Demyelinating diseases consists of a group of disorders characterized by the loss of myelin with relative axonal sparing. Primary demyelinating disorders may be attributed to autoimmune mechanisms. Demyelination is often secondary to infectious, metabolic, ischemic, or hereditary disorders or exposure to a toxin.
Symptoms of demyelinating disorders are variable and depend on the neurologic deficits in the affected portion of the nervous system. Primary demyelinating disorders should be considered in patients presenting with diffuse or multifocal neurologic deficits of acute onset that wax and wane; in particular those that onset shortly after a vaccination or infection. The most common presenting symptom of demyelinating diseases are sensory disturbances of the limbs, vision loss, and subacute motor symptoms (e.g, weakness, spasticity, hyperreflexia, gait and balance disturbance) .
Common demyelinating disorders and presenting symptoms include:
The diagnosis of demyelinating disease consists of a history of present illness, physical exam, laboratory, neuromuscular and imaging tests. A history of any recent infections and/or vaccinations should be noted.
Laboratory tests that should be done include complete blood count, syphilis test (e.g., RPR), antinuclear antibodies, fluorescent treponemal antibody test, lyme titer, sedimentation rate, and angiotensin converting enzyme level .
A cerebrospinal fluid (CSF) exam may demonstrate pleocytosis (slight elevation of mononuclear white blood cells), oligoclonal immunoglobulin G (IgG) bands, and an elevated globulin to albumin ratio . Patients with myelin damage will have elevated CSF myelin protein levels, which is indicative of myelin damage.
A magnetic resonance imaging (MRI) scan may show subclinical demyelinated lesions and/or enhancement of nerve roots with the use of gadolinium .
The "hot bath test" works by elevating the body's temperature, which leads to exacerbation of symptoms and worsened deficits in persons with demyelinating disease.
Neuromuscular testing including an electromyography (EMG) can be used to help determine presence of peripheral neuropathy and demyelination .
A sural nerve biopsy can be performed to add to the evidence for the diagnosis of a demyelinating disease.