Vagal neuropathy: evaluation with CT and MR imaging

The ptotic tongue-imaging appearance and pathology localization along the course of the hypoglossal nerve

CT and MRI findings of tongue ptosis and atrophy should alert radiologists to potential pathology along the course of the hypoglossal nerve (cranial nerve XII), a purely motor cranial nerve which supplies the intrinsic and extrinsic muscles of the tongue. While relatively specific for hypoglossal nerve pathology, these findings do not accurately localize the site or cause of denervation. A detailed understanding of the anatomic extent of the nerve, which crosses multiple anatomic spaces, is essential to identify possible underlying pathology, which ranges from benign postoperative changes to life-threatening medical emergencies. This review will describe key imaging findings of tongue denervation, segmental anatomy of the hypoglossal nerve, imaging optimization, and comprehensive imaging examples of diverse pathology which may affect the hypoglossal nerve. Armed with this knowledge, radiologists will increase their sensitivity for detection of pathology and provide clinically relevant differential diagnoses when faced with findings of tongue ptosis and denervation.

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.

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.

Causes and imaging manifestations of paralysis of the recurrent laryngeal nerve

The vocal cords play a key role in the functions of the larynx. Their motor innervation depends on the recurrent laryngeal nerve (a branch of the tenth cranial nerve), which follows a long trajectory comprising intracranial, cervical, and mediastinal segments. Vocal cord paralysis usually manifests as dysphonia, the main symptom calling for CT study, the first-line imaging test to investigate the cause of the lesion. Patients are asymptomatic in a third of cases, so the incidental detection of signs of vocal cord paralysis in a CT study done for other reasons should prompt a search for a potentially severe occult lesion. This article aims to familiarize readers with the anatomy of the motor innervation of the glottis, the radiological presentation and most common causes of vocal cord paralysis, and conditions that can simulate vocal cord paralysis.

Prevalence of vocal cord paralysis in patients with incidentally discovered enlarged lymph nodes along the expected course of the recurrent laryngeal nerve

OBJECTIVES

We sought to determine the prevalence of vocal cord paralysis in patients with incidentally discovered lymphadenopathy along the expected course of the recurrent laryngeal nerve (RLN).

METHODS

We reviewed the positron-emission tomographic (PET) and computed tomographic (CT) scans of 936 consecutive patients with a variety of diagnoses. Enlarged lymph nodes (short-axis diameter of more than 1 cm) along the expected course of the RLN were identified. Patients with lymphadenopathy were evaluated for CT signs of vocal cord paralysis. The medical records of patients with lymphadenopathy were reviewed for clinical signs of vocal cord paralysis. Patients with head and neck malignancies were excluded from the study.

RESULTS

Lymphadenopathy along the course of the RLN was identified in 57 of the 936 patients studied. Fifty-three of the 57 patients (93%) were found to have a malignancy. Thirty-four enlarged nodes (60%) had FDG uptake as shown on a PET/CT scan. Twenty enlarged nodes (35%) had CT evidence of extracapsular spread. Four patients (7%) had CT evidence of vocal cord paralysis. One patient (2%) had clinical evidence of vocal cord paralysis.

CONCLUSIONS

In asymptomatic patients with incidental lymphadenopathy along the course of the RLN, vocal cord paralysis is rare.

Losing your voice: etiologies and imaging features of vocal fold paralysis

Neurogenic compromise of vocal fold function exists along a continuum encompassing vocal cord hypomobility (paresis) to vocal fold immobility (paralysis) with varying degrees and patterns of reinnervation. Vocal fold paralysis (VFP) may result from injury to the vagus or the recurrent laryngeal nerves anywhere along their course from the brainstem to the larynx. In this article, we review the anatomy of the vagus and recurrent laryngeal nerves and examine the various etiologies of VFP. Selected cases are presented with discussion of key imaging features of VFP including radiologic findings specific to central vagal neuropathy and peripheral recurrent nerve paralysis.

Diagnostic Testing for Vocal Fold Paralysis: Survey of Practice and Evidence-Based Medicine Review

OBJECTIVES/HYPOTHESIS

Vocal fold paralysis continues to be a dominant topic in laryngology. Although the majority of cases can be attributed to a known etiology, a significant number of patients present without a clear precipitating event. Over 1,500 studies regarding vocal fold paralysis exist in the medical literature, although only a small percentage report on the use of serum or radiographic testing for the evaluation of idiopathic paralysis. Despite this, patients are routinely subjected to diagnostic evaluation to investigate the underlying cause. To characterize contemporary practice, a national survey of the American Broncho-Esophagological Association (ABEA) membership was undertaken. It is hypothesized that the current practice of diagnostic testing for idiopathic vocal fold paralysis is not well supported by an evidence-based medicine (EBM) review of the available medical literature.

STUDY DESIGN

The authors conducted a national survey, systematic EBM review of existing literature.

