Myelitis

Definition, Etiology, PathogenesisTop

Myelitis is an inflammatory process involving the nervous tissue of the spinal cord. It is caused by the presence of microorganisms in the tissue. The most common causative factor is a viral infection, including infections caused by enteroviruses (coxsackieviruses A and B, echovirus, poliovirus, enteroviruses type 70 and 71), herpesviruses (herpes simplex virus [HSV], varicella-zoster virus [VZV], cytomegalovirus [CMV], Epstein-Barr virus [EBV]), and HIV. Myelitis may develop in the course of neuroborreliosis, leptospirosis, neurosyphilis, and central nervous system (CNS) tuberculosis.

Clinical Features and Natural HistoryTop

The presenting symptom may be weakness, back pain, or both.

1. Involvement of anterior horn cells: Currently, etiologic factors are predominantly enteroviruses. The involvement manifests as acute progressive asymmetric flaccid paralysis, which usually affects all extremities, is associated with muscle weakness, persists for several days, and is accompanied by fever and myalgia. No sensory deficits are present. Bulbar involvement may lead to dysphagia and respiratory failure.

2. Transverse myelitis: Ascending flaccid paralysis, sensory deficits, and sphincter dysfunction.

3. Myelitis in the course of meningitis, encephalitis, or meningoencephalitis: A combination of signs and symptoms typical for the respective clinical syndrome. In some patients features of a particular viral disease may also be present (although their absence does not exclude viral myelitis).

Many patients develop permanent neurologic deficits, including sensory deficits and paresis and paralysis of various extent and patterns. Any delay in the initiation of treatment increases the risk of permanent neurologic sequelae.

DiagnosisTop

Magnetic resonance imaging (MRI) should be performed as soon as possible in every patient with suspected myelitis (this also allows to exclude noninflammatory abnormalities leading to spinal cord compression). Microbiologic and serologic studies: see Encephalitis; see Meningitis. Routine cerebrospinal fluid (CSF) analysis (see Laboratory Tests) reveals features of inflammation; viral etiology is characterized by a predominance of mononuclear cells and significantly elevated protein levels (patients with poliomyelitis initially have pleocytosis with normal protein levels; after ~2 weeks cell numbers return to normal while protein levels increase). Tuberculosis is associated with very high protein levels.

Treatment and PreventionTop

See Encephalitis; see Meningitis. Treatment of inflammation and edema (dexamethasone) is of vital importance. In case of spinal cord compression by an epidural abscess, perform emergency surgery (decompression).