The jugular foramen: imaging strategy and detailed anatomy at 3T

Computed tomographic features of canine intracranial and jugular foraminal masses involving the combined glossopharyngeal, vagus, and accessory nerve roots

A chronic cough, gag, or retch is a common presenting clinical complaint in dogs. Those refractory to conservative management frequently undergo further diagnostic tests to investigate the cause, including CT examination of their head, neck, and thorax for detailed morphological assessment of their respiratory and upper gastrointestinal tract. This case series describes five patients with CT characteristics consistent with an intracranial and jugular foraminal mass of the combined glossopharyngeal (IX), vagus (X), and accessory (XI) cranial nerves and secondary features consistent with their paresis. The consistent primary CT characteristics included an intracranial, extra-axial, cerebellomedullary angle, and jugular foraminal soft tissue attenuating, strongly enhancing mass (5/5). Secondary characteristics included smooth widening of the bony jugular foramen (5/5), mild hyperostosis of the petrous temporal bone (3/5), isolated severe atrophy of the ipsilateral sternocephalic, cleidocephalic, and trapezius muscles (5/5), atrophy of the ipsilateral thyroarytenoideus and cricoarytenoideus muscles of the vocal fold (5/5), and an ipsilateral "dropped" shoulder (4/5). Positional variation of the patient in CT under general anesthesia made the "dropped" shoulder of equivocal significance. The reported clinical signs and secondary CT features reflect a unilateral paresis of the combined cranial nerves (IX, X, and XI) and are consistent with jugular foramen syndrome/Vernet's syndrome reported in humans. The authors believe this condition is likely chronically underdiagnosed without CT examination, and this case series should enable earlier CT diagnosis in future cases.

Jugular Foramen Syndrome Caused by Varicella Zoster Virus Infection

Jugular foramen syndrome (JFS) is a lower cranial neuropathy syndrome characterized by dysphonia and dysphagia. The syndrome is caused by dysfunction of the glossopharyngeal, vagus, and spinal accessory nerves at the level of the pars nervosa and pars vascularis within the jugular foramen. There are numerous etiologies for JFS, including malignancy, trauma, vascular, and infection. Here, we present the case of a healthy adult man who developed JFS secondary to an atypical presentation of Varicella Zoster meningitis, and was promptly diagnosed and treated with rapid symptom resolution. We diagnosed the patient using specialized skull-based imaging which detailed the jugular foramen, as well as CSF analysis. This case highlights the clinical value of detailed structural evaluation, consideration for infection in the absence of systemic symptoms, and favorable outcomes following early identification and treatment.

ACR Appropriateness Criteria® Cranial Neuropathy: 2022 Update

Cranial neuropathy can result from pathology affecting the nerve fibers at any point and requires imaging of the entire course of the nerve from its nucleus to the end organ in order to identify a cause. MRI with and without intravenous contrast is often the modality of choice with CT playing a complementary role. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer-reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer-reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Magnetic resonance neurography of the head and neck: state of the art, anatomy, pathology and future perspectives

Magnetic resonance neurography allows for the selective visualization of peripheral nerves and is increasingly being investigated. Whereas in the past, the imaging of the extracranial cranial and occipital nerve branches was inadequate, more and more techniques are now available that do allow nerve imaging. This basic review provides an overview of the literature with current state of the art, anatomical landmarks and future perspectives. Furthermore, we illustrate the possibilities of the three-dimensional CRAnial Nerve Imaging (3D CRANI) MR-sequence by means of a few case studies.

Cranial nerve schwannoma - A pictorial essay

Schwannomas are peripheral nerve sheath tumours arising from cranial, spinal or peripheral nerves. Most of the schwannomas are benign with the rare possibility of malignant transformation. Cranial nerve schwannomas can be seen along the course of any cranial nerve in the intracranial region or head and neck location. Although a majority are solitary sporadic lesions, multiple schwannomas can be seen in syndromes like neurofibromatosis type 2 and rarely in type 1. Since intracranial schwannomas are slow-growing, clinical presentation varies between no symptoms to cranial nerve palsy. Most of the times, the symptoms are due to mass effect over the adjacent structures, foraminal widening, compression of other cranial nerves, denervation injury or hydrocephalus. Familiarity with the course of the cranial nerves, imaging appearances and clinical presentation of schwannomas helps in accurate diagnosis and possible differential diagnosis, especially in uncommon clinical and radiological appearances. In this pictorial review, we illustrate relevant anatomy of cranial nerves, imaging features of schwannomas of most of the cranial nerves, clinical presentation and differential diagnosis.

