Neuromyelitis Optica
Devic's Syndrome: Multiple Sclerosis Variant Often Confused with MS
Jun 4, 2008
Neuromyelitis optica (NMO), which is also known as Devic’s syndrome, is an autoimmune disorder often confused with multiple sclerosis (MS). In the followings case history adapted from the journal Laboratory Medicine, a condition of neuromyelitis optica is differentiated from multiple sclerosis.
The Patient
The patient is a 22-year old African-American woman whose chief complaint during this visit was monocular blindness (affecting one eye). Previously, the patient had been hospitalized three times, twice within an 18 month period (once shortly after giving birth), complaining of left-sided weakness. On these prior occasions, brain and cervical spine MRI scans were negative and the weakness responded to steroids. She was presumed to have multiple sclerosis.
On a 3rd hospital visit, the patient did not respond to steroids but responded to a course of plasmapheresis. In plasmapheresis, which temporarily reduces autoantibodies, blood is drawn and the liquid plasma removed. The remaining blood cells and also plasma from healthy donors is transfused back into the patient.
Case History
On her present ER visit, the patient complained of having complete vision loss in her right eye for one week. Her vital signs and reflexes were normal although her gait was slightly affected. Her right pupil was fixed and dilated and did not respond to light. During her hospital stay, she responded to another course of plasmapheresis. A brain MRI was ordered to test for ocular neuritis, a condition that can occur in multiple sclerosis, or ocular myasthenia gravis.
Diagnostic Tests
An MRI of the patient’s cervical spine revealed T2 hyperintensity from the cervicomedullary junction to C7. An MRI of her thoracic spine revealed T2 hyperintensity from T2 to T7. The brain MRI and chest X-ray were negative.
Liver enzymes were slightly elevated and mild anemia was seen. The spinal fluid analysis showed a high level of myelin basic protein (MBP) although it was negative for oligoclonal bands. Blood tests for neuromyelitis optica (NMO) IgG antibodies were positive while tests for myelin antibodies, ANA, c-ANCA, P-anca, phospholipid antibodies, herpes and viral hepatitis were negative. Tests for hypercoagulation were normal.
Conclusion
The past episodes of acute myelitis and progressive neuropathy suggested that the patient had either:
- multiple sclerosis
- an idiopathic condition of neuromyelitis optica
- vitamin deficiencies
- vasculitis
- diabetes
- an infectious disorder.
The absence of brain lesions and the positive test results for neuromyelitis optica antibodies supported a diagnosis of neuromyelitis optica. The clinical presentation, however, was considered the strongest indicator. A brain MRI scan that is normal or demonstrates only non-specific white matter lesions is 94 percent sensitive and 96 percent specific for NMO.
Blood tests for NMO autoantibodies by immunofluorescence (IFA) help distinguish NMO from MS. The NMO IgG antibody test is positive in approximately 60-80 percent of individuals diagnosed with NMO. The test is 58 to 76 percent sensitive and 94 to 100 percent specific for NMO although a recently developed test reports a higher sensitivity.
Neuromyelitic optica
NMO, or Devic' syndrome, which may occur as one episode (monophasic) or as a relapsing condition more common in non-whites, is characterized by inflammation and swelling of the optic nerves causing orbital pain, decreased visual acuity, decreased color perception and scotomas (optic neuritis). Optic neuritis usually affects both eyes. Episodes of optic neuritis are accompanied by a demyelinating transverse myelitis after a period of weeks, months or even years.
Unlike MS, which is cell-mediated, NMO is humoral or antibody-mediated. The lesions in NMO are absent in the brain but present in at least 3 spinal segments whereas in MS the lesions tend to occur in brain matter. NMO affects the mortality rate, with respiratory failure causing death in one-third of affected patients. Regardless of treatment, 60 percent of patients with relapsing NMO become blind in at least one eye. In monophasic NMO blindness occurs in 22 percent of patients.
Resource:
Steffini Stalos, Vision Loss in a 22-Year-Old Woman, Laboratory Medicine, Case Studies, October, 2007; 605-608.
