Sonographic diagnosis of a cervical vagal schwannoma

Normal anatomy, variants and factors associated with the cervical vagus nerve topography: a high-resolution ultrasound study

PURPOSE

To describe the cervical vagus nerve (CVN) topography at the thyroid lobe (TL) level using high-resolution ultrasound and to investigate the possible association with anthropometric data, TL size, and thyroid disease.

METHODS

We prospectively examined 550 CVNs in 275 (205 female, 70 male) individuals with normal thyroid (53/275, 19.3%), multinodular disease (167/275, 60.7%), and Hashimoto thyroiditis (55/275, 20%). The CVN location relative to the common carotid artery was recorded as typical (lateral position) and atypical (anterior, medial, and posterior position). The shortest distance between CVN and TL margin, the TL dimensions, and volume were measured.

RESULTS

Normal thyroid subjects had lateral-positioned right CVNs in 100% and lateral/anterior/medial left CVNs in 81.1%, 15.1%, and 3.8%, respectively. CVN types did not differ significantly bilaterally between study groups. Asymmetry in CVN topography in all subjects was found in 22.2%, of which anterior CVN was the most common atypical position (64%), especially on the left side (82%). Significant gender, age, body mass, and BMI differences among CVN types were observed on the left side only. Among CVN types, no difference in TL dimensions, volume, and CVN-TL distance was found in all study groups. A weak negative correlation was recorded between CVN-thyroid distance and TL volume only on the left side (r = - 0.147, p = 0.01).

CONCLUSION

Asymmetry in CVN topography is mainly due to the increased incidence of the anterior location of CVN on the left side. Age and anthropometric parameters are different on the left side possibly due to the increased prevalence of left CVN variants.

Transcutaneous Sonography for Detection of the Cervical Vagus Nerve

Cervical vagus nerve is not identified by computed tomography or magnetic resonance imaging. Transcutaneous sonography may be the best imaging study to evaluate the cervical vagus nerve. A 7 to 18 MHz linear array transducer was placed transversely on the lateral neck focusing on the carotid sheath from the clavicle level upward to the digastric muscle level bilaterally. The gray-scale technique was used, with the scan setting for the thyroid gland. Between January 2015 and March 2016, 314 patients with 628 cervical vagus nerves were enrolled, including 104 men and 210 women. Their ages ranged from 14 to 84 years. Transcutaneous sonography identified the entire trunk of bilateral cervical vagus nerves in 254 (80.9%) patients and did not identify 1 or both cervical vagus nerves in the other 60 (19.1%) patients. Among 628 cervical vagus nerves, transcutaneous sonography identified 626 (99.6%) lower cervical vagus nerves and 551 (87.7%) upper cervical vagus nerves. Among 551 visible upper cervical vagus nerves, 495 (89.8%) nerves were located laterally, 17 (3%) nerves were located medially, 9 (1.6%) nerves were located anteriorly, and 30 (5.4%) nerves were located posterior to the internal carotid artery. Man and left-side nerve were the factors associated with the anatomical variation in the upper cervical vagus nerve. Transcutaneous sonography can be the best imaging study to show the cervical vagus nerve and may be helpful to evaluate the nerve before neck operation.

Phantom Nodules Detected by Ultrasound Examination of the Neck: The Possibility of Ectopic Cervical Thymic Tissue in Adults

Purpose

The aim of this study was to investigate the ultrasound characteristics and clinical significance of slightly hyperechoic lesions, referred to as phantom nodules, in the perithyroidal area in patients.

Materials and Methods

A total of 128 patients who underwent thyroidectomy with central neck lymph node dissection at Kuma Hospital in Hyogo, Japan were included in the study. We detected 16 phantom nodules during preoperative ultrasound examinations, defined as slightly hyperechoic masses located in the perithyroidal areas, in 13 of these 128 patients (10.2%; mean age: 55.6 years, range: 36–75 years).