Isolated Hypoglossal Nerve Palsy Due to an Osteophyte with Atlantoaxial Dislocation

Isolated hypoglossal nerve palsy (IHP), or hypoglossal nerve palsy without any other neurological signs, is rare. We report a woman with atlantoaxial dislocation (AAD) who presented with IHP due to hypoglossal nerve compression by an osteophyte at the hypoglossal canal. A 77-year-old woman presented with speech difficulties and the feeling of a swollen tongue on the left side for 3 days. Her only neurological feature was left hypoglossal nerve palsy. She had been diagnosed with AAD 2 years before. Computed tomography (CT) and high-resolution magnetic resonance imaging (MRI) revealed the compression of the basicranial hypoglossal nerve at the external orifice of the hypoglossal canal by an AAD osteophyte which was causing IHP. IHP can develop due to hypoglossal nerve compression by an osteophyte from AAD. CT and high-resolution MRI revealed this rare mechanism of IHP.

Technical Improvements in Head and Neck MR Imaging: At the Cutting Edge

Head and neck MR imaging is technically challenging because of magnetic field inhomogeneity, respiratory and swallowing motion, and necessity of high-resolution imaging to trace key anatomic structures. These challenges have been answered by advances in MR imaging technology, including isovolumetric three-dimensional imaging, robust fat-water separation techniques, and novel deep learning-based reconstruction algorithms. New applications of MR imaging have been advanced and functional imaging has been improved. Improvements in acquisition and reconstruction technique facilitate novel applications of morphologic and functional imaging. This results in opportunities to improve diagnosis, staging, and treatment selection through application of advanced MR imaging techniques.

Normal Anatomy of Cranial Nerves III–XII on Magnetic Resonance Imaging

복잡한 해부학적 구조와 기능 때문에 뇌신경 질환의 신경영상검사는 항상 어려운 과제이다. 최근 자기공명영상(이하 MRI) 기법의 발달로 많은 경우에서 뇌신경 질환의 원인이 규명되고 있으며, 신경영상의학 의사들은 다학제 팀의 핵심적 팀원으로서 다양한 뇌신경 질환의 원활한 진단을 위하여 MRI에서 관찰되는 뇌신경의 세밀한 해부학적 구조를 잘 알아야 한다. 이 종설에서는 말초성 뇌신경 III–XII에 대해 뇌간으로부터 두개 밖까지 해부학적으로 비슷한 구조를 가지는 구역별로 분류하여 각 구역에서 보이는 뇌신경의 정상 해부학 및 MRI 소견을 설명하고자 한다. 또한 각 구역에서 가장 적합한 MRI 기법에 관하여도 기술하고자 한다.

Tracking the glossopharyngeal nerve pathway through anatomical references in cross-sectional imaging techniques: a pictorial review

Abstract

The glossopharyngeal nerve (GPN) is a rarely considered cranial nerve in imaging interpretation, mainly because clinical signs may remain unnoticed, but also due to its complex anatomy and inconspicuousness in conventional cross-sectional imaging. In this pictorial review, we aim to conduct a comprehensive review of the GPN anatomy from its origin in the central nervous system to peripheral target organs. Because the nerve cannot be visualised with conventional imaging examinations for most of its course, we will focus on the most relevant anatomical references along the entire GPN pathway, which will be divided into the brain stem, cisternal, cranial base (to which we will add the parasympathetic pathway leaving the main trunk of the GPN at the cranial base) and cervical segments. For that purpose, we will take advantage of cadaveric slices and dissections, our own developed drawings and schemes, and computed tomography (CT) and magnetic resonance imaging (MRI) cross-sectional images from our hospital’s radiological information system and picture and archiving communication system.

Teaching Points

• The glossopharyngeal nerve is one of the most hidden cranial nerves.

