39 Peripheral Nerve Sheath Tumors of the Second Cervical Nerve: Anatomical Correlates and Surgery

10.1055/b-0034-81416

39 Peripheral Nerve Sheath Tumors of the Second Cervical Nerve: Anatomical Correlates and Surgery

Goel, Atul, Dange, Nitin

Peripheral nerve sheath tumors arising from the second cervical nerve root are relatively common and constitute ∼15% of all spinal peripheral nerve sheath tumors. In our series, out of the total spinal peripheral nerve sheath tumors seen during the period of 1992 to 2006, 24% arose from the second cervical root.1 There are several isolated reports and some relatively large series of cases with C2 peripheral nerve sheath tumors published in the literature.1–5 Spinal peripheral nerve sheath tumors are seen sporadically in the general population, but they are frequently associated with neurofibromatosis types 1 and 2 (NF1 and NF2).5,6 An intraspinal location is the most frequent form, whereas an extraspinal component accounts for 15% of all cervical peripheral nerve sheath tumors. Some authors have noted a predominance of “extradural” location of peripheral nerve sheath tumors at the C2 vertebral level.

Despite their critical location, with extension of the tumor anterior or anterolateral to the cord and proximity to vital neural structures and the vertebral artery, surgery on C2 peripheral nerve sheath tumors constitutes one of the most gratifying experiences. If the anatomy of the tumor and its relationship to normal structures in the vicinity is appropriately understood, the surgery on these formidable-looking tumors is relatively straightforward.1,7–9 The majority of peripheral nerve sheath tumors located at the level of C2 probably arise from the large C2 ganglion and are limited within the dural confines or are “interdural” in nature. In contrast to other spinal peripheral nerve sheath tumors, the location of C2–peripheral nerve sheath tumors is, in most cases, posterior to the lateral mass of the atlas and axis and the atlantoaxial joint and is exposed to the posterior without any bony cover ( Figs. 39.1 and 39.2 ). Radical tumor resection is safe, resolution of clinical symptoms is rapid, and recurrence rates are extremely low. In select cases, bone work for tumor exposure and resection can be entirely avoided.

Multiplicity of peripheral nerve sheath tumors is frequently seen in patients with von Recklinghausen disease. George and Lot reported 4% multiplicity of peripheral nerve sheath tumors at any spinal level.4 The dural anatomy of tumors associated with von Recklinghausen disease is not different from other C2 peripheral nerve sheath tumors, but the tumors in general are more firm in consistency and well defined in nature.

**Fig. 39.1a, b** a Cadaveric dissection specimen of the C1–C2 region, showing the C2 ganglion and its relationships with the C1–C2 joint, vertebral artery, and dural tube. The vertebral artery on the side of ganglion is rudimentary in nature. The ganglion on the right side has been sectioned off to show the joint. b Drawing showing the C2 ganglion and its relationships.

**Fig. 39.2 Drawing showing the proposed classification of the tumors into types A, B, and C. Type A is intradural, and types B and C are “interdural” in nature.**

Clinical Features

We evaluated our series of 60 patients with C2 peripheral nerve sheath tumors.1 Symptoms and signs and radiological characteristics were usually diagnostic in nature. However, unusual symptoms of syncopal attacks, migrainous headaches, and unrelated motor and sensory symptoms can lead to misdiagnosis. The mean age of the patients was 28 years (range 6–62 years). There were 38 men and 22 women. The mean duration of symptoms at the time of presentation was 27 months (range 4 days–5 years). Mild to moderate myelopathy was present in 52 cases. None of the patients presented with severe myelopathy. All patients were able to walk unaided at the time of admission. The rest of the patients had either local symptoms, such as neck pain, or symptoms essentially unrelated to C2 peripheral nerve sheath tumor. In two of our patients with von Recklinghausen disease, the bilateral C2 peripheral nerve sheath tumors were large and had caused severe cord compression, but the presenting symptoms seemed unrelated to the C2 peripheral nerve sheath tumors and were related instead to other tumors in the spine or the brain.

Anatomical Features of C2 Peripheral Nerve Sheath Tumors

C2 is the largest ganglion of all the spinal roots. Its location is unique, as it is found outside the spinal canal exposed over the lateral mass of the axis and under the lateral aspect of the posterior arch of the atlas. Tumors located there are slow growing and usually acquire a large size before becoming symptomatic. Characteristic dumbbell-shaped C2 peripheral nerve sheath tumors having both intraspinal and paraspinal components have been reported. Dumbbell tumors located elsewhere in the spine are generally classified as intraspinal, foraminal, and extraforaminal. Depending on the anatomical location as identified during surgery, peripheral nerve sheath tumors of the C2 nerve are divided into three groups ( Fig. 39.2 ). Those located within or extending into the spinal dural tube are called type A, those located within the dural tube of the C2 ganglion are labeled as type B, and tumors extending lateral into the paraspinal region are labeled as type C. Type C tumors are those that extend outside the limits of the spine and into the paraspinal spaces. The line of demarcation between type B and type C is set by an arbitrary vertical line drawn between the tips of the transverse processes of the atlas and axis. In the classification used in this series, type A was intradural, and type B and type C were interdural. Although it is possible to correlate the described classification with preoperative investigation in most cases, in some cases it may be impossible to decipher if the peripheral nerve sheath tumor has an intradural extension or not. Of the 60 patients with 64 C2 peripheral nerve sheath tumors, there were 5 pure type A tumors, 7 type A B tumors, 31 type B tumors, and 21 type B C tumors ( Figs. 39.3, 39.4, 39.5, 39.6, 39.7, and 39.8 ). The tumors varied in size, ranging from 10 to 76 mm (average 31 mm). Sixteen tumors were 25 mm in its maximum diameter. Considering the location and extension, it appeared that the majority of peripheral nerve sheath tumors probably arise from the C2 ganglion and extend either toward the spinal dural tube or away from it into the paraspinal region. In the majority of cases, it was observed that although the tumors had a large intraspinal extension, they were within the interdural compartment and were not extending within the spinal dural tube. Although type B and C tumors were located outside the spinal dural tube, they had a dural or perineural sheath cover that was an extension of the spinal dura. This dural sheath was well defined and formed a firm limiting membrane that separated the tumor from the adjoining structures of the region. The dura was not transgressed by these tumors, and the vertebral artery and adjoining venous plexuses were displaced by the tumor mass. Although there was no pure type C tumor, inclusion of this group into the classification scheme assisted in categorization of the tumor regarding its physical size and nature and indicated the extent of surgical complexities. Infiltration of paraspinal muscles is rare and suggestive of malignant change and was not encountered.