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Diagnosis and Treatment of Neuromyelitis Optica
index episodes and the requirement of monophasic course, which were
Figure 1: Cervical Spinal Cord Magnetic Resonance
historically important distinguishing features from MS. In addition to optic
Imaging in the Sagittal Plane of a Neuromyelitis
neuritis and transverse myelitis that alone do not distinguish between
Optica Patient
NMO and MS, however, added specificity criteria were incorporated, the
most important of which was the presence of a ‘longitudinally extensive
A BC
spinal cord lesion.’ This is defined as a T2 signal lesion extending over
three or more vertebral segments in the context of an acute myelitis
attack on magnetic resonance imaging (MRI) scan (see Figure 1).
1
Asymptomatic (but not symptomatic) brain lesions detected on MRI were
allowed. NMO-IgG seropositivity
3
and the observation that symptomatic
brain lesions are compatible with a diagnosis of NMO led to the revision
of the criteria in 2006
13
(see Table 1). The essential clinical features of
NMO are optic neuritis and myelitis, which are usually more disabling
in NMO than when they occur in the context of MS.
1
Myelitis attacks are
frequently ‘complete’ (symmetrical and with motor, sensory and
sphincter involvement) rather than ‘partial.’ NMO optic neuritis attacks
are more frequently bilateral with persisting visual deficits more severe
than in MS. Brainstem syndromes are now recognized to be especially
common. Severe and intractable hiccups, nausea, and vomiting lasting
weeks to months may occur and may be the presenting symptom in
A: T1-weighted image showing areas of subtle intraparenchymal hypointensity. B: T1-weighted
image post-gadolinium contrast adminstration showing a C1–C4 enhancing lesion.
patients with NMO.
1,14,15
Occasionally patients may experience C: T2-weighted image showing an area of hyperintensity spanning from the medulla to C7.
encephalopathy due to transient vasogenic brain edema and may be
diagnosed as having posterior reversible leukoencephalopathy.
16
Table 1: Diagnostic Criteria for Neuromyelitis Optica
13
Neurological disability in NMO is related to the attacks and a secondary
progressive course is very uncommon, unlike MS.
17
Optic neuritis
Acute myelitis
Neuroimaging
At least two of the following three supportive criteria:
Spinal cord MRI in the acute phase of attack frequently demonstrates a
Contiguous spinal cord MRI lesions extending over ≥3 vertebral segments
Brain MRI not meeting diagnostic criteria for multiple sclerosis
central lesion, extending over three or more continuous vertebral
NMO-IgG seropositive status
segments. Gadolinium enhancement is usually present, but may be
IgG = immunoglobulin G; MRI = magnetic resonance imaging; NMO = neuromyelitis optica.
patchy. Acute lesions are usually hypointense on T1 imaging. Central
cavities or longitudinally extensive cord atrophy may be present in later
Figure 2: Brain Magnetic Resonance Imaging with
stages of lesion evolution.
1
Confluent small chronic spinal cord lesions in
Optic Chiasm Lesion
MS patients may conglomerate and appear as a long lesion and may be
mistaken for NMO; in NMO a spinal cord lesion usually results in a well-
AB
delimited long lesion when imaging is obtained acutely in the context of
a disease attack (see Figure 1). Enhancing lesions of the optic nerve or
optic chiasm may be observed in the acute phase of an optic neuritis
attack (see Figure 2). Brain MRI lesions are detected in approximately
60% of NMO patients. Even though most brain lesions encountered in
patients with NMO are non-specific and asymptomatic, lesions in the
brainstem and hypothalamus appear to be relatively characteristic. Brain
lesions occur more frequently in regions known to have high expression
of aquaporin-4 (AQP4).
18,19
Serological Testing
NMO-IgG is the disease biomarker found the in serum of NMO patients. In
2004, Mayo Clinic investigators identified a specific immunofluorescence
Brain T1-weighted magnetic resonance imaging (MRI) scan post-gadolinium contrast
administration showing an enhacing optic chiasm (arrows). A: Axial view. B: Coronal view.
pattern in a few NMO patients studied using a protocol to detect
paraneoplastic syndrome autoantibodies. That same pattern had been syndromes (recurrent longitudinally extensive transverse myelitis and
recognized in other patients whose sera had been referred for recurrent optic neuritis); and with controls (MS and other neurological or
paraneoplastic serology testing. When medical information on those autoimmune disease patients). The sensitivity and specificity of the test
patients whose sera had been identified strictly on serological basis was were 73 and 91%, respectively, for NMO versus MS, the entity with which
reviewed, the common clinical substrate was a history of severe and NMO is most commonly confused.
3
Several independent investigators
recurrent optic neuritis and/or myelitis. A prospective study was then have confirmed the presence of NMO-IgG using a variety of assays for
conducted with clinically defined NMO patients; individuals with high-risk anti-AQP4 antibody detection.
20–24
US NEUROLOGY 57
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