• It conveys sensory, visceral, taste, parasympathetic and motor information.

• Radiologists’ knowledge must go beyond the limitations of conventional imaging techniques.

• The nerve’s pathway involves the brain stem, cisternal, skull base and cervical segments.

• Systematising anatomical references will help with nerve pathway tracking.

Advances in the Study of the Middle Cranial Fossa through Cutting Edge Neuroimaging Techniques

The objective of this paper is to present a morphometric study of the middle cranial fossa from the study of 87 patients using cutting edge multislice computed tomography scans (32 detectors) and Magnetic Resonance Imaging. The study presents a detailed anatomical-radiological and morphometric analysis of the middle cranial fossa as well as its neurovascular elements in normal conditions. The implications of this investigation in training and clinical contexts are discussed.

Visualization of Cranial Nerves Using High-Definition Fiber Tractography

BACKGROUND

Recent studies have demonstrated diffusion tensor imaging tractography of cranial nerves (CNs). Spatial and angular resolution, however, is limited with this modality. A substantial improvement in image resolution can be achieved with high-angle diffusion magnetic resonance imaging and atlas-based fiber tracking to provide detailed trajectories of CNs.

OBJECTIVE

To use high-definition fiber tractography to identify CNs in healthy subjects and patients with brain tumors.

METHODS

Five neurologically healthy adults and 3 patients with brain tumors were scanned with diffusion spectrum imaging that allowed high-angular-resolution fiber tracking. In addition, a 488-subject diffusion magnetic resonance imaging template constructed from the Human Connectome Project data was used to conduct atlas space fiber tracking of CNs.

RESULTS

The cisternal portions of most CNs were tracked and visualized in each healthy subject and in atlas fiber tracking. The entire optic radiation, medial longitudinal fasciculus, spinal trigeminal nucleus/tract, petroclival portion of the abducens nerve, and intrabrainstem portion of the facial nerve from the root exit zone to the adjacent abducens nucleus were identified. This suggested that the high-angular-resolution fiber tracking was able to distinguish the facial nerve from the vestibulocochlear nerve complex. The tractography clearly visualized CNs displaced by brain tumors. These tractography findings were confirmed intraoperatively.

CONCLUSION

Using high-angular-resolution fiber tracking and atlas-based fiber tracking, we were able to identify all CNs in unprecedented detail. This implies its potential in localization of CNs during surgical planning.

ABBREVIATIONS

CN, cranial nerveDSI, diffusion spectrum imagingDTI, diffusion tensor imagingHCP, Human Connectome ProjectHDFT, high-definition fiber tractographyMLF, medial longitudinal fasciculusODF, orientation distribution functionROI, region of interest.

Complete morphometric analysis of jugular foramen and its clinical implications

INTRODUCTION

Tumors affecting structures in the vicinity of jugular foramen such as glomus jugulare require microsurgical approach to access this region. These tumors tend to alter the normal architecture of the jugular foramen by invading it. Therefore, it is not feasible to have correct anatomic visualization of the foramen in the presence of such pathologies. Hence, a comprehensive knowledge of the jugular foramen is needed by all the neurosurgeons while doing surgery in this region.

AIM

Due to the inadequate knowledge of the accurate morphology of the jugular foramen in different sexes, the aim of this osteological study was to provide a complete morphometry including gender differences and describe some morphological characteristics of the jugular foramen in an adult Indian population.

MATERIALS AND METHODS

The study was done on 114 adult human dry skulls (63 males and 51 females) collected from the osteology museum in the department. Various dimensions of both endo- and exocranial aspect of jugular foramen were measured. Presence and absence of domed bony roof of jugular fossa and compartmentalization of jugular foramen were also noticed. Statistical analysis was done using Chi-square test and Student's t-test in SPSS version 23.

RESULTS

All the parameters of right jugular foramen were greater than the left side, except the distance of stylomastoid foramen from lateral margin of jugular foramen (SMJF) which was greater on the left side. Gender differences between various measurements of jugular foramen, presence of dome of jugular fossa, and compartmentalization patterns were reported.

CONCLUSION

This study gives knowledge about the various parameters, anatomical variations of jugular foramen in both sexes of an adult Indian population, and its clinical impact on the surgeries of this region.

