Sympathetic chain schwannoma

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Sympathetic chain schwannomas or schwannomas of the cervical sympathetic chain (SCSC) are rare benign nerve sheath tumors. These longitudinally oriented tumors in the perivertebral space rely on anatomical mass effect to differentiate from the main differential masses of vagal schwannoma or spinal schwannoma.

This article specifically relates to sympathetic chain schwannomas. For a general discussion of schwannomas, refer to the main article: schwannoma.

Epidemiology

There are only case reports or limited small series of sympathetic chain schwannomas. A 12-case review reported a median age of 41 years , similar to other reports and schwannomas in general.

Clinical presentation

Although some are detected in asymptomatic patients, most patients will present with mass effect e.g. neck mass , dysphagia. Neural compression is rare as the sympathetic chain is in a loose fascial plane , however, Horner syndrome has been reported.

Pathology

Please refer to the generic article on schwannomas for a discussion of pathology. SCSCs are typically of the cellular subtype, with predominant Antoni A tissue.

SCSCs tend to arise from the superior or middle ganglia of the sympathetic chain.

Radiographic features

The main feature to help identify a sympathetic chain tumor is the location and mass effect on adjacent vessels. SCSCs will arise from the superior or middle ganglia of the cervical sympathetic chain (from C1-6), in the upper/mid perivertebral space. These tumors will displace the carotid space structures (ICA, ECA, IJV and vagus nerve) anterolaterally, usually without splaying of the carotid vessels nor separation of the arteries and vein . Also, the vagus nerve can be followed distinctly from the tumor.

CT

CT is not as sensitive or specific as MRI for schwannoma diagnosis. Imaging features include :

hypoattenuated on unenhanced CT
mixed degree of enhancement compared to skeletal muscle

MRI

SCSCs have signal characteristics shared with typical schwannomas:

T1: isointense or hypointense
T1 C+ (Gd): intense enhancement (especially on delayed sequences)
T2: heterogeneously hyperintense (due to varying degree of cellularity), no significant flow voids

Treatment and prognosis

Surgery is the treatment of choice, but allowing for symptoms observation of these schwannomas is also an option given the eccentric origin and lack of aggressive invasion. Transient postoperative Horner syndrome has been reported .

Differential diagnosis

vagal schwannoma: differentiate due to the effect on adjacent vessels
carotid body tumor / paraganglioma: typically T2W flow voids (salt and pepper) and arterial enhancement
metastatic lymph node
minor salivary gland tumors: present in the parapharyngeal space, but not in the perivertebral space

For a discussion of helpful distinguishing features, please refer to spinal nerve sheath tumors.