The Study Of Microsurgical Anatomy Of The Jugular Foramen

Objective To understand the microsurgical anatomy and the surgical approach of the jugular foramen and to provide anatomical basis for the operation of the region.Methods (1) Direct foraminal measurements were made in twenty dry skulls (40 sides),and the relationship of these foramina to each other and various landmarks were determined in the jugular foramen and the adjacent bone structures .(2) Ten adult cadaveric heads (20 sides) fixed in 10% formalin were examined using microsurgical techniques and instruments, including the operating microscope. Lateralposterior approaches and modified approaches were selected to study. The anatomic relationships of the muscles, nerves, arteries and veins were carefully recorded, with special emphasis regarding the relative relationship of these structures.Results 1. The jugular foramen was located between the petrouspart of the temporal bone and occipital bone. The jugular forame was divided into anterior medial portion and posterior lateral portion. The right jugular forame was usually larger than the left. 2. The tympanomastoid notch was situated lateral to stylomastoid foramen, which the distance was 12.26±2.14mm. 3. The shortest distance from the tragal pointer to the trunk of facial nerve was 9.60+1.64mm. 4. At the intracranial orifice of the jugular forame, the dural forms the glossopharyngeal meatus through which the glossopharyngeal nerve passed, and the vagal meatus through which the vagus and accessory nerves passed. At the extracranial orifice of the jugular forame, the neural compartment was in anteromedial.The inferior petrosal sinus entered the foramen between CNs IX and X in most cases. 5.The hypoglossal nerve and the vagus nerve were closed below the level of the transverse process ofthe atlas. The hypoglossal nerve departed from the vagus nerve at the extracranial orifice of The jugular forame. CNsX,XI and XII were contacted tightly between the extracranial orifice of The JF and TPA. 6.The third segments of the vertebral artery was located in the medial of the obliquus capitis superior.There were much vertebral venous plexus which surrounding vertebral artery.Conclusions l.The tragal pointer and The tympanomastoid notch are two key landmarks to identify the extratemporal segment of the facial nerve. 2.The situation of TPA is invariable, which is a useful anatomic landmark to upper cervical region; TPA and rectus capitis lateralis are reliable borderline of parapharyngeal space and suboccipital triangle. 3.It is important to identify comparative situation of nerves and vessels in JF region; It is unclear and unimportant to divide the JF into two or three compartments. 4.The glossopharyngeal nerve comes out from the JF with fascia singly and has space to the other three cranial nerves. The other three cranial nerves can be protected when tumor involving the glossopharyngeal nerve is removed. 5.1t is a effective measure through removing the jugular process of occipital bone and exposing the horizontal segment of the sigmoid sinus to widen operation yield from backside and to control hemorrhage. 6.1t is important for protecting the vertebral artery to insure the integrality of obliquus capitis superior and obliquus capitis inferior.