Study On Applied Anatomy Of The Presigmoid Retrolabyrinthine Approach

Petroclival region is deep, and adjacent structures are complex and important, the slope region is the site that the tumors often happen, the region also is difficult to treat by operation in neurosurgery. In recent decades, Morrison, Hakuba, Sekhar, Al-Mefty, Horgan etc.made prominent contributions in surgical approach of petrous bone and slope , they explained anatomical relationships of petroclival region, and designed some important surgical approaches. However, to explore the best treatment of diseases of petroclival region is constantly the focal questiones, the core need approach ,which can make visual field of surgery wider, distance of operations shorter and pulling of brain lighter.The petrous bone approach can provide well surgical exposure to the focus of infection in petroclival and posterior part of the cavernous sinus, presigmoid approach is the most representative approach of petroclival region. According to the level of inner ear stripping, The petrous bone approach has four subtypes: retrolabyrinthine approach, resection of the labyrinthine approach, labyrinth approach and cochlear approach. Retrolabyrinthine approach is simple, does not cause damaged of vestibular nerve and cochlear nerve generally. But the labyrinthus osseus can block fields in operation, especially when sigmoid sinus forward or abnormal thickening, it is difficult to expose petroclival fully. Resection of labyrinthine approach grinded anterior semicircular canal and posterior semicircular canal on the level btween ampulla and common crus, cut the apex of petrous bone, provided larger space for operation, most of patients can reservations hearing. The labyrinth and the cochlear approach may result in permanent hearing loss, and more complications, therefore, application of it was less in clinical.Petrosal bone has many important structural, and the position often changes, so clinical applications are faced great difficulties. Petroclival is adjacent to the pons and the ventral of medulla oblongata,Ⅴ~Ⅻcranial nerves, internal carotid artery, basilar artery, jugular bulb and cavernous sinus, the relationships are complicated, cause of the observation of surgical microscope is linear, certain location and angle cannot be see, and is difficult to observe facial nerve root and surrounding tissue blocked by the acoustic nerve and cerebellum Rongqiu directly, these have greatly restricted the clinical application of it.Grinding the posterior temporal bone is a key in operation through the presigmoid approach passed petrous bone, and it is necessary to expose the field well, and avoid any injury of important structures. The difficulty is location and protection of the facial nerve canal and posterior semicircular canal. At present researches are rare in the grinding of petrous bone, the protection of facial nerve canal and semi-regulatory, choice of cranial nerve reasonably, space of vascular.Objective: To observe and measure the structures of the temporal bone and the space of petroclival, and provide reliable basises for grinding security operation in the petrous bone and expand petroclival exposure of the operative field. We provide anatomical information for petrous bone posterior approach. Methods:The anatomy of transpetrosapostlabyrinthine presimoid approach in the adult cadaveric head specimen was studied. The anatomical structure of different layers was observed. Marked the external auditory canal spine, and measured the distance from it to the anterior wall of sigmoid sinus anterior spine, sigmoid sinus-shaped transverse sinus, posterior wall of posterior semicircular canal and facial nerve canal, also measured area of the gap between cranial nerve and trigeminal nerve, and the gap of facial nerve and glossopharyngeal nerve.Results:①The left distance from the anterior wall of sigmoid sinus anterior spine to external auditory canal spine was 17.72±1.09mm, the right was 18.51±1.00mm;②The left distance from sigmoid sinus-shaped transverse sinus to the external auditory canal spine was 33.81±3.16mm, the right was 30.28±5.88mm;③The left distance from the posterior wall of posterior semicircular canal to the external auditory canal spine was 13.17±0.31mm, the right was 12.79±0.59mm;④The left horizontal distance from posterior wall of facial canal to the the external auditory canal spine was 7.90±0.44mm, the right was 7.78±0.94mm;⑤The distance of intracranial trigeminal nerve: left is 15.01±0.53mm, right is 1.446±0.31mm; the distance of intracranial facial and acoustic nerve : left is 23.58±1.00mm, right is 25.06±1.05mm; the distance of intracranial glossopharyngeal nerve: left is 18.36±0.97mm, right is 19.89±0.51mm;⑥The vertical distance from the point that trigeminal nerve out of the brain to facial and acoustic nerve: left is 8.68±0.58mm, right is 9.85±0.49mm; the vertical distance from the point that facial and acoustic nerve out of dura mater to trigeminal nerve: left is 11.52±0.66mm, right is 10.89±0.69mm; the vertical distance from the point that facial and acoustic nerve out of the brain to glossopharyngeal nerve: left is 8.36±0.65mm, right is 7.89±0.75 mm; the vertical distance from the point that glossopharyngeal nerve out of dura mater o to facial and acoustic nerve: left is 6.48±0.71mm, right is 7.82±0.56mm;⑦The left area beween trigeminal nerve to facial nerve was 236.56±2.06 mm2, the right was 222.83±1.86 mm2; the left area beween facial nerve to glossopharyngeal nerve was 156.31±2.86 mm2, the right was 187.76±2.37 mm2.Conclusion:The line between anterior angle of parietomastoid suture and external occipital protuberance marked transverse sinus. the line between anterior angle of parietomastoid suture and mastoidale marked sigmoid sinus. The anterior angle of parietomastoid suture marked the crosspoint between petrosal sinus and sigmoid sinus. When drilling the hole of the skull,the asterion shuold be centre. The four holes were radialis, and the points on the sides of the transverse sinus. The two point near mastoid portion were near the sino- membrane angle. This selection can protect the venous sinuses. The difficult parts about stripping pyramis ossis temporalis were to locate and protect posterior semicircular cana and canalis facialis. The allocation of the protect posterior semicircular cana was according to the density of os petrosum, with the sclerotic mastoid lateral semicircular canal can allocate posterior semicircular cana. In the search for the facial nerve canal, bone labyrinth, it is necessary to make the external auditory canal spine as a symbol. CT and MRI about head should be test, and observe location of sigmoid sinus, such as pre-sigmoid sinus forward, the choice is not recommended to operate transpetrosapostlabyrinthine presimoid approach.The gap between trigeminal nerve and facial nerve and the gap between t facial nerve and glossopharyngeal nerve are larger than others, they are the good space for the operation.