Spinal cord astrocytomas are quite uncommon and account for only 3% to 4% of all central nervous system (CNS) astrocytomas. Furthermore, although intracranial glioblastomas are the most common primary brain parenchymal neoplasm, spinal cord glioblastomas are exceedingly rare.

The characteristic asymmetric location of small spinal cord astrocytomas is due to the location of their peripherally located astrocytic cells of origin, as well as their affinity to grow along the spinal cord white matter tracts. Both on gross inspection and imaging evaluation, astrocytomas tend to be poorly defined with infiltration beyond the visible margins ( Figs. 34.1 and 34.2 ).

Figure 34.1, Axial and coronal illustrations of a cervical spinal cord astrocytoma. A heterogenous intramedullary mass is evident. A rostral cystic component can be seen on coronal view. Note the characteristic peripheral location and ill-defined margins of the lesion, indicative of its infiltrative growth pattern.

Figure 34.2, Eccentric exophytic infiltrative astrocytoma. A coronal T2 image (A) of the cervical spine demonstrates the classic appearance of an intramedullary astrocytoma with a heterogenous eccentric lesion along the left side of the spinal cord (red arrow) . Axial T2 (B) and axial T1 postcontrast (C) images through the lesion demonstrate a T2 hyperintense lesion with ill-defined borders (blue arrows) with an enhancing exophytic component extending beyond the normal margins of the cord (green arrow) . Notice the area of more infiltrative appearing enhancement posteriorly (orange arrow) .

At the time of diagnosis many of these lesions are often quite extensive, on average covering five vertebral segments. These infiltrating astrocytomas therefore appear as expansile, T1 isointense/hypointense and T2 hyperintense lesions often spanning multiple levels ( Fig. 34.3 ). An association with NF-1 exists.

Figure 34.3, Infiltrative astrocytoma. Middle-aged female presenting with slowly progressive Brown-Séquard syndrome along with T8 sensory loss. Sagittal T2 (A) image of the thoracic spinal cord reveals a multifocal lesion. Superiorly, a large expansile mass is evident ( yellow arrow and axial T2 image [a1]). The lesion extends inferiorly as a peripheral ill-defined area of T2 hyperintensity ( blue arrow and axial T2 image [a2]). A second peripheral and slightly exophytic component is evident inferior to this level ( red arrow and axial T2 image [a3]). Sagittal T1 (B) and sagittal T1 fat-saturated postcontrast (C) images demonstrate mild patchy enhancement associated with a1 (yellow bracket) , and no appreciable enhancement associated with the components at a2 (blue bracket) or a3 (red bracket) . The infiltrative ill-defined appearance, mild patchy enhancement and nonenhancing portions all point to the diagnosis of infiltrative astrocytoma.

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