Case of the Week

Background:

• Previously known as spinal paragangliomas, these are molecularly and genetically distinct and have been redefined in the 5th edition of the WHO Classification of CNS Tumors as neuroendocrine tumor, WHO grade 1.
• Neuroendocrine tumors are derived from enterochromaffin cells and usually originate in the gastrointestinal tract or lungs. Most behave in a benign fashion, but they can be aggressive and metastasize, including to the CNS.
• Primary CNS neuroendocrine tumors are extremely rare and almost always sporadic. They may secrete neuropeptides such as 5-hydroxytryptamine and somatostatin, but generally do not produce symptoms related to chemical secretion.

Clinical Presentation:

• Symptoms are varied and include lower back pain and sciatica. Patients with larger tumors can present with symptoms related to spinal cord compression and cauda equina syndrome with bladder and bowel dysfunction.
• Patients with associated superficial siderosis may present with slowly progressive gait ataxia with cerebellar dysarthria, sensorineural hearing impairment, and headache. 

Key Diagnostic Features:

• MRI shows an avidly enhancing and well-circumscribed intradural-extramedullary tumor. Lesions grow slowly and may result in scalloping of the vertebral bodies. Tumors are soft and tend to grow along the axis of the spinal canal resulting in a tubular or “sausage” shape, similar to myxopapillary ependymomas. They are hypo- or isointense on T1-weighted images and hyperintense on T2-weighted images. Hemorrhage and cystic degeneration are common, which may lead to a hemosiderin cap sign and a complex solid-cystic appearance.
• Associated syringohydromyelia and the characteristic salt-and-pepper appearance of paragangliomas can be seen in rare cases.
• Neuroendocrine tumors are highly vascular and commonly have intra- and/or peritumoral serpentine flow voids that are best seen on T2-weighted images. They can present with extensive venous engorgement along the spinal cord as seen in our case.

Differential Diagnoses:

• Spinal neuroendocrine tumors are rare and require histology for definitive diagnosis. The differential diagnosis is essentially that of other intradural extramedullary tumors, particularly those located in the lumbar region.
• Myxopapillary ependymoma: These are usually located at the filum terminale and/or conus medullaris and can be indistinguishable from neuroendocrine tumors. They are frequently hyperintense on T2WI due to mucinous content and may be calcified. Enhancement is generally homogeneous except when there is associated intratumoral hemorrhage or cystic degeneration. These slow-growing tumors may expand the spinal canal, cause scalloping of the vertebral bodies and may extend out of the neural foramina.
• Hemangioblastoma: Most are sporadic and only one-third are associated with Von Hippel-Lindau syndrome. Hemangioblastomas are usually intramedullary with eccentric exophytic components and a minority are extramedullary or extradural. Tumors are hyperintense on T2WI and may have a hemosiderin cap. The mural nodule shows intense and homogeneous enhancement, and a cystic component and/or syrinx is common. Dilated arteries and prominent draining veins with serpentine flow voids are also characteristic of hemangioblastomas.
• Intradural nerve sheath tumors: Schwannomas and neurofibromas are well-circumscribed, round or lobulated, and generally solid T2-hyperintense masses with moderate postcontrast enhancement. As opposed to neuroendocrine tumors, nerve sheath tumors do not show such prominent and extensive vascularity. However, schwannomas may demonstrate intratumoral hemorrhage, cystic degeneration, and rarely fatty degeneration, which may resemble the complex cystic and solid appearance of the spinal neuroendocrine tumors.
• Spinal meningioma: Very rare in the lumbar region, only 5% of all spinal meningiomas arise from this site. These are iso- to slightly hyperintense on T2WI, have a broad-based dural attachment, and may show a dural tail sign that enhances more avidly than the tumor. On CT, meningiomas may demonstrate an iso- to slightly hyperdense appearance, sometimes with partial or dense calcification. Adjacent hyperostosis is usually absent in spinal meningiomas.

Treatment:

• Surgical resection is the treatment of choice, though some cases may require preoperative embolization to decrease the risk of significant blood loss during surgery. Complete surgical resection is generally curative for spinal neuroendocrine tumors. In case of incomplete resection, radiotherapy can be a successful complementary treatment option. The recurrence rate is less than 5% after complete resection.
• Strict and prolonged postoperative follow-up is crucial due to the late relapse of some tumors after resection.
• Our patient underwent T11–L3 laminectomy for complete resection of the intradural tumor with T11–L4 instrumented fusion for stabilization. At around 6 weeks of follow-up, his mobility continues to improve.