Anatomic Study Of Endoscopic Supracerebellar Transtentorial-Collateral Sulcus Keyhole Approach To The Atrium Of The Lateral Ventricle

Part I: Comparative Study of Three Surgical Approaches to the Lateral Ventricle Based on the Technique of the Magnetic Resonance ImagingBackground and objective: Accessing lesions located in the atrium of the lateral ventricle without causing a neurologic deficit can be challenging.Many surgical approaches to the atrium of the lateral ventricle have been reported,each has its advantage and disadvantage.The aim of this study was to design and verify a minimally invasive approach to the atrium named endoscopic supracerebellar transtentorial-collateral sulcus keyhole approach.The first part of this article was to perform route planning of three approaches to the lateral ventricle and compare their respective advantages and disadvantages,based on the magnetic resonance imaging technology.Methods: 10 healthy adult volunteers,received cranial magnetic resonance scanning,and then their three-dimensional(3D)brain digital models were obtained.Three simulated approaches to the choroid plexus ball in the atrium were performed in the 3D brain digital models,including the posterior parietal approach,the posterior temporal approach and the supracerebellar transtentorial approach.The operating distance and the length of cerebral cortex injury were measured respectively.And the statistical comparative analysis of the three approaches was performed.Results: The brain 3D digital model was established successfully,which could be used to simulate the surgical approach and accurately measure the distance between two points.The average operating distance of the posterior parietal approach to the atrium of the lateral ventricle was 56.54±4.56 mm,the average distance of cortical injury was 46.76±4.53 mm for the gyrus approach,and 32.37±4.25 mm for the sulcus approach;The average operating distance of the posterior temporal approach to the atrium of the lateral ventricle was 53.15±1.93 mm,the average distance of cortical injury was 42.93±2.32mm for the gyrus approach,and 22.43 ± 3.13 mm for the sulcus approach;The average operating distance of the supracerebellar transtentorial approach to the atrium of the lateral ventricle was 71.5±2.77 mm,and the average distance of cortical injury was 13.28±1.77 mm.Statistical analysis: the average operating distances of the posterior parietal approach and the posterior temporal approach were similar,no significant difference existed between the two approaches;while the average operating distance of the supracerebellar transtentorial approach was longer than the other two approaches with significant difference.There were significant differences among the cortical injury distances of the three approaches.Results showed that the cortical injury distance of the posterior parietal approach was the longest,the posterior temporal approach was the second longest,and the supracerebellar transtentorial approach was the shortest.Conclusion: Based on the magnetic resonance imaging technology,the human brain 3D digital model could be established and used to plan surgical approaches.This study showed that the operating distance of the supracerebellar transtentorial approach to the lateral ventricle was longer than the traditional surgical operations.However,the supracerebellar transtentorial approach could be a more minimally invasive approach theoretically,which possessed the shorter cortical injury distance and avoided the injury to the visual or language function.Part II: Design and Anatomic Study of the Supracerebellar Transtentorial-collateral sulcus Keyhole ApproachObjective: To observe and measure the related structures of the supracerebellar transtentorial-collateral sulcus approach,design and perform the supracerebellar transtentorial-collateral sulcus keyhole approach in cadaveric heads,and provide the anatomical basis for carrying out the approach clinically.Methods: This study was performed in 10 formalin-fixed adult cadaveric heads.Firstly,the whole brain specimens of 5 adult cadaveric heads were removed,and the collateral sulcus and the adjacent vessels were observed.The vertical distances from the posterior corpus callosum to the occipital pole were measured.Every cerebral hemisphere was cut in the coronal plane through the posterior corpus callosum,and the shortest distances from the depth of the collateral sulcus to the floor of the atrium was measured.The following structures were further observed,including the related anatomic structures about the atrium,the bridging veins in the superior cerebellar space and the tentorial sinus.Secondly,a supracerebellar transtentorial-collateral