Myelitis
Myelitis involves the infection or the inflammation of white matter or gray matter of spinal cord which is a part of central nervous system that acts as a bridge between a brain and the rest of a body. During an inflammatory response on the spinal cord, the myelination and axon may be damaged causing symptoms such as paralysis and sensory loss. Myelitis is classified to several categories depending on the area or the cause of the lesion; however, people often refer to any inflammatory attack on the spinal cord as transverse myelitis.
Etiology
Many so-called “causes” remain unproven. Immunologic response against the CNS (most likely via cell-mediated component) is the probable common mechanism. Animal model: experimental allergic encephalomyelitis (requires myelin basic protein of CNS, not peripheral). Generally accepted etiologies include (items with an asterisk * may be more properly associated with myelopathy rather than myelitis): 1. infectious and post-infectious
a) primary infectious myelitis
● viral: poliomyelitis, myelitis with viral encephalomyelitis, herpes zoster, rabies
● bacterial: including tuberculoma of spinal cord
● spirochetal: AKA syphilitic myelitis. Causes syphilitic endarteritis
● fungal (aspergillosis, blastomycosis, cryptococcosis)
● parasitic (Echinococcus, cysticercosis, paragonimiasis, schistosomiasis)
b) post-infectious:includingpost-exanthematous,influenza
2. posttraumatic
3. physical agents
a) decompression sickness(dysbarism)
b) electrical injury*
c) post-irradiation
4. paraneoplastic syndrome (remote effect of cancer): most common primary is lung, but prostate, ovary and rectum have also been described
5. metabolic
b) pernicious anemia*
c) chronic liver disease*
6. toxins
a) cresyl phosphate*
b) intra-arterial contrast agents*
c) spinal anesthetics
d) myelographic contrast agents
e) following chemonucleolysis
7. arachnoiditis
8. autoimmune
a) multiple sclerosis(MS), especially Devic syndrome
b) following vaccination(smallpox,rabies)
9. collagen vascular disease
a) systemic lupus erythematosus
b) mixed connective tissue disease