[A case of brain dead patient with a spinal pathology of preserved marginal white matter and pencil-shaped softening--a theory for pathogenesis of pencil-shaped softening].

We reported a case of brain death which had been caused by massive cerebral hemorrhage. The spinal pathology showed preserved marginal parts of spinal white matter in the segments of C7 to T5 and S1 to S3, and the other parts showed necrosis. We found pencil-shaped softening (PS)-like lesion in the segment C8 to T2, but the lesion was more preserved than the surrounding tissue. The intraspinal structure of C5 was distorted by the necrotic cerebellar tissue in the subarachnoid space of the segment and the posterior column area was decreased. The posterior column in C5 and PS showed the same severe pathology. Because the pia mater of the spinal cord is not so easily torn, and has some elasticity, swollen spinal necrotic tissue has no place to move but in a longitudinal direction; that circumstance may cause the PS. In this case the subarachnoid cerebellar tissue restricted the expansion of the spinal cord in C5, which might have helped cause PS. So we suggest that the subarachnoidal cerebellar tissue and changes of antero-posterior diameter in the spinal column, when the spine is flexed or extended, may contribute to the pathogenesis of PS. In this case the pathology of the PS was reversed as compared to the usual PS, because the PS was relatively preserved while the surrounding tissue was necrotic. There have been only a few reports which show preserved marginal white matter of the spinal cord.(ABSTRACT TRUNCATED AT 250 WORDS)