main muscle of respiration, the diaphragm. Lesions of the lower cervical region (C5–T1) 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. Cervical lesions account for about 20% of cases. A lesion of the thoracic segment (T1–12) will produce upper motor neuron signs in the lower limbs, presenting as a spastic paraparesis. This is the most common location of the lesion, and therefore most individuals will have weakness of the lower limbs. A lesion of the lumbar segment, the lower part of the spinal cord (L1–S5) often produces a combination of upper and lower motor neuron signs in the lower limbs. Lumbar lesions account for about 10% of cases. Causes TM is a heterogeneous condition, that is, there are several identified causes. Sometimes the term Transverse myelitis spectrum disorders is used. In 60% of patients the cause is idiopathic. In rare cases, it may be associated with meningococcal meningitis When it appears as a comorbid condition with neuromyelitis optica (NMO), it is considered to be caused by NMO-IgG autoimmunity, and when it appears in multiple sclerosis (MS) cases, it is considered to be produced by the same underlying condition that produces the MS plaques. Other causes of TM include infections, immune system disorders, and demyelinating diseases. Viral infections known to be associated with TM include HIV, herpes simplex, herpes zoster, cytomegalovirus, and Epstein-Barr. Flavivirus infections such as Zika virus and West Nile virus have also been associated. Viral association of transverse myelitis could result from the infection itself or from the response to it. Bacterial causes associated with TM include Mycoplasma pneumoniae, Bartonella henselae, and the types of Borrelia that cause Lyme disease. Lyme disease gives rise to neuroborreliosis which is seen in a small percentage (4 to 5 per cent) of acute transverse myelitis cases. The diarrhea-causing bacteria Campylobacter jejuni is also a reported cause of transverse myelitis. Other associated causes include the helminth infection schistosomiasis, spinal cord injuries, vascular disorders that impede the blood flow through vessels of the spinal cord, and paraneoplastic syndrome. Pathophysiology This progressive loss of the fatty myelin sheath surrounding the nerves in the affected spinal cord occurs for unclear reasons following infections or due to multiple sclerosis. Infections may cause TM through direct tissue damage or by immune-mediated infection-triggered tissue damage. The lesions present are usually inflammatory.