A condition known as neuromyelitis optica (ner-oh-my-uh-LYE-tis AHP-tih-kuh) (NMO) was until recently regarded as a severe form of multiple sclerosis in its earliest stages.1,2 However, a recent study may help shed some light for physicians who find it difficult to distinguish NMO from MS, which share many of the same signs early on. It's based on a specific antibody found in the blood of individuals with NMO that isn't seen in MS patients.3
One key finding is that this diagnostic test may help doctors diagnose NMO at its early stages when it can be difficult to distinguish it from MS. "Ours is the first study to report a [blood] marker that is often positive from the first symptom of the disease," said Vanda Lennon, MD, PhD, and Brian Weinshenker, MD, two neurologists at the Mayo Clinic who took part in this study, in an interview with Priority Healthcare. "There are clinical and MRI differences that in aggregate differentiate NMO from MS, but these differences are not absolute, and differentiation is only possible in well established cases."
This is important, the researchers say, because treatment regimens for the two diseases are very distinct. "NMO patients are generally treated with immunosuppressant therapy, whereas MS patients are treated with immunomodulatory therapies such as interferon beta or glatiramer acetate as first line treatments," Lennon and Weinshenker said.
Because the two diseases have different treatment regimens, experts have pointed out that a test that distinguishes these disorders at the onset of symptoms would improve therapy outcomes.
NMO, also known as Devic's syndrome, is a rare autoimmune disorder of the central nervous system in which myelin, a fatty substance that protects nerve fibers and helps them communicate with each other, breaks down. Optic neuritis, inflammation of the optic nerve causing vision loss and eye pain, is often characteristic of the disease, as well. Symptoms of NMO include vision impairment and various degrees of paralysis, as well as incontinence.4
MS has similar pathological characteristics: the immune system mistakenly attacks myelin in the central nervous system, breaking it down and causing the symptoms seen in the disease.5
Overlapping Characteristics Make Diagnosis Difficult
While full-blown NMO can be distinguished from MS using a combination of clinical, imaging, and spinal fluid tests, its initial symptoms are commonly mistaken for an MS attack. "Optic neuritis and myelitis, the cardinal features of NMO, both occur in patients with MS," explained Lennon, a professor of Immunology, as well as Neurology, and Weinshenker, also a professor of Neurology, both at the Mayo Clinic College of Medicine.
As an example, in Japan, nearly a third of NMO cases are mistaken as multiple sclerosis, Lennon and Weinshenker told Priority Healthcare.
A Biological Tip
Making this distinction was a goal of this study by Lennon, Weinshenker, and their colleagues at the Mayo Clinic and Tohoku University School of Medicine in Sendai, Japan. Through a series of lab studies, the investigators led by Lennon identified an autoantibody that is specifically present in the blood of many people with NMO. Autoantibodies are proteins produced by the immune system that mistakenly attack tissues in the body, believing they are foreign.
Based on studies using mice, Lennon and her team found that this autoantibody attaches to discrete regions of the brain and spinal cord tissues.
To determine how specific the autoantibody is to the pathology of NMO, the researchers examined blood samples taken from 124 people with the disease, and compared them to samples taken from a group of 75 people with multiple sclerosis and other neurological disorders. None of the researchers were aware which samples were taken from NMO patients and which were collected from those with MS.
No Connection to MS
In the end, Lennon's group found the autoantibody in the samples of three-quarters of NMO patients, in nearly half of those classified as being at high risk for developing NMO, and in none of those diagnosed with MS or other neurological or autoimmune disorders.
Lennon and her colleagues suggested that this biological marker is sufficiently strong enough to be used to diagnosis people with NMO as distinguished from people with MS, especially when symptoms make distinguishing the two illnesses difficult. However, she added that testing for the autoantibody would not completely replace the traditional clinical, imaging, and spinal fluid tests that are currently used.
In a bulletin about the study, the National Multiple Sclerosis Society stated: "A positive result can help a neurologist to identify people at risk for NMO early in the course of the disease, allowing appropriate treatment to be initiated early and hopefully reduce the damage caused by this disease. The test may also be used to track response to treatment."
1. Stadelmann C, Bruck W. Lessons from the neuropathology of atypical forms of multiple sclerosis. Neurol Sci 2004 Nov;25 Suppl 4:S319-22.
2. Dupel-Pottier C. Diagnostic criteria of borderline forms of multiple sclerosis. [Translated from French]. Rev Neurol (Paris) 2001 Sep;157(8-9 Pt 2):935-43.
3. Lennon VA, Wingerchuk DM, Kryzer TJ et al. A serum autoantibody marker of neuromyelitis optica: distinction from multiple sclerosis. Lancet 2004 Dec 11;364(9451):2106-12.
4. National Institute of Neurological Disorders and Stroke. National Institutes of Health (NIH). What is Devic's Syndrome? Available at: http://www.ninds.nih.gov/disorders/devics/devics.htm. Accessed March 24, 2005.
5. National Multiple Sclerosis Society. What is Multiple Sclerosis? Available at: http://www.nationalmssociety.org/What%20is%20MS.asp. Accessed March 24, 2005.
John Martin is a long-time health journalist and an editor for Priority Healthcare. His credits include coverage of health news for the website of Fox Television's The Health Network, and articles for the New York Post and other consumer and trade publications.