Spinal schwannomas are schwannomas arising from nerves within the spinal canal. They are the most common intradural extramedullary spinal tumors, representing 30% of such lesions. They are most frequently seen in the cervical and lumbar regions, far more frequently than in the thoracic spine.
On imaging, they are usually characterized as solid and well-defined lesions with low T1 and high T2 MRI signals, and showing contrast enhancement. The signal intensity can be heterogeneous due associated hemorrhage, intrinsic vascular changes (thrombosis, sinusoidal dilatation), cyst formation and fatty degeneration.
This article specifically relates to spinal schwannomas. For a general discussion of schwannomas (epidemiology, pathology and general radiographic features), refer to schwannoma and spinal nerve sheath tumors.
Patients commonly present with pain. As spinal schwannomas usually arise from the dorsal sensory roots, radicular sensory changes also occur. Weakness is less common. Myelopathy may occur if the lesion is large.
Most spinal schwannomas are solitary and sporadic. However, there is an association with neurofibromatosis type 2 (NF2). In patients with NF2, almost all spinal nerve root tumors are schwannomas or mixed tumors.
Schwannomas are in most instances indistinguishable from neurofibromas. As such, please refer to the article on spinal nerve sheath tumors for a discussion of their radiographic appearance.
In general, schwannomas appear as rounded lesions, often with associated adjacent bony remodelling. When large they may either align themselves with the long axis of the cord, forming sausage shaped masses which can extend over several levels, or may protrude out of the neural exit foramen, forming a dumbbell shaped mass.
Although neurofibromas and schwannomas can look identical, schwannomas are frequently associated with hemorrhage, intrinsic vascular changes (thrombosis, sinusoidal dilatation), cyst formation and fatty degeneration. These findings are rare in neurofibromas 8.
Signal characteristics include 9:
- T1: 75% are isointense, 25% are hypointense
- T2: more than 95% are hyper intense, often with mixed signal
- T1 C+: virtually 100% enhance
Treatment and prognosis
Schwannomas are slow growing lesions but can nevertheless be debilitating. They almost never undergo malignant change. Surgery is the treatment of choice. Gross total resection is usually curative for patients with sporadic tumors. For patients with NF2, there is a high incidence of new tumor formation.
The main differentials are:
For a discussion of helpful distinguishing features, please refer to spinal nerve sheath tumors.
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