Necrotizing myelopathy.

The preceding paper by Mirich et al. [1] describes the MR findings in four subjects with biopsy-proved necrotizing myelopathy. In the first three patients, the clinical course was characterized by progressive motor and sensory dysfunction in the lower extremities, evolving over periods ranging from 3 months to 2 years. In the fourth case, the clinical course was characterized by a Brown-Sequard syndrome with a C4 sensory level that developed over a 3-week period. All four patients had abrupt worsening of their signs and symptoms. In each instance, initial MR imaging showed focal intramedullary expansion of the spinal cord, and histologic examination of the specimen obtained at surgery showed parenchymal coagulative necrosis and thickening and hyalinization of the vascular walls . A definite etiologic diagnosis could not be made. The development of clinically progressive necrosis of the spinal cord not related to traumatic injury, an infectious or a primary inflammatory process, or infiltration or compression by neoplasm, though not particularly common, may pose difficulties in diagnosis. The purpose of this discussion is to review briefly some of the disorders that might be considered. Among the circulatory disorders, the most frequently discussed are those that are related to impairment of spinal venous outflow. Clinically, nonhemorrhagic venous infarction of the spinal cord tends to evolve over a period of weeks to months and is typically accompanied by extensive thrombosis within leptomeningeal veins [2] . The longitudinal extent of the damage is variable but may be considerable. Factors that predispose its development include hypercoagulability (e.g., migratory thrombophlebitis or polycythemia rubra vera) or spinal venous hypertension (such as that seen in the presence