| Inferior petrosal sinus (IPS) extends from the posterior part of the cavernous sinus and courses along the clivus laterally, in IPS sulcus. It usually leaves cranial cavity through the jugular foramen (JF) and eventually joins the jugular bulb (JB) or the internal jugular vein (IJV). Meanwhile, it receives one or more veins and is closely correlated with theⅥ,Ⅸ,Ⅹ,Ⅺcranial nerves on the way. With the development of microsurgery of the petro-occipital and jugular foramen regions and the application of diagnosis and therapy of skull base and cavernous sinus diseases via IJV approach, it is necessary to study the imaging anatomy of IPS, its important adjacent nerves and its anastomosis with related veins in detail. The study focused on the route of IPS, the normal and variant appearance and the confluent patterns with JB or IJV, based on thin sectional anatomy, three-dimensional reconstruction, normal or abnormal MSCT appearance of the IPS.Objective:To study the thin sectional anatomy and the imaging features of IPS and its adjacent structures, so as to provide morphological evidence and imaging reference for the diagnosis and treatment of related diseases in this region.Materials and methods:1. We observed the morphology of the IPS and its adjacent structures on the serial images chosen from the Chinese Visible Human (CVH) Data Sets (the sectioning interval was 0.1mm~0.5mm), and described and measured the diameter of the IPS in its different part. Important structures were manual segmented and reconstructed three-dimensionally.2. The subjects were 120 adult patients receiving cerebral CT angiography (CTA) in our hospital (The patients with high intracranial pressure due to cerebral tumors and other causes and patients who had heart disease were excluded). The original images were saved to Advantage Workstation (AW4.3) for slice-by-slice observation and corresponding measurement. The IPS was reconstructed with MPR, CPR and VR technology, which help to observe the IPS route, its related diameter and its confluence with other veins clearly. We also observed the morphological features of IPS on multi-slice spiral computed tomography (MSCT) images combining consecutive thin-slice sections.3. The cerebral CTA images of eight patients with high intracranial pressure due to cerebral tumors or other causes were collected. We can observe the morphological features and make corresponding measurement and discuss the effect of IPS with high intracranial pressure.Results:1. IPS was an intact venous structure which extended from the posterior part of the cavernous sinus and coursed downwards in IPS sulcus. The posterior intercavernosus sinus and basilar venous plexus (BVP) were between the left and right IPS. IPS was often divided into 1~3 branches. It left cranial cavity through the JF and eventually joined the JB or IJV after receiving tributaries. The classification of IPS-IJV junction was supplemented and further subdivided according to the level of IPS confluenced with IJV and whether there was an anastomosis with sigmoid sinus (SS).2. The initial segment, vertical segment, horizontal segment and extracranial segment of IPS could be displayed continuously on anatomical sectional images. The width of initial IPS was 5.94mm±1.34mm and 6.78mm±1.07mm on the left side and right one, the depth was 3.30mm±0.33mm and 3.23mm±0.39mm on the left side and right one; the width of vertical segment was 4.92mm±0.65mm and 5.02mm±0.75mm on the left side and right one, the depth was 2.96mm±0.42mm and 2.67mm±0.65mm on the left side and right one; the width of IPS at the point out of the cranium was 4.09mm±0.77mm and 4.25mm±0.57mm on the left side and right one, the depth was 2.95mm±0.72mm and 2.92mm±0.46mm on the left side and right one; the diameter of IPS joining JB or IJV was 2.37mm±0.93mm and 3.35mm±1.38mm on the left side and right one.3. Structures of the five representative sections of MSCT imaging corresponded with anatomical sections well. The width of initial IPS was 7.88mm±1.83mm and 8.42mm±1.87mm on the left side and right one, the depth was 2.90mm±0.83mm and 2.90mm±0.71mm on the left side and right one; the diameter of vertical segment was 1.87mm±0.82mm and 2.08mm±0.60mm on the left side and right one; the diameter of IPS at the point that left the cranium was 1.96mm±0.74mm and 1.95mm±0.68mm on the left side and right one; the diameter of IPS draining into IJV was 2.36mm±0.82mm and 2.65mm±0.85mm on the left side and right one.4. The measured results of IPS with high intracranial pressure showed as following: The width of initial IPS was 9.56mm±2.31mm and the depth was 2.39mm±0.55mm; the diameter of vertical segment was 1.76mm±0.60mm; the diameter of IPS at the point that left the cranium was 2.28mm±0.44mm and the diameter of IPS-IJV junction was 2.46mm±0.59mm.Conclusion:1. The course and variation of IPS can be revealed and traced on the serial anatomical thin-slices. The small veins and cranial nerves of skull base and the three-dimensional features of IPS were also clearly displayed. It is helpful to offer reference for sectional imaging study of IPS.2. The serial thin sectional images provided by MSCT correspond with the anatomical results well. Continuous thin-slice scanning by MSCT in combination with MPR, CPR and VR can clearly show the route of IPS and its confluence with relevant veins. So, MSCT is an accurate technique of imaging for evaluating morphological features of IPS.3. MSCT has high spacial resolution and can reveal the small veins clearly. Combining with continuous thin slice, the IPS-IJV junction was further subdivided according to the level of IPS confluence with IJV and whether there is an anastomosis with SS. Meanwhile, we found the lower IPS-IJV junction is also a common type, and might be used as an alternative access to the intra-cranial IPS. MSCT is helpful for showing the route and variation of IPS, and can be used as an effective method for preoperative evaluation of IPS.4. There are some morphologic changes of IPS in a certain degree when intracranial pressure increased. Although we have not enough samples in this experiment, the results still have some clinical value for subsequent research. |
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