Intradural Spine Tumors

Intradural spinal cord tumors have a prevalence of 3-10/100000 per year. They predominantly occur in the middle-aged group. The most common tumors are nerve sheath tumors which account for about 30%, and meningiomas, which account for another 25%. The remainder include intramedullary tumors. The most common intramedullary tumors are astrocytomas and ependymomas. Hemangioblastomas, cavernomas, dermoids, epidermoids and lipomas and others are even more uncommon.

Since the majority of these tumors are benign and slow growing there is often an indolent clinical course. Pain along the spinal axis is the most common complaint often persisting for several years before it leads to evaluation and imaging workup. Sixty to 70 % of the adult patients have pain as their initial symptom.

The pain is described differently in extra- vs. intramedullary lesions: extramedullary tumors are eccentric in location and thus produce mostly unilateral, segmentally distributed pain. Intramedullary tumors more frequently cause diffuse dysesthetic pain, that is most pronounced during the early morning hours.

Motor and sensory deficits produced by extramedullary tumors are often segmental or unilateral, not infrequently of a Brown-Sequard type, while in intramedullary tumors they are usually diffuse.

Tumors involving the conus or the cauda equina may selectively impair sphincter control and sexual function, and these symptoms may precede other neurologic signs for months or even years. This may be misdiagnosed for some sort of "functional" entity before imaging reveals the true nature of the lesion.

The extent of tumor growth and neurologic involvement depends upon the location of the tumor within the spinal canal. Lesions in the upper cervical spine tend to involve the upper extremities. Involvement of the thoracic region evokes sensory and motor changes in the abdomen or lower extremities.

Pathology

Extramedullary Tumors

Nerve sheath tumors usually arise from the dorsal roots. These tumors are relatively avascular, globoid and without calcification. The dorsal root is intimately involved in the tumor and can rarely be preserved during surgical resection. When these tumors have a dumbbell configuration the size of the extradural component may exceed the intradural component.

Meningiomas, unlike nerve sheath tumors, arise from arachnoid cluster cells and thus can be separated from the nerve roots. These tumors tend to have a lateral or ventrolateral relationship to the spinal cord. They may arise in any age group, mostly occurring between the 5th and 7th decade of life, and tend to have a female preponderance. The thoracic region accounts for 80% of these tumors.

Intramedullary Tumors

Astrocytomas are the most common intramedullary tumor. They occur at any age but are most frequent in the first three decades. The majority of these neoplasms are benign. They vary in appearance and are not well demarcated from the surrounding neural tissue. Cysts lined by non-neoplastic tissue frequently accompany these tumors.

Gangliogliomas are benign neoplasms, common in children and young adults. They consist of well-differentiated neoplastic neurons and astrocytes. The neurons are readily recognized by their characteristic nuclear and nucleolar features, abundance of cytoplasm, content of Nissl substance, and the presence of argyrophilic neuritic processes. Their expression of neuronal markers like synaptophysin and neurofilament proteins also serve to identify these abnormal neurons. Most gangliogliomas grow slowly and have an indolent course.

Ependymomas are the most common intramedullary neoplasm in adults, while in children they account for only 10% of all intramedullary tumors. These tumors typically have a central location in the spinal cord. They occur throughout the spinal axis. At surgery ependymomas appear reddish gray with variable blood supply which always comes from the anterior spinal artery. They are well delineated from the surrounding spinal cord and have rostral and caudal cysts which cap the tumor poles. They are histologically benign.

Hemangioblastomas account for 3 to 7% of all intramedullary spinal cord tumors and are particularly rare in children. They occur throughout the spinal canal. Spinal hemangioblastomas are mostly sporadic, but up to 25% of patients will have von Hippel-Lindau disease.