Results

All phantom nodules were located in the caudal region of the thyroid gland, and the mean maximum dimension was 7.2 mm. 12 of the 16 nodules were round or oval, while the remaining 4 were fusiform and molded by the surrounding tissue. All nodules were well-defined, solid, homogeneous, hyperechoic masses. No speckled echo pattern, internal linear echo, or vascular flow signal was observed. All 4 nodules subjected to histological examination were composed of ectopic thymic tissue. In 2 of these 4, the parenchyma was severely involuted and almost entirely replaced by adipose tissue.

Conclusion

To the best of our knowledge, this is the first report wherein some of the detected hyperechoic perithyroidal masses were composed of ectopic thymic tissue, and some were primarily composed of adipose tissue that completely replaced involuted ectopic thymic tissue. The results of the study suggest that these so-called phantom nodules are clinically insignificant and do not require fine needle aspiration cytology or further investigation.

Ultrasonography-Based Thyroidal and Perithyroidal Anatomy and Its Clinical Significance

Ultrasonography (US)-guided procedures such as ethanol ablation, radiofrequency ablation, laser ablation, selective nerve block, and core needle biopsy have been widely applied in the diagnosis and management of thyroid and neck lesions. For a safe and effective US-guided procedure, knowledge of neck anatomy, particularly that of the nerves, vessels, and other critical structures, is essential. However, most previous reports evaluated neck anatomy based on cadavers, computed tomography, or magnetic resonance imaging rather than US. Therefore, the aim of this article was to elucidate US-based thyroidal and perithyroidal anatomy, as well as its clinical significance in the use of prevention techniques for complications during the US-guided procedures. Knowledge of these areas may be helpful for maximizing the efficacy and minimizing the complications of US-guided procedures for the thyroid and other neck lesions.

Neuromuscular ultrasound of cranial nerves

Ultrasound of cranial nerves is a novel subdomain of neuromuscular ultrasound (NMUS) which may provide additional value in the assessment of cranial nerves in different neuromuscular disorders. Whilst NMUS of peripheral nerves has been studied, NMUS of cranial nerves is considered in its initial stage of research, thus, there is a need to summarize the research results achieved to date. Detailed scanning protocols, which assist in mastery of the techniques, are briefly mentioned in the few reference textbooks available in the field. This review article focuses on ultrasound scanning techniques of the 4 accessible cranial nerves: optic, facial, vagus and spinal accessory nerves. The relevant literatures and potential future applications are discussed.

Imaging findings of neurogenic tumours in the head and neck region

OBJECTIVE

The aim of this study was to describe the CT, MRI and ultrasonography findings of five cases of neurogenic tumours in the head and neck region.

METHODS

Five neurogenic tumours were analysed with respect to their CT value, the presence of cystic change, target sign, lobulation, connection to the nerve and vascularity.

RESULTS

The contrast-enhanced CT (ECT) of the schwannomas demonstrated either a mass with low enhancement (two out of three cases), which reflected the predominant Antoni B components, or a mass with cystic changes, which was an Antoni A-based schwannoma displaying cystic changes (one out of three cases). On MRI, all tumours showed homogeneous and isointense signals for muscle on T₁ weighted images (T₁ WIs). T₂ weighted images (T₂ WIs) and gadolinium (Gd)-enhanced T₁ WIs demonstrated target sign in both schwannomas. Ultrasound examination showed a well-defined, ovoid or round hypoechoic mass. The direct connection to the nerve was demonstrated in two of the five cases. Lobulation was observed in only one of the five cases and cystic changes were observed in one of the five cases. In all of the cases, no vascularity was seen in power Doppler images (PDIs) obtained percutaneously.

CONCLUSIONS

Low-enhanced areas on ECTs can be specific for schwannomas, which suggests the predominance of Antoni B components. The target sign on T₂ WIs and Gd-enhanced T₁ WIs can be specific, which can be used to differentiate the two different components (Antoni A and Antoni B). The direct connection to the nerve can be a specific finding for neurogenic tumours; however, at present the sensitivity is 40%.