Role of targeted magnetic resonance imaging sequences in the surgical management of anterior skull base pathology

BACKGROUND

The skull base is a highly complex anatomical region that provides passage for important nerves and vessels as they course into and out of the cranial cavity. Key to the management of pathology in this region is a thorough understanding of the anatomy, with its variations, and the relationship of various neurovascular structures to the pathology in question. Targeted high-resolution magnetic resonance imaging on high field strength magnets can enable the skull base surgeon to understand this intricate relationship and deal with the pathology from a position of relative advantage.

OBJECTIVE

With the help of case studies, this paper illustrates the application of specialised magnetic resonance techniques to study pathology of the orbital apex in particular.

CONCLUSION

The fine anatomical detail provided gives surgeons the ability to design an endonasal endoscopic procedure appropriate to the anatomy of the pathology.

Fast imaging employing steady-state acquisition (FIESTA) MRI to investigate cerebrospinal fluid (CSF) within dural reflections of posterior fossa cranial nerves

OBJECTIVE

There is no consensus approach to covering skull base meningeal reflections-and cerebrospinal fluid (CSF) therein-of the posterior fossa cranial nerves (CNs VII-XII) when planning radiotherapy (RT) for medulloblastoma and ependymoma. We sought to determine whether MRI and specifically fast imaging employing steady-state acquisition (FIESTA) sequences can answer this anatomical question and guide RT planning.

METHODS

96 posterior fossa FIESTA sequences were reviewed. Following exclusions, measurements were made on the following scans for each foramen respectively (left, right); internal acoustic meatus (IAM) (86, 84), jugular foramen (JF) (83, 85) and hypoglossal canal (HC) (42, 45). A protocol describes measurement procedure. Two observers measured distances for five cases and agreement was assessed. One observer measured all the remaining cases.

RESULTS

IAM and JF measurement interobserver variability was compared. Mean measurement difference between observers was -0.275 mm (standard deviation 0.557). IAM and JF measurements were normally distributed. Mean IAM distance was 12.2 mm [95% confidence interval (CI) 8.8-15.6]; JF was 7.3 mm (95% CI 4.0-10.6). The HC was difficult to visualize on many images and data followed a bimodal distribution.

CONCLUSION

Dural reflections of posterior fossa CNs are well demonstrated by FIESTA MRI. Measuring CSF extension into these structures is feasible and robust; mean CSF extension into IAM and JF was measured. We plan further work to assess coverage of these structures with photon and proton RT plans. Advances in knowledge: We have described CSF extension beyond the internal table of the skull into the IAM, JF and HC. Oncologists planning RT for patients with medulloblastoma and ependymoma may use these data to guide contouring.

To be or not to be a neurovascular conflict: importance of the preoperative identification of the neurovascular conflict in the trigeminal neuralgia

The trigeminal neuralgia caused by neurovascular compression is a neurosurgical pathology requiring the preoperative identification as exact as possible of the neurovascular conflict. In this case, neuroimaging is very useful, as it allows not only the determination of the neurovascular conflict of the trigeminal nerve, but also the correct indication of an adequate surgical approach.

The incidence of double hypoglossal canal in Japanese: evaluation with multislice computed tomography

Background and Purpose

Double hypoglossal canal, namely a hypoglossal canal bridging, is a normal variation of the hypoglossal canal. Racial differences in the prevalence of double hypoglossal canal have been reported. We evaluated the prevalence of double hypoglossal canal in a Japanese population with multidetector computed tomography (MDCT).

Materials and Methods

We reviewed five hundred and ninety consecutive patients (mean age, 61 years: range, 15–94 years: 254 men, 336 women) who underwent computed tomographic angiography (CTA) of the brain for a variety of CNS abnormalities. Two radiologists achieved consensus on the canal being single or double, and measured the sizes of single canals on CT images. Kappa statistics was used to test the reliability between the 2 investigators. A logistic regression was used to evaluate the prevalence of double hypoglossal canal and the following factors: sex, age, and laterality. Student’s t-test was used to evaluate the asymmetry of single hypoglossal canal diameters. Statistical significance was accepted at P < 0.05.

