Lower cranial nerve schwannomas are rare and when present are located in the jugular foramen most commonly arise from the glossopharyngeal or vagal nerves with accessory nerve involvement being least common. The other locations in the accessory nerve course where schwannomas arise are extracranial beyond the jugular foramen in the cervical region and cisternal proximal to the jugular foramen. Both of these are very rare locations 1).
Till 2013, a total of 28 cases of spinal accessory nerve schwannomas have been reported, among which four were reported in the craniocervical region, which extended from C1 or C2 to the vermis, with only three being located in the cervical region 2).
Julow presented two cases of accessory nerve schwannomas and suggested that they could be divided into two groups, namely, intrajugular schwannomas that grow into the cisterna magna and intracisternal accessory nerve schwannoma that grow into the jugular foramen 3).
Patients with intrajugular schwannomas usually present with a jugular foramen syndrome because the tumor is confined entirely within the foramen. Radiological diagnosis of jugular foramen tumors using CT or conventional x-rays is often difficult 5).
Patients with intracisternal accessory nerve schwannoma usually have an accessory nerve palsy, cerebellar syndrome, and/or myelopathy. Deficits of glossopharyngeal or vagal function have not been reported 6).
Imaging studies help in the accurate diagnosis of schwannomas, with a reasonably good accuracy.
In some cases enlargement of the jugular foramen is evident on CT and this is a valuable diagnostic feature. MR has made diagnosis much easier even though it is still not possible to identify the nerve of origin 7) 8).
They usually have regular contours and a round or oval shape, lack edema, and enhance homogenously with contrast. Cystic degeneration is generally seen in large tumors and this may alter the otherwise uniform texture of the mass. 9).
MRI scans are very helpful in identifying the tumours and their correlations with the surrounding vascular structures, muscles, and nerves 12).
This imaging provides information on the tumour size, location, extent and the surrounding anatomy, and it enables the surgical planning 13).
A gross total resection remains the treatment of choice for these tumours, because they are radio resistant.
The other treatment option is sterotactic radiosurgery (SRS). SRS is gaining popularity, but it depends on many factors, which include the size and the location of the Schwanoma and the age of the patient. Whenever it is possible, SRS should be avoided in young patients Jayaraman M, Smirniotopoulos JG, Davis LM, Patel MR, Krasny RM. Imaging in cranial nerve schwannoma. Available at url. http://emedicine.medscape.com/article/336141-overview (Accessed on 4 April, 2019)
Postoperative accessory nerve deficits also seem to depend on the degree of damage to the nerve. In the case reported by Caputi and colleagues, dissection was performed along the arachnoid interface, exposing the tumor attachment to the spinal accessory nerve, from which it was removed en bloc with no apparent damage caused to the nerve 14).
Their patient recovered completely without any impairment of neck movement. However, in another case in which the fibers of the accessory nerve entered the tumor and were coagulated and cut, the patient experienced shoulder muscle weakness and impairment of neck motion postoperatively 15).
So, in cases where the mass originates from a spinal accessory rootlet, the damage to the rootlet does not lead to the development of specific accessory nerve signs 16).
In the case of Juang et al., a spinal accessory rootlet near the spinal cord was the place of origin of the tumor and resulted in a lack of postoperative symptoms and signs 17).
Total removal of these tumors is recommended as recurrence is probably unavoidable if removal is incomplete 18).