Mayo Clinic develops new criteria for early, accurate diagnosis of multiple sclerosis variant

Monday, July 03, 2006

Scottsdale, Ariz. — Specific, measurable criteria by which neuromyelitis optica (NMO) can be distinguished from standard multiple sclerosis (MS) shows promise in understanding demyelinating diseases, according to researchers at Mayo Clinic.

NMO is one of several diseases that cause damage to the myelin sheath surrounding the nerve fibers in the body's central nervous system. The resulting damage, called demyelination, impairs a patient's vision, movement, strength and sensation by hindering the transmission of electrical impulses throughout the body.

Results of the research were published in the May 23, 2006, issue of Neurology, the journal of the American Academy of Neurology. Lead author of the paper was Dean Wingerchuk, M.D., Neurology, Mayo Clinic in Arizona.

Since NMO and MS exhibit such similar symptoms, the two have historically been considered to be variations of the same condition. Only in the past decade has it become clear that significant differences exist in the prognosis and treatment of the two ailments.

The two also differ in which segments of the population they afflict. Typical MS attacks women more frequently than men by a 2-1 margin, while NMO is found in women at an even higher rate — 4 to 5 times greater than men. Also, while NMO is found in Caucasians, it is over-represented among racial minorities such as Hispanics, African Americans and Asians.

A key component in the criteria to accurately identify NMO is a blood test devised in 2004 by Vanda Lennon, M.D., Mayo Clinic in Rochester, a member of the same research team. That test, which identifies a bio-marker called NMO-IgG, can be combined with clinical observation and MRI studies to give neurologists a high degree of confidence in their diagnosis of NMO, permitting prompt treatment.

The blood test has also provided medical professionals with better evidence about how frequently NMO appears. "We've learned there are many people who fit within the NMO spectrum who in the past were believed to have MS," says Dr. Wingerchuk. "This is the first blood test that's ever been validated relative to MS that has the ability to help confirm a diagnosis. That's very important in getting patients on the right treatment quickly because we treat NMO and MS differently."

The identification of the NMO-IgG antibody may also be a clue to what actually causes NMO. Once the antibody NMO-IgG was successfully identified, Dr. Lennon's laboratory team was able to identify the specific protein — called aquaporin-4 — that is targeted by NMO-IgG. This targeting of aquaporin-4 "might trigger the onset of NMO," says Dr. Wingerchuk.

Mayo Clinic is a private group practice of medicine dedicated to providing diagnosis and treatment of patient illnesses through a systematic focus on individual patient needs. As a leading academic medical center in the Southwest, Mayo Clinic focuses on providing specialty and surgical care in more than 65 disciplines at its outpatient facility in north Scottsdale and at Mayo Clinic Hospital. The 208-licensed bed hospital is located at 56th Street and Mayo Boulevard (north of Bell Road) in northeast Phoenix, and provides inpatient care to support the medical and surgical specialties of the clinic, which is located at 134th Street and Shea Boulevard in Scottsdale.

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