deep site and the anatomy complicated, and common pathological changes in the region also. The ordinary operation approaches often cause serious extracranial tissue injury, And the large-scale exposure of the operative vision need excessive traction, which sometimes lead to serious complications. The subtemporal approach provides short distance,vertical angle large for operation and well-exposure. After the petrous apex bone grinding the exposure may provide well-exposure for the petroclival region. But the conventional subtemporal approach brought large incision, large bone window, and serious temporal muscle injury, and bleeding, it also resulted in unnecessary exposure to brain tissue and bone structure of the destruction of the right temporal lobe surgery pull weight, which could easily lead to temporal lobe venous injury such as labble,, And it's hard to expose for right sphenoid ridge, middle cranial fossa, the medial, tumor revealed because of the temporalis muscle block of sight. With the development of micro-technology and minimally invasive keyhole concept, This study applied a new minimally invasive keyhole concept in the infratemporal approach, which based on the design of infratemporal keyhole. And it involved the simulation of microscopic anatomy and the experimental study on the feasibility which could provide the basis for clinical application.Objective Our research involves the microscopic anatomical characteristics of cavernous sinus lateral wall, side-saddle area, tentorial notch region and their relationships in the subtemporal keyhole approach. We hope the research provide some dissection tips and their applying during the real surgical operation.Materials and methods six adult healthy corpse (12sides) in 10% Formalin fixation and vascular perfusion were involved in the research, and subtemporal keyhole approach was simulated, the lateral wall of cavernous sinus, saddle-side area of tentorial region structure and microscopic anatomy between the nerves and blood vessels the distance were individually observed and measured under a microscope.Mayfield 3 nail head rack was used to fix the head. head position rotated 60 degrees to the opposite side, so that the level of the zygomatic arch remain horizontal position, reclined 15 degrees to the contralateral lateral flexion of 15 degrees to compensate for the middle cranial fossa-up tilt. A vertical lineal skin incision of approximately 5cm was created from the point at the superior rim of the zygomatic arch about 1cm anterior to the tragus. cut the temporal fascial in inverted Y-line,separate the muscles in the direction of flap incision. An oval-shaped craniotomy approximately 3cm in diameter is performed close to the cranial base. Grind the bone inside of the upper edge of the zygomatic arch. separate the child with the epidural meninges along the strip, we see the middle meningeal artery firstly and cut off it, in the rear bout 5.0 millimeters of it, the iwaasa nerve with petrous bone can be seen, the former can be seen within a 2.5 mm oval side hole and mandibular nerve. Cut the epidural layer surface of the mandibular nerve at the oval hole into the dural, sparate the dural out of the Lateral wall of the cavernous sinus, revealing Melkel cavity and the three branches of the trigeminal nerve, exposed the cavernous sinus lateral wall. separated the dura backwards to petrous bone, identify the trigeminal nerve (V3), rock shallow nerve, arcuate eminence, the internal auditory canal and other anatomical landmark hole, mill the DAY rhomboid, and then cut off the iwaasa nerve and use the spin-off sub-gently lift the trigeminal ganglia, mill the petrous apex of temporal bone to increase the petroclival area and the cavernous sinus exposure. Finally, incise the tentorial edge to expose the area of tentorial brain stem, cavernous sinus lateral wall and the side saddle area. Observe the anatomy and measure the distances between the nerves and blood vessels in lateral wall of cavernous sinus, saddle-side area, tentorial region with microscopic and then collecte videos. At last, the distance from the zygomatic arch to the intracranial cerebral, tentorial edge, anterior clinoid are measured after removing the skull cap,as well as the length and angle of the diagonal diamond district of the Day rhomboid. Data in this study was analysised by SPSS13.0 software,the result was indicated by mean±standard deviation (x±s),and the means were analysised by paired samples t test.Results①The shortest distances from the zygomatic arch to the tentorial edge,brain stem and anterior clinoid process are 41.1±5.1 mm,45.6±3.3 mm and 61.1±7.4 mm.