Results

Double hypoglossal canal was identified in 16.9% of the patients, and was bilateral in 2.2%. Double hypoglossal canal was significantly more frequent on the left side than right (P = 0.004, odds ratio = 1.79) and in males than females (P = 0.011, odds ratio = 1.67). A larger left or right-sided canal was found in 31.6% and 12.2% of the patients, respectively, following the same side preference as that of double hypoglossal canal. Almost perfect agreement was achieved between the two readers (k = 0.975).

Conclusions

In this Japanese population, the prevalence of a double hypoglossal canal was 16.9%, of which 2.2% were bilateral. Double hypoglossal canal was more frequent in males than females, and on the left side than right.

Advances in magnetic resonance imaging of the skull base

Introduction Over the past 20 years, magnetic resonance imaging (MRI) has advanced due to new techniques involving increased magnetic field strength and developments in coils and pulse sequences. These advances allow increased opportunity to delineate the complex skull base anatomy and may guide the diagnosis and treatment of the myriad of pathologies that can affect the skull base. Objectives The objective of this article is to provide a brief background of the development of MRI and illustrate advances in skull base imaging, including techniques that allow improved conspicuity, characterization, and correlative physiologic assessment of skull base pathologies. Data Synthesis Specific radiographic illustrations of increased skull base conspicuity including the lower cranial nerves, vessels, foramina, cerebrospinal fluid (CSF) leaks, and effacement of endolymph are provided. In addition, MRIs demonstrating characterization of skull base lesions, such as recurrent cholesteatoma versus granulation tissue or abscess versus tumor, are also provided as well as correlative clinical findings in CSF flow studies in a patient pre- and post-suboccipital decompression for a Chiari I malformation. Conclusions This article illustrates MRI radiographic advances over the past 20 years, which have improved clinicians' ability to diagnose, define, and hopefully improve the treatment and outcomes of patients with underlying skull base pathologies.

Lesions of the skull base: imaging for diagnosis and treatment

This article provides a summary of how to approach the imaging analysis of lesions of the anterior, central, and posterior skull base. The primary focus is tumors and tumor-mimickers, and representative examples are shown to differentiate the features of lesions that can occur in the same location.

Intraoperative and anatomical descriptions of intracranial connections between the glossopharyngeal and vagus nerves: clinical implications

Object

Knowledge of the variations in the nerves of the posterior cranial fossa may be important during skull base approaches. To the authors' knowledge, intracranial neural interconnections between the glossopharyngeal and vagus nerves have not been previously investigated.

Methods

The senior author (A.C.G.) noted the presence of an intracranial interneural connection between the glossopharyngeal and vagus nerves during microvascular decompression surgery in a patient suffering from hemifacial spasm. To further investigate the approximate incidence and significance of such an interneural connection, the authors studied 40 adult human cadavers (80 sides) and prospectively evaluated 16 additional patients during microvascular procedures of the posterior cranial fossa.

Results

In the cadavers, the incidence of intracranial neural connections between the glossopharyngeal and vagus nerves was 2.5%. The only such connection found in our series of living patients was in the patient in whom the connection was initially identified. These interconnections were more common on the left side. Based on our findings, we classified these neural connections as Types I and II. In the cadavers, the length and width of this connection were approximately 9 mm and 1 mm, respectively. Histological analysis of these connections verified their neural content.

Conclusions

Although these connections are rare and the significance is unknown, knowledge of them may prove useful to surgeons who operate in the posterior fossa region so that they may avoid inadvertent traction or transection of these interconnections. Additionally, such connections might be considered in patients with recalcitrant neuralgia after microvascular decompression and rhizotomy of the glossopharyngeal nerve.

3D double-echo steady-state with water excitation MR imaging of the intraparotid facial nerve at 1.5T: a pilot study

BACKGROUND AND PURPOSE

The intraparotid facial nerve is difficult to delineate using conventional MR sequence. Our aim was to assess the value of 3D DESSWE MR imaging in depicting the normal anatomy of the intraparotid facial nerve.

