Neuromyelitis Optica or Devic's Disease: What Is It?
Autoimmune diseases are a group of pathologies in which the cells in charge of the body’s defense attack their own organs. Such is the case with neuromyelitis optica (NMO), a disease involving the demyelination of certain areas of the central nervous system (CNS).
A substance called myelin covers the entire CNS and is involved in the correct transmission of nerve impulses. And in the case of neuromyelitis optica, specific antibodies will attack proteins in the spinal cord and optic nerve, Aquaporins 4, altering their correct functioning.
This condition is also known as Devic’s disease and has a relapsing form of presentation. In fact, relapses occur in 70% of the cases. The most frequent symptoms are alterations having to do with inflammation of the optic nerve and spinal cord.
The similarities and differences between neuromyelitis optica and multiple sclerosis
Multiple sclerosis (MS) is an autoimmune disease that also attacks the central nervous system, making it easy to confuse with NMO. In fact, for many years, experts considered neuromyelitis optica to be a type of multiple sclerosis.
The two pathologies in question affect the structures that make up the central nervous system, causing demyelination, and both affect the spinal cord. However, while MS is capable of altering various encephalic structures, NMO only affects the optic nerve.
The symptomatology presented by patients is very similar, as both have recurrent and single presentations. At the same time, people with multiple sclerosis also experience optic neuritis and myelitis, so visual and sensory problems are frequent.
The main difference between the two is the humoral alteration in neuromyelitis optica. Studies have shown that most patients with NMO have anti-aquaporin 4 antibodies, which are very rare in people with MS.
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Symptoms of neuromyelitis optica
As already stated, the clinical presentation of people with NMO will have to do with optic neuritis and transverse myelitis. It may be bilateral or unilateral, in addition to altering a structure of the optic nerve called the optic chiasm. Among the most relevant ophthalmologic symptoms are the following:
- Decreased visual acuity
- Loss of vision
- Ocular pain
- Eye fatigue
- Oculomotor dysfunction
At the same time, the spinal cord will also be affected by an inflammatory process in at least 3 segments. Therefore, neurological symptoms may appear. In this sense, the main alterations include the following:
- Inability to move one or more limbs
- Alterations in sensitivity
- Loss of sphincter control
- Muscle spasms
- Nausea and vomiting
Individuals with neuromyelitis optica experience relapse between 2 and 3 years after the initial episode. Neuromyelitis optica is more common in women over 39 years of age. What’s more, studies show that motor impairment in women is usually worse than in men.
Diagnosing neuromyelitis optica
Making an accurate diagnosis of this disease can be a complex task for specialists, requiring a series of different tests. In this regard, the physician must make the distinction with other neurological pathologies.
Anti-aquaporin 4 antibodies
One of the main findings guiding the diagnosis of neuromyelitis optica is the presence of anti-aquaporin 4 antibodies in the bloodstream. These antibodies are found in more than 70% of patients with the disease. Therefore, they’re a clear indication.
These molecules are responsible for the destruction of aquaporin 4 in the CNS and subsequent demyelination. Despite being a recent discovery, it’s proven useful in early diagnosis.
Read also: What Are Antigens and Antibodies?
Magnetic resonance imaging (MRI) is the imaging study of choice used in this case. The test uses magnets and radio waves to create a detailed image of CNS structures. Physicians can detect damage at the brain or spinal cord level.
Patients with neuromyelitis optica will have an obvious lesion in the spinal cord, usually at the level of the second thoracic vertebra. This will repeat in three consecutive spinal cord segments. Also, this examination determines that the only brain structure affected is the optic nerve.
Cerebrospinal Fluid (CSF) Studies
Specialists may remove a small amount of cerebrospinal fluid for CSF analysis. The fluid in question shows an elevated amount of proteins and white blood cells when neuritis is present. This is higher than that in patients with multiple sclerosis.
Presence of diagnostic criteria
Since 1999, a set of criteria have been established that are present in all patients with neuromyelitis optica. These were modified in 2006. In total 3 definitive criteria indicate the presence of the disease:
- Neuromyelitis optica
- Acute myelitis
- Absence of clinical disease outside the spinal cord and optic nerves
Treatment of neuromyelitis optica
The symptomatology of the disease is due to an inflammatory process. Therefore, the use of corticosteroids helps to reduce the impact of the signs. Also, this type of medication prevents future relapses.
When corticosteroids fail to improve symptoms, plasma exchange may be necessary. This procedure consists of removing blood from the body and then separating the plasma or fluid from the cells and replacing it with a synthetic analog.
Plasma exchange is a process that can take hours and must be performed multiple times. Finally, the doctor prescribes immunosuppressive drugs. These decrease the activity of the immune system, thereby reducing damage to CNS structures.
Dietary recommendations for individuals with NMO
All patients with a diagnosis of NMO should make a change towards a healthier lifestyle. Doing so avoids or slows the progression of the disease. Specifically, dietary modifications are crucial.
So, a nutritionist needs to monitor patients to help them follow an adequate plan according to the pathology they present. Among the recommendations they can follow are the following:
- Increase the intake of vegetables: Fruits, cereals, and grains
- Decrease foods rich in saturated fats and carbohydrates
- Drink 5 to 8 glasses of water or sugar-free fluids per day
- Eliminate alcohol and coffee consumption
NMO: A difficult disease to diagnose
In conclusion, neuromyelitis optica is a degenerative autoimmune disease with ocular and neurological symptoms. Although this pathology is easy to confuse with other CNS diseases, diagnostic methods have advanced greatly.
Unfortunately, there’s no specific treatment for this disease. However, corticosteroids and immunosuppressants help the patient to improve. Finally, people with NMO need to make lifestyle changes to prevent progression and relapses.