sulcus keyhole approach was performed in the other 5 head specimens.Results: The collateral sulcus has a relative constant relationship with the lateral ventricle and the optic radiation fibers cover the lateral aspect of the atrium.The lateral sulcus was a relatively constant sulcus running from front to back in base of cerebral hemisphere,which posterior part was separated with the atrium of the lateral ventricle by only one "U" cortical fiber.The medial wall of the atrium was formed by the fibers of the corpus callosum,and the lateral wall was covered by the optic radiation fibers.The choroid plexus is most developed in the atrium of the lateral ventricle.In the coronal position through the posterior corpus callosum,the mean shortest distances from the depth of the collateral sulcus to the floor of the atrium was 4.24±0.98 mm,and the mean vertical distances from the posterior corpus callosum to the occipital pole was 41.26±2.78 mm.More bridging veins from cerebellum to tentorium were located in the medial part of the tentorium,less in the middle and the lateral part.Through the supracerebellar transtentorial-collateral sulcus keyhole approach,the tapetum and the choroid plexus in the atrium was firstly observed via microscope.Next,the caudate nucleus,choroid plexus,superior wall of the lateral ventricle body could be observed furtherly,when the view angle of the microscope was moved medially.10 operations were performed successfully in the 5 cadaveric heads.Conclusions: Through the supracerebellar transtentorial-collateral sulcus keyhole approach,the middle upper part of the atrium and the posterior body of the lateral ventricle could be exposed.The present approach could be used as an available option to treat the lesions located in the atrium in selected cases.Part III: Anatomic Study of Endoscopic Supracerebellar Transtentorial-Collateral Sulcus Keyhole Approach to the Lateral VentricleObjective: In this part of the study,the endoscopic supracerebellar transtentorial-collateral sulcus keyhole approach to the lateral ventricle was performed in cadaveric head specimens.The details of the operation process were observed,summarized and discussed,to provide anatomic basis for the clinical application.Methods: 5 formalin-fixed adult cadaveric heads were scanned by magnetic resonance,and the imaging data were introduced in the neuro-navigation system.With assistance of the neuro-navigation,the endoscope was introduced into the atrium via the supracerebellar transtentorial-collateral sulcus approach in the cadaveric heads(10 hemispheres).During the procedures,the related structures were observed and the simulated operation of the lateral ventricle tumor was performed.Results: Every head was fixed in the head holder with the prone position,and the navigation registration was completed.A para-median occipital “keyhole” bone window,30 mm in diameter,was created with the transverse sinus used as the upper bound.Then the dura was opened inferior to the transverse sinus and the cerebellar hemisphere was exposed and distracted using a brain spatula.The arc tentorial incision was created about 20 mm in depth from the transverse sinus.After raising the tentorial flap,the collateral sulcus and the atrium of the lateral ventricle were visualized by the neuro-navigation.Blunt dissection through the collateral sulcus was performed and the endoscope was introduced into the atrium.After that,we could observe the atrium with a looking-up view via the endoscope.The tapetum forming a posterior part of the atrium and the choroid plexus around the pulvinar were observed firstly.The atrium opens anteriorly into the body of the lateral ventricle(medially)and into the temporal horn of the lateral ventricle(laterally).While the endoscope advanced forward in the direction of the body of the lateral ventricle,the following structures were observed: the caudate nucleus,choroid plexus,thalamus in the lateral wall,and the septa pellucidum,body of the fornix in the medial wall.Under the endoscope,the choroid plexus of the atrium and body of the lateral ventricle was removed to simulate the resection of the lateral ventricle tumor.10 operations were performed successfully in the 5 cadaveric heads.Conclusions: Through the endoscopic supracerebellar transtentorial-collateral sulcus keyhole approach,a sufficient exposure to the atrium and body of the lateral ventricle could be obtained and simulated tumor resection could be accomplished,with a minimal invasive corridor avoiding the injury to the visual or language function.This method exposes a clinical feasibility in treating the lesions located in the atrium and the posterior part of the lateral ventricle body.