الفهرس 
INTRODUCTION AND AIM OF THE WORKOnly 14 pages are availabe for public view
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Abstract
Magnetic resonance (MR) imaging is the method of choice to evaluate the cranial nerves. Although the skull base foramina can be seen on CT, the nerves themselves can only be visualized in detail on MR. All cranial nerves are paired and therefore it is wise to compare size and signal intensity of both nerves. The coronal plane is best suited to study the cranial nerves I to VI, as they have a dominant postero-anterior course. Cranial nerves VII to XII run in an antero-lateral-caudal direction but the lateral component is dominant. MR imaging has become the modality of choice in evaluating cranial nerve integrity. Although CT is still beneficial to evaluate the bone canals and foramina, petrous temporal bone, and certain regions of the neck, MR imaging allows detailed evaluation of the anatomy and pathology of the brainstem, and nerves can now be better defined and characterized. On 3D-CISS images, the arteries and the nerves were shown as structures with low signal intensity, and the CSF was shown as a structure with high signal intensity, thus providing high contrast resolution between them. The cisternal segment of CN IX, X, XI complex were identified with certainty in 100% obtained in oblique axial planes, in 99% obtained in oblique sagittal planes; hypoglossal nerves were identified with certainty in 90% obtained in oblique axial planes, in 91% obtained in oblique sagittal planes. 3D-FIESTA imaging after intravenous administration of gadodiamide hydrate contrast to demonstrate the normal anatomy of the intraforaminal and canalicular portions of cranial nerves IX–XII. The reproducibility and consistency in demonstrating the distinct anatomic courses of cranial nerves IX–XII of contrast enhanced 3D-FIESTA MR imaging in vivo makes this technique potentially useful in the evaluation of the extent of cranial nerve involvement by tumors. As radiologic imaging technology improves and more intricate details of the anatomy can be evaluated, images provide more precise diagnostic information and allow better localization of abnormalities. For example, standard T2-weighted magnetic resonance (MR) imaging sequences adequately depicted only the larger cranial nerves, whereas current steady-state free precession (SSFP) sequences are capable of depicting the cisternal segments of all 12 cranial nerves. SSFP sequences provide submillimetric spatial resolution and high contrast resolution between cerebrospinal fluid and solid structures, allowing the reconstruction of elegant multiplanar images that highlight the course of each nerve. Three-dimensional (3D) constructive interference in steady state (CISS) MR imaging is useful for demonstrating cranial nerves (CNs) in the cistern. The detection of individual cranial nerves in the intraforaminal portion of the jugular foramen and hypoglossal canal is useful in diagnostic imaging1; however, visualization by using conventional MR imaging protocols does not provide adequate detail of individual nerves.2,3. Recently, contrast enhanced 3D constructive interference in steady state (CISS) MR imaging has successfully demonstrated the trigeminal ganglion and its divisions and individual cranial nerves within the cavernous sinus.4,5 3D fast imaging employing steady-state acquisition (FIESTA) is a similar form of steady-state sequence MR imaging. Evidence has shown a proportional increase in contrast between the background structures and the cranial nerves within the cisterns as the concentration of gadolinium-based contrast agent increases with 3D steady-state imaging sequences. The cisternal segments of the lower cranial nerves (CNs) adjacent to the jugular foramen (JF) are difficult to identify reliably by routine MR imaging. We performed a 3D balanced fast-field echo imaging technique (3D-bFFE) to obtain detailed anatomy of the cisternal segments of CNs IX, X, and XI. With the use of traditional MR imaging pulse sequences, it may be difficult to evaluate the cisternal segments of the cranial nerves, which are small in diameter and are located in close proximity to many other anatomic structures. So we recommend the FIESTA (fast imaging employing steady state of acquisition) technique which depict these nerve segments in greater detail and can provide important information about the relationship of the nerves to pathologic processes. To take full advantage of this information, radiologists must be familiar with the expected nerve anatomy and relevant anatomic landmarks.