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.     

MR neurography: past, present, and future

OBJECTIVE: MR neurography (MRN) has increasingly been used in clinical practice for the evaluation of peripheral nerve disease. This article reviews the historic perspective of MRN, the current imaging trends of this modality, and the future directions and applications that have shown potential for improved imaging and diagnostic capabilities. CONCLUSION: MRN has come a long way in the past 2 decades. Excellent depiction of 3D nerve anatomy and pathology is currently possible. Further technical developments in diffusion-based nerve and muscle imaging, whole-body MRN, and nerve-specific MR contrast agents will likely play a major role in advancing this novel field and understanding peripheral neuromuscular diseases in the years to come.     

CT and MR imaging of the normal and pathologic conditions of the facial nerve.

Computed tomography (CT) and magnetic resonance imaging (MRI) are well established imaging modalities to examine the facial nerve as well as the course of the facial nerve itself. High spatial resolution is guaranteed not only in the x- and y-axis, but also in the z-axis using multislice spiral CT. With this technique, reformatted multiplanar images in oblique planes, avoiding additional examinations in the coronal plane, facilitate the delineation of the facial nerve canal. This is beneficial in patients with temporal bone trauma, malformation or osseous changes. MR has a superior soft-tissue contrast to CT that enables imaging of the facial nerve itself. Therefore the normal facial nerve as well as pathologic changes of the facial nerve is readily visualized from the brain stem to the parotid gland. This review article presents anatomy, pathology and imaging strategies in the diagnostics of the facial nerve.     

Coronal MR imaging of the normal 3rd, 4th, and 5th lumbar and 1st sacral nerve roots

Seven healthy volunteers underwent coronal MR imaging at 1.5 tesla of the normal 3rd, 4th, and 5th lumbar, and 1st sacral nerve roots. Coronal slices, 3-mm-thick with a 0.3-mm gap between the slices were obtained (TR/TE 600/22) through the lumbar spinal canal. All the nerve roots were visible on at least one image. One can routinely expect to demonstrate the 3rd, 4th, and 5th lumbar, and 1st sacral nerve roots on T1-weighted, 3-mm-thick coronal MR scans. We found no correlation between the degree of lumbar lordosis and the lengths of the visible nerve roots. Five patients with one of the following spinal problems: anomaly, tumor, disk herniation, and failed back surgery syndrome were examined according to our protocol. In all these cases coronal MR imaging gave the correct diagnosis.     

正常成人L_4及L_5神经根斜冠状位T_1W MR表现

目的:探讨正常成人L4及L5神经根斜冠状位T1W MR成像在脊神经根显示方面的价值。方法:41例正常成人在常规腰骶部MR扫描基础上,沿轴位图像右侧或左侧、L3～L4或L4～L5椎间孔方向、分别行双侧相应神经根斜冠状位T1W MR成像。统计根管内段神经根清晰、不清晰及变异神经根个数。结果:40例共160个脊神经根T1W斜冠状位图像均能清晰、连续显示其根管内段走行,其中1例可见右侧L4和L5神经根共干;1例志愿者斜冠状位图像神经根显示欠清晰。结论:L4及L5神经根斜冠状位T1W MR成像,对神经根在根管内段走行显示清晰,能为临床诊断及治疗提供较大帮助。     

Magnetic resonance imaging of the elbow. Part II: Abnormalities of the ligaments, tendons, and nerves

Part II of this comprehensive review on magnetic resonance imaging of the elbow discusses the role of magnetic resonance imaging in evaluating patients with abnormalities of the ligaments, tendons, and nerves of the elbow. Magnetic resonance imaging can yield high-quality multiplanar images which are useful in evaluating the soft tissue structures of the elbow. Magnetic resonance imaging can detect tears of the ulnar collateral ligament and lateral collateral ligament of the elbow with high sensitivity and specificity. Magnetic resonance imaging can determine the extent of tendon pathology in patients with medial epicondylitis and lateral epicondylitis. Magnetic resonance imaging can detect tears of the biceps tendon and triceps tendon and can distinguishing between partial and complete tendon rupture. Magnetic resonance imaging is also helpful in evaluating patients with nerve disorders at the elbow.Part I of this review can be found at:     

