Imaging of the glossopharyngeal, vagus, and accessory nerves

On the Cranial Nerves

The twelve cranial nerves play a crucial role in the nervous system, orchestrating a myriad of functions vital for our everyday life. These nerves are each specialized for particular tasks. Cranial nerve I, known as the olfactory nerve, is responsible for our sense of smell, allowing us to perceive and distinguish various scents. Cranial nerve II, or the optic nerve, is dedicated to vision, transmitting visual information from the eyes to the brain. Eye movements are governed by cranial nerves III, IV, and VI, ensuring our ability to track objects and focus. Cranial nerve V controls facial sensations and jaw movements, while cranial nerve VII, the facial nerve, facilitates facial expressions and taste perception. Cranial nerve VIII, or the vestibulocochlear nerve, plays a critical role in hearing and balance. Cranial nerve IX, the glossopharyngeal nerve, affects throat sensations and taste perception. Cranial nerve X, the vagus nerve, is a far-reaching nerve, influencing numerous internal organs, such as the heart, lungs, and digestive system. Cranial nerve XI, the accessory nerve, is responsible for neck muscle control, contributing to head movements. Finally, cranial nerve XII, the hypoglossal nerve, manages tongue movements, essential for speaking, swallowing, and breathing. Understanding these cranial nerves is fundamental in comprehending the intricate workings of our nervous system and the functions that sustain our daily lives.

Guidelines for radiographic imaging of cranial neuropathies

Disruption of the complex pathways of the 12 cranial nerves can occur at any site along their course, and many, varied pathologic processes may initially manifest as dysfunction and neuropathy. Radiographic imaging (computed topography or magnetic resonance imaging) is frequently used to evaluate cranial neuropathies; however, indications for imaging and imaging method of choice vary considerably between the cranial nerves. The purpose of this review is to provide an analysis of the diagnostic yield and the most clinically appropriate means to evaluate cranial neuropathies using radiographic imaging. Using the PubMed MEDLINE NCBI database, a total of 49,079 articles' results were retrieved on September 20, 2014. Scholarly articles that discuss the etiology, incidence, and use of imaging in the context of evaluation and diagnostic yield of the 12 cranial nerves were evaluated for the purposes of this review. We combined primary research, guidelines, and best practice recommendations to create a practical framework for the radiographic evaluation of cranial neuropathies.

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.

End-organ radiographic manifestations of cranial neuropathies: A concise review

BACKGROUND

Cranial neuropathies are a spectrum of disorders associated with dysfunction of one or more of the twelve cranial nerves and the subsequent anatomic structures they innervate.

OBJECTIVE

The purpose of this article is to review radiographic imaging findings of end-organ aberrations secondary to cranial neuropathies.

METHOD

All articles related to cranial neuropathies were retrieved through the PubMed MEDLINE NCBI database from January 1, 1991 to August 31, 2014. These manuscripts were analyzed for their relation to cranial nerve end-organ disease pathogenesis and radiographic imaging.

RESULTS

The present review reveals detectable end-organ changes on CT and/or MRI for the following cranial nerves: olfactory nerve, optic nerve, oculomotor nerve, trochlear nerve, trigeminal nerve, abducens nerve, facial nerve, vestibulocochlear nerve, glossopharyngeal nerve, vagus nerve, accessory nerve, and hypoglossal nerve.

CONCLUSION

Radiographic imaging can assist in the detailed evaluation of end-organ involvement, often revealing a corresponding cranial nerve injury with high sensitivity and diagnostic accuracy. A thorough understanding of the distal manifestations of cranial nerve disease can optimize early pathologic detection as well as dictate further clinical management.

Human vagus nerve branching in the cervical region

BACKGROUND

Vagus nerve stimulation is increasingly applied to treat epilepsy, psychiatric conditions and potentially chronic heart failure. After implanting vagus nerve electrodes to the cervical vagus nerve, side effects such as voice alterations and dyspnea or missing therapeutic effects are observed at different frequencies. Cervical vagus nerve branching might partly be responsible for these effects. However, vagus nerve branching has not yet been described in the context of vagus nerve stimulation.

