Clinical Anatomy And Three Dimensional Visualization Of Petrous Pyramid And Its Adjacent Structures

Part 1 Microanatomy and topographic anatomy of petrous pyramid and its adjacent structuresObjectiveTo explore applying microanatomy and topography to commonly the anatomical structures of the region of petrous pyramid and its adjacent organs, those could conduce to identify anatomical relationship themselves and could provide the related surgical operation of the region of petrous pyramid,clivus and cerebellopontine angle(CPA) with morphologic data.MethodsTwenty sides of 10 adult cadaveric heads were dissected under the microscope to simulate the retrosigmoid approach(RS).The CPA was entered to expose the neurovascular structures,and the internal auditory canal was opened by drilling the margin of the internal auditory meatus.After surgery,the cadaveric heads were dissected by topography.we could observe the adjacent spatial relationship of some important structures,such as trigeminal ganglion and its branches,superficial greater petrosal nerve(SGPN),internal carotid artery(ICA),foramen spinosum(FS),foramen ovale(FO) and arcuate eminence as well in the base of middle cranial fossa and could reveal the feature of neurovascular pathway in the CPA.Simultaneously the related structures were measured in the CPA based on the junction of the superior petrosal sinus and sigmoid sinus(JSPS) and internal acoustic pore(IAP).And some related structures were also measured in the petrous bone. ResultsAccording to anatomical position,the CPA cistern is divided with the anterior compartment,the middle compartment,the posterior compartment under the microscope built on the anatomical marker of the acoustic- facial bundle(AFB) and glossopharyngeal nerve.However,abiding by RS approach,the structures in the CPA are observed from shallow to deep and the CPA cistern is divided with the posterior compartment,the middle compartment,the anterior compartment gradually.In the course of RS approach,the posterior wall of internal acoustic meatus is stripped and those internal structures in the internal acoustic meatus are displayed.Thus,the anatomical structures of CPA are full exposed.The related structures are measured in the CPA based on the JSPS and internal acoustic pore.These part results are as follows:The averaged distance from the JSPS to the trigeminal nerve,the AFB,glossopharyngeal nerve,hypoglossal nerve,Dorello's canal,vagus nerve,vestibular aqueduct are(38.50±2.64)mm,(27.8±2.25)mm,(32.70±2.11)mm,(44.30±2.05)mm, (48.23±3.25)mm,(34.23±2.56)mm,(20.01±3.69)mm and the averaged distance from IAP to the trigeminal nerve,abducent nerve,tentorium of cerebellum,glossopharyngeal nerve,vagus nerve,vestibular aqueduct, hypoglossal nerve are(5.68±1.55)mm,(13.80±1.81)mm,(5.00±0.66)mm, (6.34±1.24)mm,(8.49±1.68)mm,(10.34±1.33)mm,(20.79±1.93)mm.Besides,after surgery,the cadaveric heads are dissected by topography in the petrous bone of the base of middle cranial fossa.We found trigeminal ganglion is encased in two parts of cerebral dura maters.The first above trigeminal ganglion also have two parts of cerebral dura maters,however,the second below trigeminal ganglion have only one.Moreover,the surface of trigeminal ganglion coated tunica vaginalis of nerve that was formed by arachnoid.After removed trigeminal nerve,we find foramen lacerum is below trigeminal ganglion.The spatial relation of trigeminal nerve,ICA,foramen lacerum(FL), SGPN,FS,FO,the lateral wall of cavernous sinus are close.At the same time, these vital structures are observed and surveyed,the part results as follows: the averaged distance from hiatus for greater superficial petrosal nerve to intersection between SGPN and trigeminal nerve,FS,superior petrosal sinus, the apogee of arcuate eminence are(11.88±1.99)mm,(11.2±2.11)mm,(11.9±2.26)mm,(13.36±2.6)mm;the averaged distance from the root of trigeminal nerve to foramen rotundum(FR),FO,FS,the apogee of arcuate eminence and the inlet of trochlear nerve entering tentorium of cerebellum(TC) are (23.85±1.77)mm,(18.91±1.88)mm,(19.15±1.29)mm,(23.22±1.96)mm, (4.92±1.22)mm;The width and height of Meckel's cave are(10.38±1.11)mm, (4.27±0.63)mm respectively;the averaged distance from intersection between SGPN and trigeminal nerve to FS,ridge of petrosal bone,the apogee of arcuate eminence are(5.84±1.03)mm,(11.84±1.69)mm,(24.75±2.3)mm;and the averaged distance from the apogee of arcuate eminence to FS,posterior clinoid process,internal acoustic pore,the inlet of trochlear nerve entering TC