METHODS

Surveys were mailed to all active ABEA members; responses regarding practice specialization as well as serum/radiographic diagnostic preferences for idiopathic vocal fold paralysis were tabulated and subjected to statistical analysis. To compare contemporary practice with evidence in the available literature, an EBM review was first performed. Articles for evaluation were selected from a Medline search of English-language abstracts related to adult vocal fold paralysis. The publications were individually reviewed and an EBM level and grade were assigned and compared with the survey results.

RESULTS

Eighty-four of 249 active members responded with 76 (31%) replies submitted for analysis. Specific serum tests were advocated by 41 of 76 (54%) respondents, although the majority (52 of 65 [80%]) felt that they were only "occasionally" or "never" necessary. The most common tests were rheumatoid factor (38%), Lyme titer (36%), erythrocyte sedimentation rate (34%), and antinuclear antibody (33%). Fifty-one of 71(72%) felt that computed tomography (CT) was "always" or "often" necessary and 50 of 72 (69%) replied that chest radiography (CXR) was "always" or "often" necessary. There was no significant difference between CT and CXR ordering (P < .51). In contrast, magnetic resonance imaging (MRI) was described as "always" or "often" necessary in 28 of 71 (39%) of the surveys, significantly less than CT (P < .0001). There was no statistical impact of practice specialization on ordering of serum tests (P = .25) or imaging (P = .50 for CT; P = .46 for CXR; P = .45 for MRI). Following analysis of 1,510 vocal fold paralysis abstracts, 19 publications were found to be appropriate for an EBM review of serum testing with 15 available for review of radiographic imaging. Only one study presented level III evidence; the remainder were levels IV and V comprised of retrospective series and case reports. The evidence supporting serum or radiographic testing toward the evaluation of idiopathic vocal fold paralysis is given an overall grade of "C."

CONCLUSIONS

Serum and radiographic testing for the evaluation of vocal fold paralysis is supported by grade "C" evidence only. There are no existing prospective studies estimating the clinical impact of testing on diagnosis or patient outcome. Current practice, as estimated by a survey of the ABEA membership, is not well founded for serum testing and only by retrospective case series with regard to imaging. Further study into the nature of idiopathic vocal fold paralysis and outcomes assessment of diagnostic paradigms may improve clinical practice.

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.

Clinical evaluation of vocal fold paralysis

Vocal fold paralysis is regarded as a sign of other pathologic findings until investigation has proven that there is no lesion to explain the paralysis. We have outlined a cost-effective and time- and labor-efficient method for the clinical evaluation of vocal fold paralysis, including a focused history; vocal capability assessment to find deficits in the function of palate,pharynx, and larynx: and, finally, an intense examination under topical anesthesia to demonstrate these deficits. In essence, it is the endoscopic version of a radiographic study from the skull base through the aortic arch. This method is streamlined as compared with prior protocols for evaluation of vocal fold paralysis, because it directs the necessary further workup according to the likely site of the lesion as indicated by the extended physical examination and can be conducted entirely in the physician's office. Radiographic workup should include CT of the skull base through the upper mediastinum if solely a recurrent nerve paralysis is present; it should include MRI of the skull base if high vagal signs and symptoms are present. If MRI is negative, CT may also be needed for complete evaluation. Neurologic signs that are not all ipsilateral require MRI of the brain and consultation with a neurologist. Esophageal obstruction combined with vocal fold paralysis mandates evaluation via esophagoscopy or an esophagram.

Using MR imaging to predict invasion of the recurrent laryngeal nerve by thyroid carcinoma

OBJECTIVE

We evaluated the accuracy of MR imaging findings for predicting invasion of the recurrent laryngeal nerve by thyroid carcinoma and established an optimal criterion on which to base this prediction.

MATERIALS AND METHODS

We reviewed MR imaging findings (lesion size and posterior extension of tumor; encirclement of and invasion into the laryngeal cartilage, trachea, and esophagus by the tumor; and the amount of effaced fatty tissue in the tracheoesophageal groove or between the laryngeal cartilage and hypopharyngeal wall) in 66 patients with thyroid carcinoma. The amount of effaced fatty tissue was classified as one of five grades: 1, normal amount of fatty tissue; 2, partly effaced; 3, completely effaced in one MR imaging slice; 4, completely effaced in two contiguous MR slices; and 5, completely effaced in three or more contiguous MR slices.

RESULTS

Thirty-two (48%) of the 66 patients had surgically or pathologically verified recurrent laryngeal nerve invasion. Logistic modeling revealed that the amount of effaced fatty tissue (p < 0.001) and the lesion size (p = 0.033) were the significant factors. Using the threshold values for the lesion size to predict invasion, we found that a threshold of more than 2.9 cm showed the highest accuracy, 76%, with 78% sensitivity and 74% specificity. For the amount of effaced fatty tissue, a grade of 3 or more had the highest accuracy, 88%, with 94% sensitivity and 82% specificity. Addition of the lesion size to this criterion did not improve the diagnostic accuracy of using the amount of effaced fatty tissue alone.

CONCLUSION

Invasion of the recurrent laryngeal nerve by thyroid carcinoma was accurately predicted by the finding of effaced fatty tissue on MR imaging.

