Study On Microsurgery Anatomy Of The Combination Approach In Subtemporal-occipital And Posterior Sinus Sigmoideus

Objective Surgical access to lesions of petroclival region represents a challenge, both because of the depth of the lesion site and the vicinity of complex neurovascular structures. Maximal exposure of the lesion with minimal approach-related complication is the most important problem to deal with in the microsurgery of these lesions. For this, accurate knowledge of the surgical anatomy of this region is mandatory, and the reasonable choice of type of approach is based on the location of lesion, preoperative neurological deficit. Through studying the feature of neurovascular in petroclival region, we simulated the combination of subtemporal-occipital and posterior sinus sigmoideus approach. To aggregate analysis the typical surgical approaches at present, we consume this approach can preferbly expose the lesions in petroclival region, lower the para-trauma, and worth clinical generalization.Methods Ten formalin-fixed human adult cadaveric heads were divided into two groups. Five heads in each group. Arteries were injected with red silicone in all heads and veins injected with blue silicone. The first group: we measured the anatomic struture of petroclival region and cerebellopon angle, and analyzed the measured data statistically. The second group: we simulated the combination of subtemporal-occipital and posterior sinus sigmoideus approach and make a summary of the gains from learning the surgical approach. Results The length of anterior margin of foramen magnum to dorsum sella was 3916±315mm (2914-5011mm), and anterior margin of foramen magnum was located in the two mastoidales. The distance between two mastoidales was 1216±218mm (716-1518mm). The length of temporal-petrous pyramid was 4818±218mm. PCA was near to the free margin of cerebellum tentorium. SCA can contact withⅢ,Ⅳ,Ⅴ. Trigeminal nerve can be moved downwards and forth after drilling the bone of apex of petrous bone lateral inferior to trigeminal ganglion. Petrosa ligament was a useful signal to identify the abducent nerve. AICA contacts withⅤ,Ⅵ,ⅦⅧand the relationship between AICA andⅦⅧis most complex. The course of basilar artery (BA) has great variation and gives off perforating arteries to supply lateral or ventral pons in each segment. The course and origin of PICA is most complex and it can contacts withⅦ,Ⅷ,Ⅸ,Ⅹ,ⅪandⅫand the relationships between it andⅨ,Ⅹ,Ⅺare most complex. The perforating arteries of BA arise from the posterior wall of BA to supply ventral medulla and BA gives off anterior spinal artery BA may contacts withⅫ. The maximum pull-angel of cerebellar was 61°.Conclusion①This investigation proved that the combination of subtemporal occipital and posterior sinus sigmoideus could decurtate time of surgery. By cuting-off tentorium of cerebellum, sup-tentorium communicate to infer-tentorium, and it dose not have to deal with too much petrous apex. They are superior to the traditional approaches in the extent of exposure, working distance and angle of visualization, moreover lower the dangerous which can damage patients acouesthesia. This surgical approach can do well to the lesions of petroclival resion and is worth to be recommended.②Because there are reasonable potential danger of injury to important structures in many steps in this approach, specific important structures should be exposed or resected as like stripping scope of petrous apex, the angel of lobus temporalis was raised , the level of cerebellar was pulled needed to maximize the exposure while minimize the complication.③The surgical anatomy of petroclival region is complex. Systemic knowledge of neurovascular structures anatomy in this area and extensive training are mandatory for mastering these modern skull-base approaches.