MATERIALS AND METHODS

A 3D-DESSWE sequence was performed with optimum parameters in 18 healthy volunteers on a 1.5T MR imaging unit. The data obtained were reconstructed in relation to the course of the facial nerve by using the MPR and thin-section MIP programs. Images acquired were analyzed by 2 neuroradiologists. They made the initial evaluations independently but resolved inconsistencies by collaborative review and consensus agreement. The certainty of identifying the intraparotid facial nerve was scored and recorded on an arbitrary scale of 0-2. The lengths of the facial nerves were measured; CNRs of the facial nerves and parotid ducts were calculated. Statistical evaluation of the results was achieved by the 2-tailed Wilcoxon test, ANOVA, and a paired t test.

RESULTS

In all subjects, 3D DESSWE images provided a reliable definition of the normal facial nerve anatomy bilaterally. There were no significant differences between scores, lengths, and CNRs of bilateral facial nerves (P > .05). The intraparotid facial nerve, parotid ducts, and retromandibular vein showed high signal intensity while the surrounding soft tissue showed relatively low signal intensity. The signal intensity between the facial nerves and parotid ducts was significantly different (P < .01); but no differences could be obtained for the CNRs between the 2 structures (P > .05).

CONCLUSIONS

The 3D DESSWE sequence can display the intraparotid course of the normal facial nerve, including the relationship between the facial nerve and the parotid duct.

Detailed imaging of the normal anatomy and pathologic conditions of the cavernous region at 3 Tesla using a contrast-enhanced MR angiography

INTRODUCTION

The purpose of this study was to evaluate the potential of a high-resolution contrast-enhanced magnetic resonance angiography (CE-MRA) at 3 Tesla for the delineation of the cavernous sinus (CS) anatomy both under normal and under pathological conditions.

METHODS

Fifteen patients without pathologies in the CS and ten patients with pituitary adenomas were included. The CE-MRA was performed on a 3-Tesla scanner and analyzed collaboratively by two readers. The cranial nerves (CNs) within the CS, namely CNIII, CNIV, CNV1, CNV2, and CNVI, were identified in both patient groups. In the adenoma patients it was also assessed whether and to which extend the adenoma invaded the CS and the spatial relationship between tumor and CNs was determined.

RESULTS

In the patients with normal CS anatomy, CNIII could be identified in 100%, CNIV in 86.7%, and CNV1, CNV2, as well as CNVI in 100% of analyzed sides. Pituitary adenomas invaded the CS unilaterally (right side) in four patients, and bilaterally in six patients. In patients with adenomas, the CN could be identified and differentiated from the tumor in the following percentages: CNIII in 100%, CNIV in 70%, both CNV1 and CNV2 in 90%, and CNVI in 100%. In all these cases, the tumor-nerve spatial relationship could be visualized.

CONCLUSIONS

3-Tesla CE-MRA allows detailed imaging of the complex anatomy of the CS and its structures. In adenoma patients, it clearly visualizes the spatial relationship between tumor and CNs, and thus might be helpful to optimize presurgical planning.

Trigeminal neuralgia due to neurovascular compression: high-spatial-resolution diffusion-tensor imaging reveals microstructural neural changes

PURPOSE

To preoperatively detect, by using diffusion-tensor imaging coregistered with anatomic magnetic resonance (MR) imaging, suspected microstructural tissue changes of the trigeminal nerves in patients with trigeminal neuralgia (TN) resulting from neurovascular compression.

MATERIALS AND METHODS

The study was approved by the institutional review board, and written informed consent was obtained from all patients. Twenty patients (mean age, 51.3 years) with TN and evidence of neurovascular contact were examined with use of a 3.0-T MR unit combined with an eight-channel head coil before undergoing surgical decompression. A single-shot diffusion-tensor echo-planar sequence was used along 15 different diffusion directions, with a b value of 1000 sec/mm(2) and a section thickness of 2 mm. For anatomic correlation, 0.6-mm isotropic three-dimensional fast imaging employing steady-state images were acquired for coregistration with the functional diffusion-tensor maps. After region of interest placement, mean fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values were calculated for each nerve by using the paired-sample two-tailed t test (with P < .005 indicating significance) and compared with surgical findings.

