Under the title “Subacute Necrotic Myelitis,” Foix and Alajouanine, and later Greenfield and Turner, and subsequently, Hughes, described a disorder mainly of adult men characterized by amyotrophic paraplegia that ran a progressive course over several months. The defining feature, one that still gives rise to lively polemical discussions, is severe necrosis of both gray and white matter in the lumbosacral region and a marked increase in the number of small vessels, their walls thickened, cellular, and fibrotic (“angiodysplastic”), yet without vascular occlusion. The veins are also thickened and surrounded by lymphocytes, mononuclear cells, and macrophages. As such, the disorder could be included under the vascular myelopathies discussed in the next section.
These findings have been difficult to interpret and their relationship to the group of arteriovenous malformations and fistulas, discussed later, has been unclear but we are inclined to the view of Antoni and others who were impressed with the prominence of large arteries and veins and have reinterpreted this pathologic process as an arteriovenous malformation. In many other cases of necrotic myelopathy that are not associated with a true vascular malformation, the vascular changes simply reflect a neovascular response to necrosis or may be examples of neuromyelitis optica.
A similar syndrome is produced by a rare idiopathic necrotizing vasculitis that is confined to the spinal cord (Caccamo et al). In these cases, there is a persistent and marked pleocytosis and some clinical stabilization with corticosteroids. One of our young male patients with this type of subacute necrotizing myelitis, responsive to corticosteroids, had mononuclear cells in the spinal fluid persistently over a year and died as a result of fulminant inflammatory cerebral hemorrhages. There were multiple occlusions of small vessels surrounding the spinal cord and a vasculitis. Polyarteritis nodosa and necrotizing arteritis only rarely involve the spinal cord. Schistosomiasis, as mentioned earlier, may also produce a necrotizing myelitis of the lumbosacral region.
This is an interesting and varied group of spinal cord disorders that are thought to be inflammatory but their nature has not been fully elucidated to our satisfaction in part because of a paucity of pathologic material. An inflammatory vasculopathy has been implicated, similar to what is imputed for cerebral lesions, but there may be areas of noninflammatory and nonvasculitic demyelination that simulate multiple sclerosis. The imaging features and response to treatment are likewise varied.
A rapidly evolving or subacute myelopathy occurs in association with systemic lupus erythematosus. As mentioned, the process is presumed to arise from a microvasculitis or an autoantibody. Propper and Bucknall presented such a case and reviewed 44 others in which patients with lupus developed a transverse myelitis over a period of days. There was back pain at the level of sensory loss (the cases we have seen have been painless), and pleocytosis and elevation of CSF protein. The MRI revealed segmental swelling of the spinal cord. Postmortem examinations have disclosed widespread vasculopathy of small vessels with variable inflammation and myelomalacia, and, rarely, a vacuolar myelopathy. Whether demyelination (so-called lupoid sclerosis due to an antibody reaction) can occur independently of a vasculopathy has not been clear to the authors.
Some but not all cases also have circulating antiphospholipid antibody; the relationship of these antibodies to the myelopathy and to microvascular occlusion is uncertain (see also “Antiphospholipid Antibody Syndrome” in Chap. 33 and further discussion in Chap. 35). The incidence of lupus myelopathy is not known; it must be rare but one such case is admitted to our service, in a hospital with an active rheumatology division, about every year.