are(25.46±2.43)mm,(41.57±2.89)mm,(17.33±2.43)mm,(29.4±1.99)mm;the averaged distance from FS to inferior margin of foramen lacerum is (8.62±2.75)mm;the averaged distance from the inlet of trochlear nerve entering TC to posterior clinoid process is(11.7±2.51)mm.ConclusionsThe CPA is divided into the anterior compartment,the middle compartment, the posterior compartment under the microscope.Those are helpful to understand the feature of the neurovascular layer in the CPA.The related structures are measured based on the JSPS and IAP,those are helpful to quantization of the related structures and to judge whether each compartment is deep or shallow and is big or small in the CPA.Thus those benefit microsurgery in the CPA.Recognizing the anatomical marker of IAP supports preservation of the inner structures in the internal auditory meatus under microsurgery.Applied topographic technique to observe and survey the important structures of petrous bone,these could quantify their anatomical and spatial relationship and could provide surgical operation of related petrous pyramid with morphologic data.In conclusion,by integrating microanatomy and topography,we could have a comprehensive knowledge about the anatomical relation of the region of petrosal pyramid,clivus and CPA.Part 2 Virtual anatomy of retrosigmoid approach and medical image fusion and reconstruction of the petrous pyramidObjectiveThrough computer image fusion and virtual reality technology,for one thing, discussing simulation of the retrosigmoid approach by use of CT,MR fusion image is to provide a new methods and supplementary information about the anatomical training and surgical planning in the surgery of the skull base;for another,exploring multimodality image registration,fusion and 3-D reconstruction about petrous pyramid,internal carotid artery and bony labyrinth is to provide preoperative design and simulation of skull base surgery with morphologic basis.Methods Firstly,the CT and MRI data of 10 patients' head were input to the workstation of Dexotroscope system,corresponding works were executed including segmentation,registration,fusion,3-D reconstruction,and simulation of every step of the RSA in the environment of virtual reality.Besides,these data were input to the Excelim-04 neurosurgery navigation system that was researched by the digital medical research center of Fudan University,corresponding works were executed including registration and fusion.Skull base and bony labyrinth were reconstructed based on CT image of petrous pyramid,internal carotid artery was reconstructed built on MRA image.Accordingly, multistructures are displayed in the same image at the same time by using the Excelim-04 neurosurgery navigation system.ResultsDexotroscope system clearly displays asterion,the angle of the transverse and sigmoid sinus,jugular foramen,internal acoustic pore,basilar artery and its branches,and their spatial relationship are observed.Meanwhile,the reconstructed image of petrous pyramid,internal carotid artery and bony labyrinth could be clearly displayed with one or multi-structures by the Excelim-04 neurosurgery navigation system.Their position and relationship are distinguished by different pseudo-color and transparency.They could also be rotated,observed in any direction based on skull base surgery.ConclusionsAfter clinical CT,MRI of head are input to the workstation of Dexotroscope system,virtual reality of Dexotroscope system can rapidly,wholly fuse all kinds of medical data and can display individually local anatomical structure. Similarly,after using the Excelim-04 neurosurgery navigation system, registration,fusion and 3-D reconstruction of clinical CT,MRI of head could also be accomplished rapidly,and the system could clearly display skull base, bony labyrinth and internal carotid artery.The two kinds of techniques could carry out medical image fusion,3D reconstruction of CT and MR data of the head and also could execute individually preoperative diagnosis and surgical planning.Differently,virtual reality technique of Dexotroscope system can conduct simple interaction by surgeon and can real-time simulate the surgical approach and virtual anatomy,therefore,the Dexotroscope system should belong to surgical training.The fusion image can be applied to intraoperation by the Excelim-04 neurosurgery navigation system.It should belong to intraoperative guidance.Accordingly,the two kinds of techniques could provide a kind of new,valid and supplementary method for anatomical training, surgical planning,image-guided surgery of skull base surgery.