Symptoms include weakness and numbness of the limbs as well as motor, sensory, and sphincter deficits. Severe back pain may occur in some patients at the onset of the disease. 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 upper cervical cord 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 (C5–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 upper motor neuron signs in the lower limbs, presenting as a spastic diplegia.
• 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 pain 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.

Some patients have also described the feeling of their abdominal area being in a binder^{[citation needed]}.

However, within several days, this spinal shock will disappear and signs of spasticity will become evident.

Transverse myelitis can appear for several reasons. Sometimes the disorders classified as such can be referred to as "Transverse myelitis spectrum disorders"^[2]

In some cases, the disease is presumed to be caused by viral infections such as cytomegalovirus (CMV) and has also been associated with spinal cord injuries, immune reactions, schistosomiasis and insufficient blood flow through spinal cord vessels. Acute myelitis accounts for 4 to 5 percent of all cases of neuroborreliosis.^[3]

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.

Another possible cause is dissection of the aorta, extending into one or more of the spinal arteries.

Transverse myelitis can be a rare complication following cat scratch disease.^[4] As well as it can be associated with : Bacterial Infections-Mycoplasma pneumoniae, Lyme borreliosis, syphilis (tabes dorsalis), tuberculosis. Viral Infections-herpes simplex, herpes zoster, cytomegalovirus, Epstein-Barr virus, enteroviruses (poliomyelitis, Coxsackie virus, echovirus), human T-cell, leukemia virus, human immunodeficiency virus, influenza, rabies. Post-Vaccination-Rabies, cowpox. Multiple Sclerosis. Paraneoplastic syndromes. Vascular-Thrombosis of spinal arteries, vasculitis secondary to heroin abuse, spinal Arteriovenous malformations.

This demyelination arises idiopathically following infections or due to multiple sclerosis (and has been reported to occur following vaccination^[5]). One major theory posits that immune-mediated inflammation is present as the result of exposure to a viral antigen. The diarrhea-causing bacteria Campylobacter jejuni is also a reported cause of transverse myelitis.^[6]

The lesions are inflammatory, and involve the spinal cord typically 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 they are usually restricted to only a small portion.

A special case is the "Longitudinally extensive transverse myelitis" (LETM) which is defined as a spinal cord lesion that extends over 3 or more vertebral segments.^[7]