Myelitis is infection or inflammation of myelin (the lipoid membrane covering nerve fibers) sensu stricto of the spinal cord resulting, as it were, in disruption of transmission of nerve impulses between the spinal cord and the rest of the body. The signs and symptoms of myelitis depend upon the cause and location of the lesions.
The signs and symptoms of myelitis are determined by the causative agent (infectious or immune-mediated), location of the lesions and associated disease(s).
These are (in alphabetical order):
The onset of symptoms in transverse myelitis (TM) is characterized by sudden neck and back pain, with loss of bladder or bowel control. Sharp pains are common. Poliomyelitis is accompanied by fever, headache, nausea, fatigue, stiffness and pain in the neck, back and extremities.
The duration of illness in TM is from a few hours to several days (acute) or more than 1 to 4 weeks (subacute). Chief complains include localized lower back pain, paresthesias (abnormal sensations of tickling, burning, pricking, or tingling) in the legs, loss of sensorium, and paraparesis. At a later stage, paraplegia may ensue, with urinary bladder and bowel dysfunctions. Some patients may experience muscle spasms, discomfort, headache, fever, anorexia and respiratory problems depending on the location of lesions in the spinal cord.
Diagnosis of TM:
In the absence of an identifiable etiologic agent the condition is diagnosed to be idiopathic transverse myelitis (IATM).
Early diagnosis and treatment is important. Given the varied nature of myelitis, only after thorough consideration of probable cause and clinical course of each type of myelitis, may one prescribe the following modes of treatment:
Recovery from transverse myelitis is expected within 2 to 12 weeks after the onset of symptoms, or longer; it may extend up to 2 years and beyond in some cases. Otherwise the likelihood for complete recovery is nil without evident clinical improvement within 3 to 6 months. Partial recovery, if at all, may be expected with aggressive physical therapy and rehabilitation.
In retrospect, with conservative therapy, one third of patients recover sufficiently as to be able to resume certain activities normally such as walking, with improved urinary and bowel functions and minimal paresthesia. A third group may recover partially with residual deficits such as spastic gait, sensory dysfunction, and urinary urgency or incontinence. Refractory patients may remain bedridden or wheelchair-bound and unable to perform normal daily functions. It has been shown that prognosis is poor with rapid onset of symptoms. Nonetheless, radical therapy and long-term rehabilitation should be undertaken.
Causes of myelitis:
In the USA less than 200,000 people are affected by myelitis, hence, it is listed as a "rare disease" by the Office of Rare Diseases (ORD) of the National Institutes of Health. However, this is not the case particularly in the tropics where infectious diseases are highly prevalent.
A nationwide outbreak of acute myelitis in children has been reported in the literature . Transverse myelitis (TM) affects all persons regardless of age, gender, ethnic origin; evidently, with no hereditary predisposition. New cases are seen each year in the high risk groups of 10 to 19 years and 30 to 39 years. The annual incidence of TM in the U.S. is around 1,400; 33,000 Americans have some kind of disability that is associated with TM. Acute transverse myelitis (ATM) is either idiopathic, i.e., of unknown etiology (IATM) or secondary, i.e., associated with a known cause or condition (SATM). IATM is an immune-mediated demyelinating inflammation of the spinal cord. The annual incidence of IATM is estimated between 1 in 1,000,000 and 1 in 250,000 population.
SATM is linked to an infectious disease entity or an autoimmune condition. Other parts of the nervous system may be involved thus, the optic nerves in multiple sclerosis (MS) and neuromyelitis optica (NMO) or Devic's disease, the peripheral nerves in systemic lupus erythematosus (SLE) or anti-Ro/SS-A antibodies in Sjogren's syndrome. Direct attack or invasion of the spinal cord by parasites and microbial pathogens can likewise cause SATM. The incidence of SATM depends on a multiplicity of causes hence it is difficult to come up with a composite estimate.
The histopathology of acute transverse myelitis (ATM) is confined to the spinal cord. For example, the histology differs from multiple sclerosis. In MS, axons are usually intact and lesions are few and scattered (primary demyelination) whereas in ATM there is extensive demyelination and damage to axons; lesions may be cavitary in severe transverse myelitis.
Necrotizing processes are involved in addition to inflammation and demyelination as in Devic's disease, acute hemorrhagic leukoencephalitis and progressive necrotizing myelopathy. These diseases differ in their clinical course, histology, serum marker and nature of the lesions. Neuromyelitis optica (NMO), or Devic's disease, is characterized by an immune attack on the optic nerve and spinal cord. Serological tests in 70% of patients with NMO have an IgG antibody called aquaporin-4 (AQP4). In both Devic's disease and TM, lesions are located in the center of the cord with intact sections in subpial areas. Cerebrospinal fluid (CSF) shows elevated protein with transient or absent oligoclonal bands. The spinal cord is swollen in MRI. In a study, antibodies against myelin-associated glycoprotein were found in all cases of Devic's disease . The finding of aquaporin 4 in NMO differentiates cases of optic neuritis and myelitis from multiple sclerosis, heretofore, necessitating a different therapeutic approach .
Inflammatory cytokines e.g., IL-6 is increased in CSF in MS and inflammatory neurologic diseases. The elevation can reach 300-fold in cases of idiopathic transverse myelitis versus non-IAMT .
When the prospect of clinical cure appear to outweigh the associated risk of neurological problems arising after vaccination, which is considered very low, the choice of preventive measure should be based on that premise.