Ultrasound and magnetic resonance imaging of the peripheral nerves: current techniques, promising directions, and open issues

High-resolution ultrasound (US) and magnetic resonance (MR) imaging are the two imaging methods of choice for the study of peripheral nerves. The many advances that have been made in recent years, either by US or MR imaging, including diffusion tensor imaging and tractography, offer new perspectives for the assessment of many pathological processes affecting peripheral nerves such as entrapment syndromes, tumors and tumor-like lesions, and traumatic disorders. Most of these improvements have especially increased the spatial resolution of nerve imaging. US and MR imaging are complementary, each having advantages and disadvantages. Tractography is still emerging in the musculoskeletal field, particularly for the analysis of peripheral nerves, but this technique seems promising.     

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.     

Pathology of the vestibulocochlear nerve

There is a large scala of pathology affecting the vestibulocochlear nerve. Magnetic resonance imaging is the method of choice for the investigation of pathology of the vestibulocochlear nerve. Congenital pathology mainly consists of agenesis or hypoplasia of the vestibulocochlear nerve. Tumoral pathology affecting the vestibulocochlear nerve is most frequently located in the internal auditory canal or cerebellopontine angle. Schwannoma of the vestibulocochlear nerve is the most frequently found tumoral lesion followed by meningeoma, arachnoid cyst and epidermoid cyst. The most frequently encountered pathologies as well as some more rare entities are discussed in this chapter.     

Magnetic resonance imaging in paralysis of the upper limb of traumatic origin

We have used magnetic resonance imaging in addition to the other imaging techniques for the examination of 31 patients with traumatic upper limb paralysis. The therapeutic indications of traumatic brachial plexus paralysis depend on the early and precise assessment of the lesions. Computed tomography with a contrast injection at a lumbar level opacifying the subarachnoid spaces provides a morphological study of the canal, spine and nerve roots and of container-contents relationships. In our experience, the diagnostic reliability for the detection of intraspinal radicular lesions is 86%. A study in all 3 spatial planes is possible with MRI with T1- and T2-weighted or gradient echo sequences. The reliability of the technique for the diagnosis of meningoceles in the detection of nerve root avulsion is similar to that of CT (85%). The excellent spatial resolution and natural high contrast allow following the nerve roots in their extraspinal course and determining the site of nerve trunk rupture (50%). The use of oblique and double-obliquity sections should yet improve these results. These first results lead us to proposing magnetic resonance imaging for the exploration of traumatic lesions of the brachial plexus. This nonagressive, more precise and more complete assessment of the lesions certainly has a significant influence on therapeutic choice.     

Imaging of denervation in the head and neck

Denervation changes maybe the first sign of a cranial nerve injury. Recognition of denervation patterns can be used to determine the site and extent of a lesion and to tailor imaging studies according to the most likely location of an insult along the course of the affected cranial nerve(s). In addition, the extent of denervation can be used to predict functional recovery after treatment. On imaging, signs of denervation can be misleading as they often mimic recurrent neoplasm or inflammatory conditions. Imaging can both depict denervation related changes and establish its cause.This article briefly reviews the anatomy of the extracranial course of motor cranial nerves with particular emphasis on the muscles supplied by each nerve, the imaging features of the various stages of denervation, the different patterns of denervation that maybe helpful in the topographic diagnosis of nerve lesions and the most common causes of cranial nerve injuries leading to denervation.     

