Neuromyelitis Optica, Part 2
In my previous post, I introduced the diagnostic criteria for NMO. There are many similarities between MS and NMO, but there are many important differences. Like MS, patients with NMO suffer from relapses, though the relapses are generally restricted to the optic nerves and spinal cord. When brain lesions in NMO patients do become symptomatic they sometimes produce a unique symptom: intractable hiccups and nausea. One small review of 35 patients with NMO found that 15 patients (43%) had episodes of intractable hiccups and nausea. Though I certainly cannot claim to have seen a large number of MS patients suffer from this symptom, in the few cases I have seen it, I always reconsider whether or not the patient has NMO instead.
Compared with MS, relapses in NMO are generally more severe and patients tend to recover less from the attacks. Unlike MS, there does not seem to be a progressive phase of the illness. All of the disability comes from these relapses. Like MS, NMO occurs more commonly in women than in men, and in fact the illness is quite unusual in men. However, unlike MS, NMO is more common in African-Americans and people of Hispanic descent than Caucasians. In MS, the reverse is true.
Relapses in NMO are treated with intravenous steroids, as in MS, but the approved treatments for MS have no clear role in NMO. In fact, there are some studies suggesting they may actually worsen the disease. There are no large clinical trials of treatment options in NMO, but studies of small series of patients support the use of immunosupressive agents.
Most neurologists are now well aware of NMO. However, I still occasionally see people whom I believe have NMO, who are instead being treated for MS. If patients reading this have any concerns that their illness sounds more like NMO than MS, they should talk to their neurologist and consider having the NMO antibody test.
Below, I have included MRIs from a patient of mine with NMO. These MRIs illustrate the essential features of NMO and show how it is different from MS.
The MRI below is from a brain of a patient with NMO showing inflammation (circled in red) of both optic nerves as they come together to form a structure termed the optic chiasm. The inflamed area is white, whereas normally it is gray.
The MRI below shows the long, thick area of inflammation in the cervical spine in a patient with NMO. In this image, the white area inside the spinal cord shows the inflammation. A normal spinal cord should be a uniform gray color. Additionally the inflamed area of the spinal cord is thick and swollen. This type of lesion would not be characteristic of MS.
The image below is from a patient with MS, showing multiple small plaques of demyelination.