Spinal pencil-shaped softening. Report of an autopsy case studied using a three-dimensional model

The pathologic features of a case of spinal pencil-shaped softening (PS) were studied by detailed step-sectioning and reconstruction using a three-dimensional (3D) model. The spinal cord was obtained at autopsy from a patient who had developed paraplegia due to extradural involvement of lung cancer. Above and below the area of transverse necrosis were PSs containing necrotic debris. They compressed the surrounding tissue and extended longitudinally over several segments. The PS was continuous with the area of transverse necrosis. These findings support the hypothesis that PS is formed by penetration of necrotic debris. The 3D model revealed that the PS was cylindrical to spindle-shaped. It showed a remarkable change in width along its course, with an unusual expanding shape. The PS was mainly located in the ventral part of the posterior column but was also observed in other locations in the segment near the transverse necrosis. Detailed step-sectioning showed that the PS changed in width mainly in response to intrapial pressure, and that it occurred where the parenchymal tissue was fragile. The expansion produced by penetration of necrotic debris may thus play an important role in the morphogenesis of this unusual lesion. Furthermore, the condition of the surrounding tissue may also be an important factor influencing the width and location of PS.