RESULTS

FA was significantly lower (P = .004) on the trigeminal neuralgia-affected side (mean FA, 0.203) than on the contralateral side (mean FA, 0.239). ADCs were nearly identical between the normal and TN-affected nerve tissues.

CONCLUSION

These findings suggest that diffusion-tensor imaging enables the identification and quantification of anisotropic changes between normal nerve tissue and TN-affected trigeminal nerves. Coregistration of anatomic three-dimensional fast imaging employing steady-state imaging and diffusion-tensor imaging facilitates excellent delineation of the cisternal segments of the trigeminal nerves.

Imaging study of the long extracranial extension of the inferior petrosal sinus with MSCT

The aim of this study was to explore the anatomic route of Long-Inferior Petrosal Sinuses (IPS) with multi-slice spiral computed tomography, and to provide referenced evidence for the interventional preoperative evaluation for the diagnosis and treatment of skull base and sellar lesions. The route of Long-IPS and its confluence with the internal jugular vein (IJV) and the connection level of 12 IPS were shown with multi-planar reconstruction and curved multi-planar reconstruction, and the IPS length was determined. Combining the results of continuous multi-slice scanning, the diameters of the IPS at the initial segment in the jugular foreman and middle segment and the confluence segment of the IPS-IJV junction level were determined. The mean length of the Long-IPS was 66.2 +/- 17.5 mm, and the length was over 60 mm on eight sides and its peak value 100 mm. The mean diameters of the IPS were 2.4 mm +/- 0.7 mm, 2.1 mm +/- 0.4 mm, and 2.1 mm +/- 0.5 mm at the initial, middle, and confluent segments, respectively. Their diameters were equal to or greater than 2 mm at the connection level on eight sides. Furthermore, the diameter was greater than 1.6 mm at the middle and initial segments. The Long-IPS might be used as a route to the intra-cranial IPS. MSCT is helpful for showing the route and variation of the IPS and could be an effective method for preoperative evaluation of the IPS.

[Anatomy of the skull base and the cranial nerves in slice imaging]

Computed tomography (CT) and magnetic resonance imaging (MRI) are suitable methods for examination of the skull base. Whereas CT is used to evaluate mainly bone destruction e.g. for planning surgical therapy, MRI is used to show pathologies in the soft tissue and bone invasion. High resolution and thin slice thickness are indispensible for both modalities of skull base imaging. Detailed anatomical knowledge is necessary even for correct planning of the examination procedures. This knowledge is a requirement to be able to recognize and interpret pathologies. MRI is the method of choice for examining the cranial nerves. The total path of a cranial nerve can be visualized by choosing different sequences taking into account the tissue surrounding this cranial nerve. This article summarizes examination methods of the skull base in CT and MRI, gives a detailed description of the anatomy and illustrates it with image examples.

Detailed MR imaging anatomy of the cisternal segments of the glossopharyngeal, vagus, and spinal accessory nerves in the posterior fossa: the use of 3D balanced fast-field echo MR imaging

BACKGROUND AND PURPOSE

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.

MATERIALS AND METHODS

3D-bFFE was used to image the cisternal segments of the lower CNs in 20 healthy volunteers. As an anatomic landmark, CSF recesses adjacent to the JF were divided into 3 parts: the recess for the cochlear aqueduct, the recess for CN IX, and the recess for the CN X/XI complex. MR images were evaluated to identify the cisternal segment of each cranial nerve in relation to these anatomic landmarks.

RESULTS

The mean angles of the recess for the cochlear aqueduct for CN IX and CN X/XI to the posterior petrous bone were 41.6 +/- 2.5 degrees , 69.7 +/- 3.1 degrees , and 76.0 +/- 3.4 degrees , respectively (P < .01). The mean length of the recess for the cochlear aqueduct for CN IX and the CN X/XI complex was 5.91 +/- 0.19, 5.08 +/- 0.11, and 4.76 +/- 0.13 cm, respectively (P < .01). 3D-bFFE adequately depicted the cisternal segments of CN IX on 38 sides (95%) and the CN X/XI complex on 39 sides (97.5%).

CONCLUSIONS

The cisternal segments of CN IX, CN X, and CN XI are well identified by using 3D-bFFE, especially by determining the angles of the CSF recesses adjacent to the JF.