High-Resolution Ultrasound for Diagnostic Assessment of the Great Auricular Nerve – Normal and First Pathologic Findings

Abstract

Purpose: The great auricular nerve (GAN) is a sensory branch of the superficial cervical plexus. While its blockade is an established procedure, little is known about the ultrasound appearance of pathologic conditions of the GAN itself. We, therefore, aimed to evaluate the possibility of the visualization and diagnostic assessment of the GAN along its entire course by means of high-resolution ultrasound (HRUS).

Materials and Methods: To assess the feasibility of visualization, we performed HRUS with an 18 MHz probe, HRUS-guided, fine-needle ink markings and consecutive dissection in six anatomical specimens. Then, we measured the diameter of the GAN in healthy volunteers and finally performed a retrospective review of patients referred for HRUS examinations because of pain within GAN territory between August 1, 2012 and August 1, 2013.

Results: The GAN was clearly visible with HRUS from its formation to the final branches, and was marked successfully on both sides in all anatomical specimens (n = 12). The mean average in-vivo was 0.14 cm ± 0.03 (range 0.08 – 0.2). Seven cases of patients with GAN pathologies of various origins (idiopathic, traumatic, tumorous and iatrogenic) were identified, of which 6 were visible on HRUS and all of which could be confirmed by complete resolution of symptoms after selective HRUS-guided GAN block.

Conclusion: This study confirms the reliable ability to visualize the GAN with HRUS throughout its course, both in anatomical specimens and in vivo. The provided cases show that pathologies of the GAN seem to have a variety of causes and may not be rare. We, therefore, encourage the use of HRUS in patients with unclear pain in the auricular, periauricular and posterior-lateral head.

Zusammenfassung

Ziel: Der Nervus auricularis magnus (GAN) ist ein sensibler Ast des Plexus cervicalis superficialis. Während seine Blockade eine etablierte Methode ist, ist wenig bekannt über die sonografische Darstellung pathologischer Zustände des GAN selbst. Ziel dieser Studie war es, Visualisierbarkeit und diagnostisches Potential des hochauflösenden Ultraschalls (HRUS) im gesamten Verlauf des GAN zu evaluieren.

Material und Methoden: Zur Klärung der Visualisierbarkeit wurde eine HRUS-gezielte Markierung der GAN und anschließende Sektion in sechs anatomischen Präparaten durchgeführt. Danach wurde der Durchmesser des GANs bei 10 gesunden ProbandInnen vermessen. Zusätzlich erfolgte eine retrospektive Analyse der PatientInnen, die zwischen 1. August 2012 und 1. August 2013 aufgrund von Schmerzen im Bereich des GAN untersucht wurden.

Ergebnisse: Der GAN konnte von seiner Formierung bis in die Endäste verfolgt werden und wurde in allen anatomischen Präparaten erfolgreich markiert (n = 12). Der mittlere Durchmesser in-vivo war 0,14 cm ± 0,03 (0,08 – 0,2 cm). Sieben PatientInnen mit GAN-Pathologien unterschiedlicher Genese wurden identifiziert (idiopathisch, traumatisch, tumor-assoziiert und iatrogen), von denen 6 mittels HRUS visualisiert werden konnten und alle durch vollständige Remission der Schmerzen nach HRUS-gezielter, selektiver Blockade des GAN bestätigt werden konnten.

Schlussfolgerungen: Diese Studie bestätigt die Visualisierbarkeit des GAN sowohl im anatomischen Präparat als auch in vivo. Die präsentierten Fälle zeigen, dass das breite Spektrum möglicher Pathologien des GAN wesentlich häufiger sein könnte als angenommen. Wir empfehlen eine HRUS-Abklärung bei PatientInnen mit Schmerzen im Bereich des Ohres, periaurikulär und poster-lateralen Kopfes.

Key words

head/neck - ear - great auricular nerve - neuroma - neuropathic pain

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