腰骶部脊神经MRI成像技术的应用进展

MRI具有良好的组织对比分辨力,能清晰的显示腰骶部脊神经根及其周围的软组织,成为评估脊神经根病变的理想手段。随着MRI技术的发展,越来越多的新的成像技术应用于临床,包括磁共振神经成像术、选择性水激励脂肪抑制技术、平衡式稳态自由进动序列、扩散张量成像等对神经根病变的诊断、术前评估等方面起着越来越重要的作用。本文综述了MRI成像技术在腰骶部脊神经根中的应用进展。     

MR imaging of the intraparotid facial nerve: normal anatomy and pathology

Three normal volunteers, 58 normal patients, and three patients with parotid tumors were studied with a 0.3 T permanent-magnet imaging system to directly image the intraparotid facial nerve. On T1-weighted images the nerve appeared as a curvilinear structure of relatively low signal intensity within the fatty, high-signal parotid parenchyma. Its major divisions and branches could be imaged only with specially angled axial scan planes. To verify our observations MR imaging was compared with whole-organ cryomicrotome sections cut at the same angles. Normal variations in the appearance of the nerve and pitfalls in its visualization are discussed. Three cases of parotid tumors, with surgical confirmation of the relationship of the facial nerve to the tumor, are presented. MR is the only imaging technique capable of direct imaging of the facial nerve in the parotid bed: it may assist materially in the surgical management of tumors of the parotid gland.     

Sarcoidosis of the eye, orbit, and central nervous system. Role of MR imaging

Sarcoidosis, a systemic disease of unknown cause, frequently involves the eye, orbit, and central nervous system. The MR imaging findings of orbital and optic pathway sarcoidosis may closely resemble several other orbital and intracranial diseases. This article reviews MR imaging findings of sarcoidosis when it involves the eye, orbit, and visual pathways. Careful review of MR findings and other neuroimaging findings and clinical characteristics will reduce the incidence of mistaking optic nerve and chiasmal sarcoidosis for meningioma or glioma.     

Sonography, CT, CT sialography, MRI and MRI sialography in investigation of the facial nerve and the differentiation between deep and superficial parotid lesions

Our aim was to explore the possibility of delineation of the facial nerve within the parotid gland and to differentiate between superficial and deep parotid lesions in relationship to it, using ultrasound, CT, MRI, MRI sialography (MRIS) and CT sialography (CTS). We examined 47 patients with clinically suspected parotid tumours by US, 31 of them also by CT, MRI and CTS, and 13 by MRIS as well. Low-intensity curvilinear structures seen on T1-weighted MRI were delineated better after intraductal gadolinium injection and proved to represent parotid ducts on CTS. Using the main parotid duct as a landmark, we distinguished parotid lesions as deep or superficial to the facial nerve by T1-weighted MRI images in 69 % and by MRIS in all cases. The facial nerve itself was indistinguishable from the parotid gland in all our imaging methods. Received: 25 March 1996 Accepted: 30 August 1996     

Clinical-radiologic issues in perineural tumor spread of malignant diseases of the extracranial head and neck.

The radiologic and clinical records of 52 patients with radiologically documented perineural tumor were reviewed to assess the spectrum of tumors responsible, the nerves most commonly involved, and the optimal methods for imaging perineural tumor infiltration. Perineural tumor infiltration was most commonly seen with head and neck squamous cell carcinoma, followed by adenoid cystic carcinoma and several others, such as non-Hodgkin lymphoma, malignant schwannoma, minor salivary gland malignancy, and other sarcomas. The second and third divisions of the trigeminal nerve and the facial nerve were most commonly involved with perineural tumor. Both antegrade and retrograde perineural tumor spread were seen, although retrograde spread was significantly more common. Both high-resolution direct coronal computed tomography and magnetic resonance (MR) imaging clearly showed perineural tumor below the skull base. MR imaging best depicted skull base, cisternal, and brain stem perineural tumor infiltration. T1-weighted MR imaging before and after administration of gadopentetate dimeglumine is the study of choice in investigation of perineural tumor.     

High-resolution MR neurography of diffuse peripheral nerve lesions

High-resolution MR imaging of peripheral nerves is becoming more common and practical with the increasing availability of 3T magnets. There are multiple reports of MR imaging of peripheral nerves in compression and entrapment neuropathies. However, there is a relative paucity of literature on MRN appearance of diffuse peripheral nerve lesions. We attempted to highlight the salient imaging features of myriad diffuse peripheral nerve disorders and imaging techniques for MRN. Using clinical and pathologically proved relevant examples, we present the MRN appearance of various types of diffuse peripheral nerve lesions, such as traumatic, inflammatory, infectious, hereditary, radiation-induced, neoplastic, and tumor variants.     

