Myelitis is inflammation of the spinal cord which can disrupt the normal responses from the brain to the rest of the body, and from the rest of the body to the brain. Inflammation in the spinal cord can cause the myelin and axon to be damaged resulting in symptoms such as paralysis and sensory loss. Myelitis is classified to several categories depending on the area or the cause of the lesion; however, any inflammatory attack on the spinal cord is often referred to as transverse myelitis.
Types of myelitis
Myelitis lesions usually occur in a narrow region but can be spread and affect many areas.
Acute flaccid myelitis: a polio-like syndrome that causes muscle weakness and paralysis. Poliomyelitis: disease caused by viral infection in the gray matter with symptoms of muscle paralysis or weakness Transverse myelitis: caused by axonal demyelination encompassing both sides of the spinal cord Leukomyelitis: lesions in the white matter Meningococcal myelitis (or meningomyelitis): lesions occurring in the region of meninges and the spinal cord Osteomyelitis of the vertebral bone surrounding the spinal cord (that is, vertebral osteomyelitis) is a separate condition, although some infections (for example, Staphylococcus aureus infection) can occasionally cause both at once. The similarity of the words reflects that the combining form myel(o)- has multiple (homonymous) senses referring to bone marrow or the spinal cord.
Symptoms Depending on the cause of the disease, such clinical conditions manifest different speed in progression of symptoms in a matter of hours to days. Most myelitis manifests fast progression in muscle weakness or paralysis starting with the legs and then arms with varying degrees of severity. Sometimes the dysfunction of arms or legs cause instability of posture and difficulty in walking or any movement. Also symptoms generally include paresthesia which is a sensation of tickling, tingling, burning, pricking, or numbness of a person's skin with no apparent long-term physical effect. Adult patients often report pain in the back, extremities, or abdomen. Patients also present increased urinary urgency, bowel or bladder dysfunctions such as bladder incontinence, difficulty or inability to void, and incomplete evacuation of bowel or constipation. Others also report fever, respiratory problems and intractable vomiting.
Diseases associated with myelitis Conditions associated with myelitis include:
Acute disseminated encephalomyelitis: autoimmune demyelination of the brain causing severe neurological signs and symptoms Multiple sclerosis: demyelination of the brain and spinal cord Neuromyelitis optica or Devic's disease: immune attack on optic nerve and spinal cord Sjögren's syndrome: destruction of the exocrine system of the body Systemic lupus erythematosus: a systemic autoimmune disease featuring a wide variety of neurological signs and symptoms Sarcoidosis: chronic inflammatory cells form as nodules in multiple organs Atopy: an immune disorder of children manifesting as eczema or other allergic conditions. It can include atopic myelitis, which causes weakness. Immune-mediated myelopathies, heterogeneous group of inflammatory spinal cord disorders including autoimmune disorders with known antibodies
Cause Myelitis occurs due to various reasons such as infections. Direct infection by viruses, bacteria, mold, or parasites such as human immunodeficiency virus (HIV), human T-lymphotropic virus types I and II (HTLV-I/II), syphilis, lyme disease, and tuberculosis can cause myelitis but it can also be caused due to non-infectious or inflammatory pathway. Myelitis often follows after the infections or after vaccination. These phenomena can be explained by a theory of autoimmune attack which states that the autoimmune bodies attack its spinal cord in response to immune reaction.
Mechanism of myelitis The theory of autoimmune attack claims that a person with neuroimmunologic disorders have genetic predisposition to auto-immune disorder, and the environmental factors would trigger the disease. The specific genetics in myelitis is not completely understood. It is believed that the immune system response could be to viral, bacterial, fungal, or parasitic infection; however, it is not known why the immune system attacks itself. Especially, for the immune system to cause inflammatory response anywhere in the central nervous system, the cells from the immune system must pass through the blood brain barrier. In the case of myelitis, not only is the immune system dysfunctional, but the dysfunction also crosses this protective blood brain barrier to affect the spinal cord.
Infectious myelitis
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