MATERIALS AND METHODS

Branching of the cervical vagus nerve was investigated macroscopically in 35 body donors (66 cervical sides) in the carotid sheath. After X-ray imaging for determining the vertebral levels of cervical vagus nerve branching, samples were removed to confirm histologically the nerve and to calculate cervical vagus nerve diameters and cross-sections.

RESULTS

Cervical vagus nerve branching was observed in 29% of all cases (26% unilaterally, 3% bilaterally) and proven histologically in all cases. Right-sided branching (22%) was more common than left-sided branching (12%) and occurred on the level of the fourth and fifth vertebra on the left and on the level of the second to fifth vertebra on the right side. Vagus nerves without branching were significantly larger than vagus nerves with branches, concerning their diameters (4.79 mm vs. 3.78 mm) and cross-sections (7.24 mm2 vs. 5.28 mm2).

DISCUSSION

Cervical vagus nerve branching is considerably more frequent than described previously. The side-dependent differences of vagus nerve branching may be linked to the asymmetric effects of the vagus nerve. Cervical vagus nerve branching should be taken into account when identifying main trunk of the vagus nerve for implanting electrodes to minimize potential side effects or lacking therapeutic benefits of vagus nerve stimulation.

Uncommon and rare causes of vocal fold paralysis detected via imaging

BACKGROUND

Cross-sectional imaging can be used to trace the course of the vagus nerve and its laryngeal branches to detect many of the causes of vocal fold paralysis. The most frequent aetiologies are surgical injury and tumoural involvement of the recurrent laryngeal nerve anywhere along its course.

METHOD

This review article focuses on the uncommon and rare causes of vocal fold paralysis that have been detected or diagnosed on cross-sectional imaging.

RESULTS AND CONCLUSION

Uncommon causes included a tortuous oesophagus, tracheal diverticulum, cervical osteophytes and cardiovocal syndrome. These examples are presented with clinical case histories and radiological appearances, and are discussed in the context of the current literature.

Magnetic resonance cisternographic evaluation of glossopharyngeal, vagus, and accessory nerves

PURPOSE

The individual visualization of the glossopharyngeal, vagus, and accessory nerves has been a troublesome issue. After the recent developments in the microsurgical field, the detailed knowledge of the relationship of these nerves and the tumour has gained importance. The purpose of this study is to compare the visibility of each of these nerves.

METHODS

Thirty patients (M/F: 14/16; mean age 52.46 years) with complaints of vertigo, tinnitus, and hearing loss were examined with routine temporal magnetic resonance imaging (MRI) study. The imaging protocol consisted of 3-dimensional fast imaging with steady state acquisition in axial and sagittal oblique planes in addition to routine sequences. These images were transferred to a workstation and reformatted. Visibility of the nerves was evaluated by consensus of 2 radiologists who used an evaluation scale of 2 (excellently visible), 1 (partially visible), to 0 (not visible).

RESULTS

In 26 patients, both sides were scanned; in 4 patients, only one side was scanned. A total of 168 nerves were investigated. The rates for visualization for each nerve were as follows: glossopharyngeal nerve, 100% and 100%; vagus nerve, 67.9% and 100%; and accessory nerve, 10.8% and 83.85% on axial and sagittal oblique 3-dimensional fast imaging with steady state acquisition, respectively.

CONCLUSIONS

Glossopharyngeal, vagus, and accessory nerve assessment improved when images were obtained in the sagittal oblique plane to the jugular foramen.

