This article includes discussion of transverse myelitis, acute myelomalacia, acute spontaneous myelitis, ascending myelitis, ascending transverse myelitis, myelomalacia, and transverse myelopathy. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.
Transverse myelitis is part of a spectrum of demyelinating disease but has unique features that differentiate it from multiple sclerosis. In this updated article, the author describes new developments in the diagnosis of subgroups of myelitis caused by neuromyelitis optica and cord involvement from CNS Sjögren disease.
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• Acute transverse myelitis, as defined here, is idiopathic and excludes other forms of myelitis (neuromyelitis optica, postinfectious and postvaccinal myelitis, multiple sclerosis, etc.).
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• Cord symptoms evolve over hours to days and then typically resolve over several weeks or months.
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• The pathology is similar to multiple sclerosis, but only 40% will develop multiple sclerosis.
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• Cord lesions in neuromyelitis optica (NMO, Devic disease) and CNS Sjögren disease are longitudinal, down the center of the cord; in multiple sclerosis the lesions are shorter and acentric.
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• High-dose glucocorticosteroids hasten recovery but have no long-term benefit.
Historical note and terminology
Transverse lesions of the spinal cord were ascribed to thrombosis that was caused by arteriosclerosis, syphilis, and other infections by Bastian in the 1880s (48), and this concept persisted well into the next century. Foix and Alajouanine also believed that transverse myelitis had a vascular etiology (47). They described 2 patients with subacute necrosis in the sacral or thoracolumbosacral cord associated with massive dilatation and endomysial hypertrophy of the extramedullary veins and similar but less marked changes in the intramedullary vessels. The lumens were not obliterated, and the arteries were not involved. The term "angiodysgenetic necrotizing myelopathy" is sometimes applied to this condition (48). A similar syndrome is believed to be caused by spinal dural arteriovenous fistulae, although Mirich and colleagues found no arteriovenous malformations in 4 typical cases of subacute necrotizing myelopathy (110). Paine and Byers were the first to report a large clinical series with follow-up exams and used the term “transverse myelopathy” (123). They also postulated a vascular cause but did not present any pathological evidence. In most of these early reports, 1 or 2 patients were studied, and the autopsies were performed months to years after the original illness (72).
Autopsies from patients with acute transverse myelitis seldom show significant vascular alterations. Lipton's series of 34 contained only 2 cases with infarcts of unknown etiology and one with hemorrhage plus telangiectasias (102).
Other investigators assumed the condition was an inflammatory myelitis from an antigen-antibody reaction (131) or a hypersensitivity reaction to infection or vaccination (114). Histology showed demyelination, variable destruction of axons, and differing degrees of mononuclear cell infiltration. (There was loss of myelin in the cases of Foix and Alajouanine, but this does not prove that demyelination was the primary event.)
Several large series appeared in the 1960s and 1970s (04; 102; 139; 20). A consensus evolved that acute transverse myelitis was an inflammatory demyelinating disease of the cord. It sometimes followed infections, but usually had no antecedent. In a series of 33 cases of acute or subacute noncompressive myelopathy, 46% were parainfectious, 12% were associated with cord ischemia, 21% were multiple sclerosis exacerbations, and 21% were idiopathic (75). The underlying infection is seldom diagnosed.
Many types of cord lesion or systemic disease can cause a transverse spinal cord syndrome or myelopathy. Etiologies are infectious, neoplastic, compressive, traumatic, embolic, degenerative, or vitamin-substrate deficiency. However, acute transverse myelitis, as defined here, is an idiopathic disorder caused by inflammation of the spinal cord, associated with marked demyelination and often with significant axonal loss. The process that instigates the inflammation in transverse myelitis is unknown. (This includes the third of transverse myelitis patients with antecedent virus infections.)
Specific diagnostic criteria for transverse myelitis have been proposed (Group TMCW 2002). These include (1) neurologic symptoms attributable solely to the spinal cord, ie, negative brain MRI and no clinical brain symptoms, (2) bilateral signs or symptoms, (3) clearly defined sensory level, (4) MRI exclusion of compression, (5) inflammation in the spinal cord (CSF cells or IgG index, or MRI gadolinium enhancement) seen at onset or within 7 days, (6) progressive worsening with maxima from 4 hours to 21 days after onset, and (7) no other etiology. With these strict criteria, only 16% of 288 patients with acute transverse myelitis from all causes have idiopathic acute transverse myelitis (38). Scott and colleagues argue that inflammation is less common in transverse myelitis than in multiple sclerosis and thus, inflammation should not be used as a criterion (149). Acute transverse myelitis can be split into complete or partial transverse myelitis, each with a different outcome (146).
These definitions are undergoing revision. A subset of transverse myelitis is associated with antibodies against aquaporin-4 (“NMO-IgG”, ie, neuromyelitis optica [NMO], Devic disease), and another partially overlapping subgroup is associated with Sjögren disease (73). These differ markedly from multiple sclerosis. Unfortunately, many of the classic treatises on idiopathic transverse myelitis include some of these patients.
In the following discussion, idiopathic transverse myelitis is assumed to be part of the multiple sclerosis spectrum of demyelination.