CASE 17778 Published on 19.07.2022

Retropharyngeal Schwannoma

Section

Head & neck imaging

Case Type

Clinical Cases

Authors

Ana Germano, Carolina Durão, João Rito, Gustavo Rocha, Maria Gabriela Gasparinho, Filipe Freire

Hospital Professor Doutor Fernando Fonseca, EPE, Amadora, Portugal

Patient

54 years, female

Categories
Area of Interest Ear / Nose / Throat, Head and neck ; Imaging Technique CT, MR
Clinical History

A 54-year-old woman presented with a 2-week history of throat foreign body sensation, and dyspnoea. On physical examination, her breathing was noisy. She denied pain and fever. Nasopharyngoscopy detected an airway lumen stenosis caused by a hypopharynx submucosal mass. Past history and lab tests were unremarkable except for thyroid nodules.

Imaging Findings

Neck CT before and after intravenous contrast reveals a lesion in the infrahyoid retropharyngeal space, extending from the level of the free edge of the epiglottis, above, to the glottis level below. It is well-defined, oval, hypodense, without calcifications, with moderate enhancement after intravenous contrast. A thin peripheral rim of fat can be found separating the lesion from the posterior pharyngeal wall anteriorly, and from the prevertebral muscles posteriorly. The cervical oesophagus originates below the lesion and has no relation with it.

Neck MRI (T1 before and after gadolinium, fat-suppressed T1, and T2 sequences in the axial, sagittal and coronal planes) was performed. The oval retropharyngeal lesion is isointense to the muscles on T1, with vivid enhancement after gadolinium. It is heterogeneously bright on T2, where we can also identify multiple small, ring-like structures with peripheral hyperintensity.

A transoral approach was used to surgically remove the lesion.

Discussion

Background

The retropharyngeal space (RPS) extends from the skull base to the mediastinum (between the T2 and T6 vertebral bodies). It is bounded anteriorly by the buccopharyngeal fascia, posteriorly by the alar fascia, and divided in supra-hyoid and infra-hyoid compartments. The first contains fat and lymph nodes, the second contains only fat [1,2,3]. The most frequent lesions in this space are infectious (abscesses, cellulitis), metastatic lymph nodes, or direct invasion from pharyngeal mucosal space carcinoma. Occasionally tortuous carotid arteries, or bulging from vertebral osteophytes can be seen. There are only sporadic reports of primary tumours of the RPS (lipomas, neuroblastomas, pleomorphic adenomas, schwannomas). Schwannomas are exceedingly rare in this space and are thought to originate from small branches of the pharyngeal nerve plexus [1,4,5].

Clinical Perspective

Schwannomas are benign, slow-growing lesions, symptomatic when they grow. Reported symptoms at diagnosis include snoring, foreign body sensation and progressive dysphagia [1-4,6,7]. Nasopharyngoscopy usually shows a posterior submucosal bulging with intact mucosa. Sectional imaging is needed to further characterize the exact location, boundaries, relation with adjacent structures and intrinsic characteristics of these lesions. Assessment of the relation with the carotid arteries, vertebrae, and possible invasion of neighbouring structures is crucial to plan the surgical approach [1-7].

Imaging Perspective

CT and MRI are the imaging modalities of choice. Key findings include an oval or fusiform-shaped lesion, with well-defined margins, hypodense on CT, iso or hypointense on T1-weighted and hyperintense on T2-weighted MRI sequences, that enhances after contrast media administration. A thin rim of fat surrounding the lesion is often found (split fat sign), as well as several little ring-like forms with outlying high signal on T2 (fascicular sign [8].

The final diagnosis is made by histopathology.

Outcome

Complete surgical resection is the therapy of choice. Surgical approach is chosen based on the size and location of the lesion. Prognosis is excellent with a complete recovery usually achieved in a short period of time.

Take-Home Message

  • Retropharyngeal schwannoma is a challenging diagnosis.
  • CT and MR can suggest the diagnosis and assist the differential diagnosis with infections, vascular or malignant lesions.
  • Key-imaging findings are the oval/fusiform shape, low density on CT, iso or low signal on T1, high signal on T2, contrast enhancement, presence of split fat sign and/or fascicular sign.

Written informed patient consent for publication has been obtained

Differential Diagnosis List
Retropharyngeal schwannoma
Hypopharyngeal carcinoma
Metastatic lymph node
Abscess
Aberrant Internal carotid artery
Final Diagnosis
Retropharyngeal schwannoma
Case information
URL: https://www.eurorad.org/case/17778
DOI: 10.35100/eurorad/case.17778
ISSN: 1563-4086
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