Imaging the cranial nerves: Part I: methodology, infectious and inflammatory, traumatic and congenital lesions

Many disease processes manifest either primarily or secondarily by cranial nerve deficits. Neurologists, ENT surgeons, ophthalmologists and maxillo-facial surgeons are often confronted with patients with symptoms and signs of cranial nerve dysfunction. Seeking the cause of this dysfunction is a common indication for imaging. In recent decades we have witnessed an unprecedented improvement in imaging techniques, allowing direct visualization of increasingly small anatomic structures. The emergence of volumetric CT scanners, higher field MR scanners in clinical practice and higher resolution MR sequences has made a tremendous contribution to the development of cranial nerve imaging. The use of surface coils and parallel imaging allows sub-millimetric visualization of nerve branches and volumetric 3D imaging. Both with CT and MR, multiplanar and curved reconstructions can follow the entire course of a cranial nerve or branch, improving tremendously our diagnostic yield of neural pathology. This review article will focus on the contribution of current imaging techniques in the depiction of normal anatomy and on infectious and inflammatory, traumatic and congenital pathology affecting the cranial nerves. A detailed discussion of individual cranial nerves lesions is beyond the scope of this article.

Imaging the cranial nerves: part II: primary and secondary neoplastic conditions and neurovascular conflicts

There have been unprecedented improvements in cross-sectional imaging in the last decades. The emergence of volumetric CT, higher field MR scanners and higher resolution MR sequences is largely responsible for the increasing diagnostic yield of imaging in patients presenting with cranial nerve deficits. The introduction of parallel MR imaging in combination with small surface coils allows the depiction of submillimetric nerves and nerve branches, and volumetric CT and MR imaging is able to provide high quality multiplanar and curved reconstructions that can follow the often complex course of cranial nerves. Seeking the cause of a cranial nerve deficit is a common indication for imaging, and it is not uncommon that radiologists are the first specialists to see a patient with a cranial neuropathy. To increase the diagnostic yield of imaging, high-resolution studies with smaller fields of view are required. To keep imaging studies within a reasonable time frame, it is mandatory to tailor the study according to neuro-topographic testing. This review article focuses on the contribution of current imaging techniques in the depiction of primary and secondary neoplastic conditions affecting the cranial nerves as well as on neurovascular conflicts, an increasingly recognized cause of cranial neuralgias.

Imaging of muscular denervation secondary to motor cranial nerve dysfunction

The effects of motor cranial nerve dysfunction on the computed tomography (CT) and magnetic resonance imaging (MRI) appearances of head and neck muscles are reviewed. Patterns of denervation changes are described and illustrated for V, VII, X, XI and XII cranial nerves. Recognition of the range of imaging manifestations, including the temporal changes in muscular appearances and associated muscular grafting or compensatory hypertrophy, will avoid misinterpretation as local disease. It will also prompt the radiologist to search for underlying cranial nerve pathology, which may be clinically occult. The relevant cranial nerve motor division anatomy will be described to enable a focussed search for such a structural abnormality.

[Visualization of the lower cranial nerves by 3D-FIESTA]

MR cisternography has been introduced for use in neuroradiology. This method is capable of visualizing tiny structures such as blood vessels and cranial nerves in the cerebrospinal fluid (CSF) space because of its superior contrast resolution. The cranial nerves and small vessels are shown as structures of low intensity surrounded by marked hyperintensity of the CSF. In the present study, we evaluated visualization of the lower cranial nerves (glossopharyngeal, vagus, and accessory) by the three-dimensional fast imaging employing steady-state acquisition (3D-FIESTA) sequence and multiplanar reformation (MPR) technique. The subjects were 8 men and 3 women, ranging in age from 21 to 76 years (average, 54 years). We examined the visualization of a total of 66 nerves in 11 subjects by 3D-FIESTA. The results were classified into four categories ranging from good visualization to non-visualization. In all cases, all glossopharyngeal and vagus nerves were identified to some extent, while accessory nerves were visualized either partially or entirely in only 16 cases. The total visualization rate was about 91%. In conclusion, 3D-FIESTA may be a useful method for visualization of the lower cranial nerves.