Demyelinating diseases
GENERAL ASPECTS
We speak of demyelinating diseases to refer to the group of pathologies characterized by myelin damage. Neurons transmit orders and receive information in the form of nerve impulses through axons. Myelin is the sheath that covers the axon, increases conduction velocity and is essential to protect it. Its injury causes difficulties in the connectivity between the different areas of the central nervous system and can manifest itself in the form of motor, visual and sensory symptoms, gait or balance disorders, among others.
The most frequent demyelinating pathology is Multiple Sclerosis. It is more prevalent in women and the age of onset usually ranges between 20 and 40 years of age, although it can also manifest itself in children or, later, in older people. It is a chronic disease, is a frequent cause of disability and its most common form is Recurrent Remitting Sclerosis, which occurs in the form of outbreaks. About 10% of people with Multiple Sclerosis have an onset without outbreaks, with symptoms that worsen progressively, mainly with gait disturbance. In these cases we speak of Primarily Progressive Multiple Sclerosis.
What is its cause?
Multiple Sclerosis is an autoimmune disease. We do not know exactly why the immune system reacts by damaging the myelin but we do know that there are some factors that favor it. It is important to note that it is not a hereditary disease. We do know that there is a genetic predisposition on which environmental factors act. The risk increases if we have first-degree relatives affected. It is more frequent in white people. Likewise, the prevalence is higher in regions located at higher latitudes, with the risk decreasing as we approach the equator.
Regarding possible environmental factors, the appearance and development of the disease has been related to infection by the Epstein-Barr virus, low levels of vitamin D, obesity, smoking or changes in the intestinal microbiota.
DIAGNOSIS
What are the symptoms?
The most common form of Multiple Sclerosis, Recurrent Remitting Multiple Sclerosis, is manifested by a first outbreak that may present with motor symptoms, gait or balance disturbance, optic nerve inflammation with loss of visual acuity and eye pain, or sensory disturbances in the form of tingling, cramping or neuropathic pain. To suspect a flare, symptoms must remain constant for at least 24 hours.
People with Multiple Sclerosis may also present with other symptoms independently of flares such as fatigue, cognitive problems, spasticity, pain or urinary symptoms.
How is it diagnosed?
For the diagnosis, it is essential to perform a brain MRI and, usually, also a spinal MRI, where we can see demyelinating plaques, which are those areas where myelin inflammation is visible. Depending on the location and morphology of the lesions and following the Mc Donald diagnostic criteria, modified in 2017, the neurologist will confirm whether the MRI findings meet the criteria for Multiple Sclerosis. Usually the study is performed with contrast (gadolinium). Lesions with active inflammation capture contrast.
Generally, the neurologist will perform more complementary tests to differentiate Multiple Sclerosis from other possible pathologies and ensure the diagnosis, such as a complete blood test, a study of visual, auditory and/or somatosensory evoked potentials and a lumbar puncture. Performing a lumbar puncture is a common practice since it may be essential for diagnosis in many cases, as in the case of a first outbreak, and it provides information on the prognosis.
TREATMENT
Do you have treatment?
Yes, at the present time we have multiple treatments that act on the immune system modifying the evolution of the disease. The drugs reduce the risk of new outbreaks, reduce the risk of new lesions appearing on MRI and improve the prognosis. Early diagnosis is important to start treatment at the right time and a follow-up by a specialist neurologist to choose the drug indicated in each case. Injectable, oral and intravenous infusion drugs are available. Each of them acts in a different way on the immune system and has a different level of efficacy and risks. The choice of treatment is a complex process and requires a personalized benefit-risk assessment for each person with Multiple Sclerosis.
In addition to immunomodulatory treatment, the neurologist may consider other treatments aimed at controlling symptoms such as spasticity, pain or fatigue.
FREQUENT QUESTIONS
Can lifestyle habits influence the evolution of the disease?
It is recommended to maintain adequate levels of vitamin D, being necessary a control by the neurologist in case supplementation is required. Obesity probably worsens the prognosis by generating a proinflammatory state. There is data on the negative influence of smoking on the risk of progression. It is advisable to avoid alcohol consumption and to maintain a Mediterranean diet rich in oily fish, fruits, vegetables and legumes, as well as low in saturated fatty acids. Physical activity and neurological rehabilitation are beneficial as they generate mechanisms that favor the reorganization of damaged neuronal networks, although supervision by a specialist is recommended to avoid injuries and to carry out an adequate exercise program.
AUTHOR AND DATE OF ISSUE
Dr. Fernando Pérez Parra
18/06/2020
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