Transverse myelitis

Transverse myelitis is a neurologic disorder caused by a loss of the myelin encasing the spinal cord, also known as demyelination. This demyelination arises idiopathically following infections or vaccination, or due to multiple sclerosis. One major theory of the cause is that an immune-mediated inflammation is present as the result of exposure to a viral antigen.

The lesions are inflammatory, and involve the spinal cord on both sides. With acute transverse myelitis, the onset is sudden and progresses rapidly in hours and days. The lesions can be present anywhere in the spinal cord, though it is usually restricted to only a small portion.

In some cases, the disease is presumedly caused by viral infections or vaccinations and has also been associated with spinal cord injuries, immune reactions, schistosomiasis and insufficient blood flow through spinal cord vessels. Symptoms include weakness and numbness of the limbs as well as motor, sensory, and sphincter deficits. Severe backpain may occur in some patients at the onset of the disease. Treatment is usually symptomatic only, corticosteroids being used with limited success. A major differentiation or distinction to be made is a similar condition due to compression of the spinal cord in the spinal canal, due to disease of the surrounding vertebral column.

Prognosis for complete recovery is generally poor. Recovery from transverse myelitis usually begins between weeks 2 and 12 following onset and may continue for up to 2 years in some patients, many of whom are left with considerable disabilities. Some patients show no signs of recovery whatsoever.

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The symptoms and signs depend upon the level of the spinal cord involved and the extent of the involvement of the various long tracts. In some cases, there is almost total paralysis and sensory loss below the level of the lesion. In other cases, such loss is only partial. If the high cervical area is involved, all four limbs may be involved and there is risk of respiratory paralysis (segments C3,4,5 to diaphragm). Lesions of the lower cervical (C2-T1) region will cause a combination of upper and lower motor neuron signs in the upper limbs, and exclusively upper motor neuron signs in the lower limbs. A lesion of the thoracic spinal cord (T1-12) will produce a spastic paraplegia. A lesion of the lower part of the spinal cord (L1-S5) often produces a combination of upper and lower motor neuron signs in the lower limbs. The degree and type of sensory loss will depend upon the extent of the involvement of the various sensory tracts, but there is often a "sensory level" (at the sensory segmental level of the spinal cord below which sensation to pin or light touch is impaired). This has proven to be a reasonably reliable sign of the level of the lesion. Bladder paralysis often occurs and urinary retention is an early manifestation. Considerable pain often occurs in the back, extending laterally to involve the sensory distribution of the diseased spinal segments--so-called "radicular pain." Thus, a lesion at the T8 level will produce pain radiating from the spine laterally along the lower costal margins. These signs and symptoms may progress to severe weakness within hours. (Because of the acuteness of this lesion, signs of spinal shock may be evident, in which the lower limbs will be flaccid and areflexic, rather than spastic and hyperreflexic as they should be in upper motor neuron paralysis. However, within several days, this spinal shock will disappear and signs of spasticity will become evident. The three main conditions to be considered in the differential diagnosis are: acute spinal cord trauma, acute compressive lesions of the spinal cord such as epidural metastatic tumour, and infarction of the spinal cord, usually due to insufficiency of the anterior spinal artery. From the symptoms and signs, it may be very difficult to distinguish acute transverse myelitis from these conditions and it is almost invariably necessary to perform an emergency magnetic resonance imaging (MRI) scan or computerised tomographic (CT) myelogram. Before doing this, routine x-rays are taken of the entire spine, mainly to detect signs of metastatic disease of the vertebrae, that would imply direct extension into the epidural space and compression of the spinal cord. Often, such bony lesions are absent and it is only the MRI or CT that discloses the presence or absence of a compressive lesion. A family physician seeing such a patient for the first time should immediately arrange transfer to the care of a neurologist or neurosurgeon who can urgently investigate the patient in hospital. Before arranging this transfer, the physician should be certain that respiration is not affected, particularly in high spinal cord lesions. If there is any evidence of this, methods of respiratory assistance must be on hand before and during the transfer procedure. The patient should also be catheterized to test for and, if necessary, drain an over-distended bladder. A lumbar puncture can be performed after the MRI or at the time of CT myelography. Steroids are often given in high dose at the onset, in hope that the degree of inflammation and swelling of the cord will be lessened, but whether this is truly effective is still debated. Unfortunately, the prognosis for significant recovery from acute transverse myelitis is poor in approximately 80% of the cases; that is, significant long-term disabilities will remain. Approximately 5% of these patients will, in later months or years, show lesions in other parts of the central nervous system, indicating, in retrospect, this that was a first attack of multiple sclerosis.

External links

• The Johns Hopkins Transverse Myelitis Center (JHTMC) (http://www.hopkinsmedicine.org/jhtmc/)
• The Transverse Myelitis Association (http://www.myelitis.org/)