New diagnostic criteria have been introduced for neuromyelitis optica (NMO), which is now to be known as neuromyelitis optica spectrum disorder (NMOSD).
The new criteria were developed by an international consensus panel, headed by Dean Wingerchuk, MD, from the Mayo Clinic, Rochester, Minnesota, which reviewed the medical literature on NMOSD. The recommendations were published in the July 14 issue of Neurology.
They explain that NMOSD is an inflammatory disease of the central nervous system that can affect the optic nerves, brain stem, spinal cord, and brain. It can be mistaken for multiple sclerosis, but accurate diagnosis is essential because some drugs used for multiple sclerosis can worsen NMSOD.
NMOSD can cause a spectrum of symptoms, including visual loss, paralysis and episodes of persistent hiccups, nausea, and vomiting. A blood test to detect aquaporin-4 IgG antibodies (AQP4-IgG) is highly specific for NMOSD and facilitates the diagnosis, but some patients have the key features of NMOSD yet no detectable antibodies. The new criteria address both possibilities.
"It's very important for clinicians to know about these updated criteria," said Dr Wingerchuk. "An accurate diagnosis is necessary for selecting the right therapy."
"In the past the previous criteria for a diagnosis of NMO required that the patient had both optic neuritis and transverse myelitis. And these are still the most common symptoms. But the new criteria allow other symptoms to be taken into account as well. These include postrema clinical syndrome characterized by intractable hiccups or nausea and vomiting, and other criteria involving the brainstem such as double vision or ataxia," he told Medscape Medical News.
"If a patient has any of these symptoms or an MRI scan with suggestive findings then an antibody test should be obtained. The new criteria allow for a diagnosis of NMOSD after a single attack if the antibody test is positive. It also allows the diagnosis to be given if the antibody test is negative under more stringent criteria. We believe more people will be captured after their first attack with these new criteria, which will lead to earlier and more accurate diagnosis."
The authors note the new consensus definition of NMOSD unifies traditional NMO and modern NMOSD definitions.
"It allows for NMOSD diagnosis in AQP4-IgG–seropositive patients with involvement of almost any CNS [central nervous system] region as well as in those with restricted involvement of a single region (eg, recurrent transverse myelitis)," they write.
For the first time, criteria allow for an NMOSD diagnosis in patients who have not experienced clinical involvement of optic nerves or spinal cord.
Core clinical characteristics of NMSOD are listed as:
Optic neuritis
Acute myelitis
Area postrema syndrome: episode of otherwise unexplained hiccups or nausea and vomiting
Acute brainstem syndrome
Symptomatic narcolepsy or acute diencephalic clinical syndrome with NMOSD-typical diencephalic MRI lesions
Symptomatic cerebral syndrome with NMOSD-typical brain lesions.
The new diagnostic criteria for NMOSD require at least one of the above core clinical characteristic with a positive result on an antibody test (cell based assay recommended).
If the antibody test result is not positive, then the patient must have at least two core clinical characteristics (one of which must be optic neuritis, acute myelitis with longitudinally extensive transverse myelitis lesions, or area postrema syndrome) and must also show additional MRI requirements.
The additional MRI requirements are as follows:
Acute optic neuritis: requires brain MRI showing (1) normal findings or only nonspecific white matter lesions or (2) optic nerve MRI with T2-hyperintense lesion or T1-weighted gadolinium enhancing lesion extending over 1/2 optic nerve length or involving optic chiasm
Acute myelitis: requires associated intramedullary MRI lesion extending over three contiguous segments or at least three contiguous segments of focal spinal cord atrophy in patients with history compatible with acute myelitis
Area postrema syndrome: requires associated dorsal medulla/area postrema lesions
Acute brainstem syndrome: requires associated periependymal brainstem lesions
In an accompanying editorial, Ilya Kister, MD, New York University School of Medicine, New York, and Friedemann Paul, MD, Charité University Medicine Berlin, Germany, point out that in just over a decade, "NMO has been transformed from an obscure, untreatable disorder…into a distinct nosologic entity with its own serologic marker and a wide range of as yet unproven, but universally deployed treatment options."
They attribute this "remarkable change of fortune" to the breakthrough discovery of AQP4-IgG antibody test, which they say is "exquisitely specific to NMO."
While the editorialists agree that the new diagnostic criteria will aid earlier identification of these patients and that it will be "highly desirable to identify and treat NMOSD after the first attack," there is still a risk for misdiagnosis with both false-positive and false-negative results.
They note that the use of cell-based assays for AQP4-IgG would help reduce the problem of misdiagnosis, but these are not widely available.
They add that "the best antidote to diagnostic error is a thorough familiarity with the clinical and paraclinical features that increase or decrease pretest probability of NMOSD" and point out that the new review document includes several useful examples in this regard.
These include the observation that onset-to-nadir time of less than 4 hours, or an inexorably progressive course, would be highly atypical for NMO myelitis. In addition, the presence of coexisting systemic lupus erythematosus, Sjögren syndrome, or myasthenia gravis increases confidence about NMOSD diagnosis, while extraneural sarcoidosis makes it less likely.
The International Panel for Neuromyelitis Optica Diagnosis was supported by the Guthy-Jackson Charitable Foundation. Dr Wingerchuk has received research support from Alexion, Terumo BCT, and the Guthy Jackson Charitable Foundation; receives financial compensation for participation on a relapse adjudication panel for MedImmune; and has served as a consultant to Alexion, MedImmune, and Chugai Pharmaceuticals. Other members of the panel receive royalties for a technology license related to a test for aquaporin-4 autoantibodies for diagnosis of neuromyelitis optica. Both editorialists are members of International Clinical Consortium of the Guthy-Jackson Charitable Foundation.
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Cite this: New Name, Diagnostic Criteria for Neuromyelitis Optica - Medscape - Jul 17, 2015.
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