Management Of Extradural Spinal Tumors

characterizes the lesion. The treatment is excision. Instrumentation and fusion may be required if there is severe scoliosis, although minor deformities will resolve with resection alone. Overall, there is an excellent prognosis, with marginal recurrence rates related to inadequate excision of the nidus [1-4,6].

Osteoblastomas differ from osteoid osteomas in their attaining greater size (more than 2 cm). Histologically, the two lesions cannot be differentiated. Less common than osteoid osteomas, osteoblastomas represent less than 2% of primary benign bone tumors, but have a greater propensity for axial skeletal involvement. Approximately 30-40% of osteoblas-tomas involve the axial skeleton. The lesions are distributed throughout the longitudinal axis of the spine, occur most commonly in the posterior elements and have a propensity to produce spinal deformity (Fig. 30.1). In 90% of cases, osteoblastomas present in patients of 30 years of age or younger; these lesions have a male to female predominance of 2:1. Clinical presentation characteristically involves a higher incidence of neurological deficit, secondary to lesion size. Treatment is en-bloc resection, usually with resolution of scoliotic deformity. Prognosis is favorable with adequate removal. Long-term recurrence rates approach 10% [1-4,6].

Giant cell tumors (GCTs) are benign lesions of unknown cell origin. These aggressive tumors

Fig. 30.1. Axial CT scan of an osteoblastoma. The patient is an 11-year-old male with a 6-month history of progressive neck pain.

carry some malignant potential and a high incidence of local recurrence. They are responsible for 21% of all primary benign bone tumors and affect the spinal axis in 8-11% of all cases. They most commonly occur in the sacral region, when the spinal column is involved. Unlike the majority of primary bone tumors, GCTs are generally found in individuals in the third and fourth decades of life, with decreasing frequency in later years. Women are affected slightly more commonly than are men. Plain radiographs demonstrate cortical expansion, with little reactive sclerosis or periosteal reaction. MR images reveal homogeneous signals, while CT studies can better delineate the degree of vertebral bone involvement and define surgical margins. Because of the non-distinct histological characteristics of GCTs, a thorough evaluation, including radiographic investigation coupled with histopathology, is important, to differentiate this condition from other primary bone tumors. Treatment is usually an aggressive en-bloc resection, with consideration of adjuvant radiation therapy. There is a relatively poor prognosis because of the high recurrence rates (50%). These tumors have the potential for malignant transformation, especially after local radiation if surgical margins were inadequate [1-4].

Aneurysmal bone cysts (ABCs) are benign, non-neoplastic proliferative lesions. Although only responsible for approximately 1-2% of all primary bone tumors, ABCs affect the axial skeleton in 12-25% of all reported cases. The pathogenesis is unclear, but accepted theories include an underlying tumor or traumatic arteriovenous malformation, with subsequent development of a cyst. Histologically, ABCs contain fluid-filled spaces, separated by fibrous septa. The incidence of ABCs is greater in the thoracolumbar region. As in the majority of benign osseous lesions, posterior location predominates, with 60% of spinal aneurysmal bone cysts occurring in the posterior elements. ABCs typically present in young patients who are in their second decade of life, with a slight predominance in women. Radiographic imaging with MRI and CT demonstrates a multilocu-lated, expansile, highly vascular osteolytic lesion with a thin, well demarcated, eggshell-like cortical rim (Fig. 30.2). Multiple-level vertebral involvement may occur in up to 40% of cases. Treatment involves pre-operative embolization and surgical resection, or embolization alone

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