②The fissureⅢcan be easily seen from the side-saddle area, the internal carotid artery streches from under the anterior clinoid process, whose horizontal segment produces posterior communicating artery, the later goes through the Liliquist membrane, along the branch sprouts 4 to 7 perforator arteries, after the internal carotid artery sprouts posterior communicating artery and after about 6 mm sprouts anterior choroidal artery. The oculomotor nerve penetrates from between the superior cerebellar artery and the posterior cerebellar artery, coming into the lateral wall of cavernous sinus from the tentorial edge. We can directly see the pituitary stalk from the interval of the oculomotor nerve and the posterior communicating artery, the posterior communicating artery and the anterior choroidal artery. Besides, optic tract,optic chiasm,optic nerve, anterior clinoid process, posterior clinoid process, basilar artery, P1 segment of posterior cerebellar artery are expose clearly. The straight distance from the Internal carotid artery to the optic nerve is 8.3±1.2 mm, from the posterior communicating artery to the tentorial edge is 8.1±1.7 mm, and from the anterior choroidal artery to the Posterior communicating artery is 5.6±0.9 mm。③Various anatomical triangles can distinctly exposes from the lateral wall of the cavernous sinus, among which the triangle area above the paramedieal triangle is 28.2±9.5mm2, the Parkinso's triangle area is 36.2±7.0mm2, and the Mulleu's triangle area is 19.4±5.3mm2.④Raise the temporal lobe and we can see the bottom of the temporal lobe, uncus, lateral midbrain, tentorial edge, P2 segment of posterior cerebellar artery and the superior cerebellar artery penetrates from around the oculomotor nerve and goes to the behind, and goes down the up and down part of the tentorial edge and goes around the midbrain。P2 segment of posterior cerebellar artery streches the artery of the bottom of the temporal lobe and midbrain. In this experiment, nine specimentsthe in which trochlear nerve goes around under the tentorial edge, parallels the tentorial edge in three speciments, the oculomotor nerve penetrates from between the superior cerebellar artery and the posterior cerebellar artery. Cutting the tentorial edge before the trochlear nerve initiation, we may see the trigeminal nerve and the pons, posterior toot of the trigeminal nerve, trigeminal ganglion, trochlear nerve。After grinding the temporal bone can expose the middle and upper slopes,the central section of basilar artery,and the upper pons. the lower pons can further expose after grinding the apex of temporal bone。The area of the Day rhomboid construct is 235.7±37.7mm2, and the area after the maximum grinding of the apex of temporal bone is 279.7±45.4mm2. There was a significant statistical difference in size with the t-test (P< 0.05).Conclusions①The subtemporal keyhole approach can obtain the exposure range as the traditional subtemporal approach completely. We may easily see the lateral wall of cavernous sinus, the side-saddle area, the tentorial area. And the middle and upper slopes, the middle and upper basilar artery and the upper pons after grinding the temporal bone. After the maximum grinding of the apex of temporal bone, we can further see the lower pons.②The subtemporal keyhole approach adapts to excision the glioma which gowth to the side of the hypothalamus, retrochiasmatic type craniopharyngioma, pituitary tumor, petroclival meningiomas, chordomas of opper slopes, the trigeminal nerve sheath tumor, cavernous sinus tumors,, internal carotid artery-posterior communicating artery aneurysm, and vertebrobasilar system aneurysms.③Being simple,direct and less tissue damage, the subtemporal keyhole approach can protect the superficial temporal artery and the facial nerve branches especially in the process of the flap formation. It does little damage to the temporalis, avoids the limitation of temporalis muscle block vision in the traditional subtemporal approach, reduces the Invalid exposure of brain tissue, farthest lowers the damage to the scalp, skull and adjacent tissues, avoids the damage coming from the overdue the temporal lobe stretching, and the patient can recover easily with a beautiful outward appearance.④Grind the temporal bone can remove the sheltering of the temporal bone. Seeing straight the clivus and the ventrolateral side of brainstem, the exposure of the The middle and upper petroclival region owns the absolute advantage which other approach lack。⑤The change of traveling of trochlear nerve will influence the triangle area of the paramedieal triangle and the Parkinso's triangle。However, the two general areas are relatively stead, so in the operation we can unites the two triangle gap to resect cavernous sinus tumor.