MR imaging in the differential diagnosis of neurogenic foot drop

BACKGROUND AND PURPOSE: Prolonged T2 relaxation time of denervated muscle has been described in several clinical and experimental studies. The purpose of this study was to evaluate the utility of MR imaging in the diagnosis of neurogenic muscle disorders compared with that of clinical and electrophysiologic examination. METHODS: In a prospective study, 40 consecutive patients clinically presenting with a foot drop were included. MR imaging of the lower leg included axial T1-weighted and axial turbo inversion recovery magnitude (TIRM) sequences. Two readers blinded to clinical data evaluated T1-weighted images for anatomic localization of affected muscles and TIRM images for patterns of signal intensity increase. After MR imaging, a detailed neurophysiologic examination was performed. Cause of foot drop was independently determined on the basis of MR and electrophysiologic data. RESULTS: Clinical examination and electromyography (EMG) disclosed 20 peroneal nerve lesions, nine cases of L5 radiculopathy, and 11 nerve lesions extending beyond neural structures. MR imaging revealed three distinct patterns of signal intensity increase on TIRM images: peroneal nerve pattern, L5 pattern, and unspecific pattern. MR imaging and EMG findings were in agreement in 37 (92%) of 40 patients. In three patients, MR imaging revealed a more widespread involvement than did EMG. In one of these patients, denervation in the corresponding muscle was validated by follow-up EMG. No false-negative diagnoses were made by use of MR imaging as compared with use of EMG. CONCLUSION: MR imaging improves accuracy in the differential diagnosis of peripheral nerve lesions compared with that of EMG and can supplement EMG in the diagnosis of denervated muscles.     

MRI脂肪抑制和增强技术在诊断眼眶疾病中的应用

目的 研究磁共振脂肪抑制技术和钆喷替酸菊甲胺（Ｇｄ－ＤＴＰＡ）增强造影在眼眶病变中的应用及其价值。方法 对８５例眼球和眶内病变分别行平扫、使用脂肪抑制技术和（或）Ｇｄ－ＤＴＰＡ增强扫描,并比较分析使用脂肪抑制技术前后以及增强扫描对病变的显示情况。结果 ８５例眼球和眶内病变的边缘、轮廓和范围及其周围正常结构的关系在使用脂肪抑制技术后的扫描序列上较在未使用该技术的序列上显示得准确清楚。７例视神经不增粗     

Perineural spread of malignant melanoma of the head and neck: clinical and imaging features

BACKGROUND AND PURPOSE: Extension of malignant melanoma along cranial nerves is a little-known complication of malignant melanoma of the head and neck. We describe the clinical and MR imaging findings of perineural spread of malignant melanoma to cranial nerves, emphasizing that this entity occurs more commonly with desmoplastic histology and may have a long latent period following primary diagnosis. METHODS: At two institutions, we identified and retrospectively reviewed eight cases of malignant melanoma of the head and neck that had MR imaging evidence of perineural spread of disease. All patients underwent confirmatory tissue sampling. RESULTS: Seven patients had melanomas of the facial skin or lip, and one patient had a primary sinonasal lesion. By histopathology, these melanomas included five desmoplastic, two mucosal, and one poorly differentiated melanotic spindle-cell tumor. All patients developed symptomatic cranial neuropathy an average of 4.9 years from the time of initial diagnosis. MR imaging demonstrated postgadolinium enhancement of at least one branch of the trigeminal nerve in all cases and of at least one other cranial nerve in five cases. Other findings included abnormal contrast enhancement and soft tissue thickening in the cavernous sinus, Meckel's cave, and/or the cisternal segment of the trigeminal nerve. CONCLUSION: Although perineural spread of disease occurs most commonly with squamous cell carcinoma and adenoid cystic carcinoma, malignant melanoma must also be included in this differential diagnosis, particularly if the patient's pathology is known to be desmoplastic. Similarly, any patient with malignant melanoma of the head and neck who undergoes MR imaging should receive an imaging assessment focused on the likely routes of perineural spread.