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Sympathetic chain schwannomas

Cervical sympathetic chain schwannomas (SCSC) are rare benign nerve sheath tumors that typically present in middle-aged patients with a neck mass or dysphagia due to mass effect. They are detected either incidentally or when causing compression symptoms.

Key Images

Sympathetic chain schwannoma

Lesion is right post-styloid parapharyngeal space, medial to the carotid space.

The lesion measures 4 x 2.4 x 2.6 cm (CC x AP x ML), over C1-C3 levels.

No evidence of flow voids within the lesion.

The lesion is longitudinally oriented without neural foraminal extension.

There is no arterial phase enhancement. In the delayed phase, the lesion shows homogeneous enhancement.

The lesion displaces the internal carotid artery and internal jugular vein laterally (in the same direction) without separating nor encasing the vessels. — Sympathetic chain schwannoma

Look For First

Longitudinally oriented mass in the perivertebral space at C1-6 level arising from the superior or middle sympathetic ganglia
Anterolateral displacement of carotid space structures (ICA, ECA, IJV) without splaying of carotid vessels or separation of artery/vein
Vagus nerve can be followed as a distinct structure separate from the tumor mass

Key Image Findings

On MRI T1-weighted imaging: isointense or hypointense signal intensity mass in the perivertebral space
On MRI T1 with gadolinium: intense enhancement, particularly on delayed sequences, characteristic of schwannoma
On MRI T2-weighted imaging: heterogeneously hyperintense signal with no significant flow voids, reflecting varying cellularity typical of Antoni A tissue predominance
Location in the upper or mid perivertebral space from C1-6, arising specifically from superior or middle cervical sympathetic chain ganglia
Mass effect characterized by anterolateral displacement of adjacent carotid space vessels without splaying of the carotid bifurcation or arteriovenous separation
On CT: hypoattenuated on unenhanced images with mixed degree of enhancement compared to skeletal muscle, though CT is less sensitive than MRI
The tumor maintains an eccentric origin without aggressive invasion into adjacent structures, allowing for potential conservative management
Absence of significant neural compression symptomatology despite location, as the sympathetic chain resides in a loose fascial plane

Differential Diagnosis

Vagal schwannoma: differentiated by pattern of displacement of carotid space structures and ability to trace vagus nerve separately from the tumor
Carotid body tumor/paraganglioma: distinguished by characteristic T2 flow voids ('salt and pepper' appearance) and arterial enhancement pattern
Metastatic lymph node: lacks the characteristic schwannoma signal intensity and enhancement pattern on MRI
Spinal nerve sheath tumors: differentiated by location in perivertebral space versus intraforaminal or more posterior spinal location
Minor salivary gland tumors: these occur in the parapharyngeal space, not in the perivertebral space where sympathetic chain schwannomas arise

Discussion

Sympathetic chain schwannomas are typically of the cellular subtype with predominant Antoni A tissue histology, contributing to their heterogeneous T2 appearance

The location and specific displacement pattern of carotid space structures is the key radiological feature to differentiate SCSC from vagal schwannomas

Horner syndrome is rare but has been reported as a complication, and transient postoperative Horner syndrome can occur following surgical treatment

The loose fascial plane surrounding the sympathetic chain explains the rarity of neural compression despite the presence of significant mass effect

Surgical resection is the treatment of choice, but observation is a reasonable option given the benign nature and eccentric origin without aggressive invasion

These tumors typically present in middle-aged patients with a median age around 41 years, and most present with mass effect symptoms such as neck mass or dysphagia

Reporting Pearls

Describe the tumor as a well-defined mass in the perivertebral space at the level of the cervical sympathetic chain (specify superior or middle ganglion if apparent), with anterolateral displacement of carotid space structures while preserving the relationship between the internal carotid artery and internal jugular vein, and note the ability to trace the vagus nerve as a distinct structure separate from the mass.

Pitfalls

Confusing sympathetic chain schwannoma with vagal schwannoma: the key differentiator is that SCSC causes anterolateral displacement of carotid structures without splaying, whereas vagal schwannomas typically separate the vascular structures
Misidentifying the mass as a carotid body tumor: carotid body tumors show characteristic T2 flow voids and typically enhance from arterial supply, not the homogeneous enhancement pattern of schwannomas
Overlooking the specific location in the perivertebral space at C1-6 level: minor salivary gland tumors occur in the parapharyngeal space and would not have this characteristic location
Over-interpreting the mass effect as indicating aggressive behavior: the eccentric origin and loose fascial plane of the sympathetic chain allow for conservative observation without the need for immediate surgical intervention

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