Case report: bilateral vocal cord paralysis caused by cervical spinal osteophytes

Thyroid and cervical surgery, tracheal intubation, trauma and neurodegenerative and neuromuscular diseases may cause bilateral vocal cord paralysis. There are only a few reported cases of bilateral cord paralysis associated with cervical hyperostosis in the English literature. We report the MR and CT findings of a case of bilateral vocal cord paralysis caused by cervical spinal osteophytes compressing the recurrent laryngeal nerves.

Imaging of the glossopharyngeal, vagus, and accessory nerves

The origination and course of the glossopharyngeal, vagus and accessory cranial nerves explains their function and localizes pathology. Abnormalities of these lower cranial nerves may be intrinsic or extrinsic and is due to a multiplicity of disease processes. The clinical presentation of the involved cranial nerve helps to guide imaging evaluation. Magnetic resonance imaging without and with contrast is the mainstay of imaging of cranial nerves IX, X and XI pathology, but computed tomography provides substantial information as well.

Utility of helical computed tomography in the study of arytenoid dislocation and arytenoid subluxation

Conventional computed tomography (CT) has been considered a mainstay in the evaluation of the larynx. A major difficulty with utilizing this modality, especially in the study of the arytenoid, is the time necessary to perform a thin-slice examination through a structure that has a propensity to move with respiration and swallowing. Helical CT not only significantly reduces the time necessary to study the larynx, but enables one to perform multiple high-resolution multiplanar reconstructions. Eleven patients with arytenoid abnormalities documented by strobovideolaryngoscopy or direct laryngoscopy were imaged with helical CT. A comprehensive radiographic examination illustrating the cricoarytenoid relationship in all of the subjects was completed in less than 20 seconds by using axial reconstructions in 2-mm-thick slices at 1-mm intervals, with subsequently derived sagittal and coronal reconstructions. Helical CT may be a useful adjunct in the diagnosis of arytenoid subluxation or dislocation.

Parapharyngeal vagal neurilemmoma extending to the jugular foramen

A large vagal neurilemmoma in a 33-year-old man is reported. He complained of slowly progressive palsy of the tongue on the left side. Weakness of soft palate movement was also noted. Magnetic resonance imaging (MRI) revealed a tumour in the left parapharyngeal space with partial extension to the posterior cranial fossa through the jugular foramen. Carotid angiography revealed avascularity of the tumour and anterior shift of the left internal carotid artery. The venous phase showed no blood flow in the internal jugular vein. The tumour was successfully extirpated via a transmandibular transpterygoid approach. Although vagus nerve dysfunction was not observed pre-operatively, the tumour was identified as a neurilemmoma arising from the vagus nerve. The surgical approach should be selected according to the lesion in individual patients. Since neurilemmoma is benign in nature, minimal post-operative sequelae should be expected.

Contemporary evaluation of unilateral vocal cord paralysis

Unilateral vocal cord paralysis is a common finding in the practice of otolaryngology. Multiple etiologies have been described and have not changed appreciably in the last century. We attempted to characterize the contemporary evaluation of unilateral vocal cord paralysis, with consideration given to cost-effectiveness. Thirty-one board-certified otolaryngologists were interviewed to determine their typical evaluation protocol. The average cost of an evaluation totaled $1706.18, with a range of $112.56 to $3439.52. Otolaryngologists with more years of experience tended to pursue briefer and less expensive evaluations. The charts of 187 patients with a diagnosis of vocal paralysis from 1983 to 1991 were reviewed, of which 113 were evaluable. Eighty-four of these 113 (74%) were unilateral. In 48 of 84 cases (57%), the cause was apparent at the time of diagnosis. In 36 of 84 cases (43%), an evaluation was necessary. A diagnosis was achieved in 27 of these 36 instances (75%), with the most useful test being a chest roentgenogram (n = 13, 48%). The most common cause of unilateral vocal cord paralysis in our series was neoplasm (n = 34, 40%), followed by surgical trauma (n = 29, 35%). In no instance was a malignancy discovered subsequent to the initial evaluation. The most cost-efficient, inclusive diagnostic evaluation of unilateral vocal cord paralysis involves a stepwise progression through the tests that are most likely to yield a diagnosis, with endoscopy reserved for those cases in which simpler, less invasive tests have not indicated a cause.

Arytenoid subluxation: diagnosis and treatment

Both arytenoid subluxation and recurrent laryngeal nerve paralysis (RLNP) may result from injury to the larynx, and they may be difficult to distinguish clinically. A patient with arytenoid subluxation who was initially believed to have RLNP was treated with medialization laryngoplasty 1 year after the injury. Preoperative magnetic resonance imaging and computed tomography effectively demonstrated the cricoarytenoid subluxation, which was confirmed by intraoperative electromyography (EMG) showing normal electrical activity in the thyroarytenoid muscle. Photographs from preoperative fiberoptic laryngoscopy are presented to identify the appearance of arytenoid subluxation. Computed tomographic findings and photographs from laryngoscopy of two patients with RLNP documented by intraoperative EMG evaluation are presented to help distinguish the clinical appearance of this disorder from arytenoid subluxation. An integrated approach to the diagnosis and treatment of arytenoid subluxation is presented.