Transverse myelitis (TM) refers to a segmental inflammatory process involving the spinal cord, and may be idiopathic or secondary to a variety of specific disease processes. It typically presents with acute or subacute flaccid paraparesis, sensory abnormalities, and bowel/bladder dysfunction. When complete, both the anterior and posterior regions of the cord are involved; partial TM cord syndromes (those not involving the transverse span of the cord or those with mild symptoms of myelitis) are more commonly associated with multiple sclerosis than are complete TM syndromes. On examination, patients with acute TM may have bilateral lower motor neuron weakness, hyporeflexia, a spinal sensory level, and impaired joint position discrimination. Hyperacute onset and sparing of joint position discrimination should raise suspicion for anterior spinal artery cord infarction. Subacute and chronic TM typically evolves to demonstrate hyperreflexia and other upper motor neuron signs weeks after initial presentation.
Compressive spinal cord lesions may present with the same symptoms as TM and must be identified, as emergent decompressive surgery is indicated in such cases. Spine magnetic resonance imaging (MRI) is the preferred diagnostic test; in patients unable to undergo MRI, computed tomography (CT) or CT myelography may be used. Spinal cord infarction (see Chapter 47) and, rarely, spinal cord edema/ischemia from a spinal cord dural arteriovenous fistula can clinically mimic TM. Central T2 hyperintensity, particularly involving the anterior horns, is the classic MRI finding in cord infarction. Flow voids on the cord surface on T2 sequences are commonly but not uniformly seen in dural fistulas. Additional imaging such as cord MRI diffusion weighted imaging or catheter angiography may be necessary to clarify the diagnosis. If MRI is normal, consider Guillain-Barré syndrome.
If a lesion consistent with TM is found, start high-dose intravenous steroids immediately to reduce cord inflammation. Progression from onset to nadir in TM occurs between 4 hours and 21 days. Steroids may prevent progression and improve recovery. It is acceptable to start and continue steroids while determining the underlying cause of TM. Even if an infectious cause is present, steroids are generally safe.
Cerebrospinal fluid (CSF) examination is required for specific testing and to evaluate for inflammation. In addition to routine studies, check oligoclonal bands, IgG index, and cytology. Additional testing should be tailored to individual patient features (see below).
An intrinsic cord lesion spanning three or more segments suggests certain specific causes are more likely, but it does not absolutely rule in or out any type of inflammatory myelitis.
Neuromyelitis optica spectrum disorders (NMOSDs) are severe inflammatory diseases with a predilection for the spinal cord and optic nerves. Most cases are associated with aquaporin-4 antibodies (known as NMO antibody). Up to 40% of NMOSD patients with a negative NMO antibody have anti-myelin oligodendrocyte glycoprotein (MOG) antibodies.
TM related to multiple sclerosis is rarely associated with significant CSF pleocytosis. If suspected, brain MRI should be performed to look for cerebral demyelinating lesions. When > 20 white blood cells (WBC)/mm 3 are present in the CSF, consider infectious agents, noting that noninfectious conditions such as NMOSD and neurosarcoidosis can also have significant pleocytosis.
Serologic testing is indicated to identify common and uncommon cause of TM, many of which are often overlooked. For most TM patients, this should include testing for human immunodeficiency virus (HIV), syphilis, Lyme disease (if in an endemic area), and antinuclear, antiphospholipid, Sjogren’s Syndrome A/Ro (SS-A), Sjogren’s Syndrome B/La (SS-B), NMO, and MOG antibody testing. B12 and copper deficiency typically cause a more chronic myelopathy, but they should be checked if there is uncertainty about the temporal course. In rare cases, TM may be associated with paraneoplastic disorders, particularly in association with lung and breast cancer. Specific autoantibodies associated with myelitis are collapsing response mediator protein-5-IgG (CRMP5 or anti-CV2), amphiphysin-IgG, anti-Hu (ANNA-1), anti-Ri (ANNA-2), and ANNA-3. Infectious causes should be evaluated in patients with significant CSF pleocytosis (> 20 WBC/mm 3 ) or with clinical features suggesting infection. Herpes simplex, varicella zoster, and Epstein-Barr virus polymerase chain reaction (PCR), and in immunocompromised patients, cytomegalovirus PCR, can be checked in CSF. In motor-predominant TM (acute flaccid paralysis), West Nile (if in an endemic area), and enterovirus PCR should be considered.
Other tests that are useful in certain patients to determine the underlying cause are chest CT (sarcoidosis, malignancy), salivary gland or lip biopsy (Sjögren syndrome), and meningeal biopsy (undiagnosed, persistent meningeal enhancement).
Patients with no or poor response to steroids within ~ 15 days should be offered plasmapheresis, typically given as five treatments over 10–14 days. Anti-MOG NMSOD patients may respond to prolonged courses of steroids. Some degree of recovery is eventually seen in most patients with idiopathic TM, though residual disability is not uncommon. Recovery from myelitis associated with specific infections is highly variable.