Demyelinating Disease

What is Demyelinating Disease?

It is a group of many nervous system conditions characterized by the damage of the myelin sheath that covers the nerves. The functioning of myelin includes conducting the impulses through the nerves. Hence, damage to the myelin sheath disrupts or completely halts conduction of brain signals in the nerves involved in the conditions. The disorder can occur both in children and adults. Multiple Sclerosis is the primary demyelinating disorder, affecting people all over the world.

Myelin is mainly found around the axon of a nerve. It develops with the growth of the nerve, forming a protective insulating coat around it. The demyelination of nerves seriously affects the movements, cognition, sensation and other functions of patients.

The Demyelinating Disease Image Source: wikimedia

Demyelinating Disease Types

Classification of the demyelinating diseases is done on the basis of whether they are affecting the nerves of the central nervous system or of the peripheral nervous system.

Central Nervous System

Diseases resulting from demyelination of the central nervous system (CNS) nerves include:

• Multiple sclerosis (along with the similar disorders known as Idiopathic Inflammatory Demyelinating Diseases)
• Tabes Dorsalis
• Optic Neuritis
• Vitamin B12 deficiency
• Central Pontine Myelinolysis
• Devic’s disease
• Transverse Myelitis
• Leukodystrophies
• Progressive Multifocal Leukoencephalopathy

Peripheral Nervous System

Following are the diseases that occur due to demyelination of peripheral nervous system (PNS) nerves:

• Guillain-Barré syndrome, along with Chronic Inflammatory Demyelinating Polyneuropathy
• Charcot-Marie-Tooth Disease
• Anti-MAG peripheral neuropathy
• Copper deficiency

Demyelinating Disease Causes

Various types of this disease generally have different causes. Sometimes, these diseases can occur due to certain genetic factors while others may result from infectious agents or traumatic head injuries. Autoimmune reactions triggered by unknown causes can also lead to demyelination of verves. In some cases, the exact etiology of the damage remains unknown. A group of chemicals known as organophosphates commonly used in commercial insecticides like weed-killers, sheep dip and flea remedies for pets may also play a role in demyelinating nerves. Neuroleptics are considered to be possible causes of these disorders as well.

Various autoimmune diseases, including the following, can damage the myelin sheath:

• Devic’s Disease
• Schilder’s Disease
• Fibromyalgia
• Guillain-Barre Syndrome

Demyelinating Disease Pathophysiology

Doctors still do not know the exact mechanism of nerve demyelination; however, there is considerable evidence that proves at least a partial involvement of the immune system of patients. An Acquired immune system cell, known as the T-cell, is often found at the sites of the lesion. Another similar cell named Macrophage (and most likely the Mast cell) is another important contributory factor.

Demyelinating Disease Symptoms

The signs and symptoms occurring in one type of demyelinating disease are different from those seen in another demyelinating condition. The common symptoms that can occur in patients with any of these disorders are mentioned below:

• Ataxia or Impaired muscle coordination
• Blurred double vision
• Blurriness in central visual field which affects one eye
• Clonus or convulsion
• Fatigue
• Dysarthria or speech disorder
• Hand paralysis
• Clumsiness
• Hemiparesis or paralysis of one side of the body
• Lack of coordination
• Paresthesia or tingling, twitching and burning sensations on the skin
• Ocular paralysis
• Neurological symptoms
• Loss of sensation
• Genital anesthesia
• Impaired vision
• Muscle weakness
• Spastic paraparesis (weakness in both legs)
• Hearing problems
• Incontinence
• Unsteady gait
• Migraine headache
• Seizures
• Vertigo
• Memory loss

Demyelinating Disease Prevention

Currently, there is no way to prevent these diseases from occurring as the etiology of demyelination of nerves often remains unknown. Following a proper diet rich in various vitamins, minerals and protein may reduce the risk of the disorders in some people. However, it cannot be prevented in individuals with genetic factors causing nerve demyelination. Researches are being carried out to find out whether it is possible to prevent nerve demyelination in such people.

Demyelinating Disease Diagnosis

Doctors use specific diagnostic criteria to determine whether an individual has demyelinated nerves. A thorough physical examination is useful for making this diagnosis while the doctor may also study the medical history of the patient. It is also important to consider the family history of a patient to find out if anyone had any of these CNS or PNS disorders. The following diagnostic procedures are used for this purpose:

Magnetic Resonance Imaging (MRI)

This medical imaging technique can be used for detecting these diseases. It allows a diagnostician to visualize the brain and nerves to diagnose the condition. Demyelinating conditons lead to changes in the brain water content which cause visible spots that can be detected on MRI images.

Evoked potential or evoked response

This electrical potential is recorded from nervous system after the presentation of some stimulus, as differentiated from spontaneous potentials that are detected by EEG (electroencephalography), EMG (electromyography) and other electrophysiological recording techniques.

CSF Analysis

Analyzing the cerebrospinal fluid is highly beneficial for diagnosing CNS infections. A CSF Culture test can help to identify the microorganism causing the infection.

Quantitative Proton Magnetic Resonance Spectroscopy (MRS)

This non-invasive analytical method is quite useful for studying the metabolic changes individuals with seizure disorders, Alzheimer’s disease and other brain conditions. It can be effectively used for observing whether the symptoms experienced by the patient are caused by nervous demyelination.

Lumbar Puncture

In this procedure, a hollow needle is inserted into the space in the lumbar region of the spine. A sample of cerebrospinal fluid is then collected, which is later examined for making the diagnosis.

Demyelinating Disease Differential Diagnosis

Diagnosing these disorders is fairly difficult as the symptoms displayed by patients can be caused by a number of other similar conditions. It is important for a diagnostician to rule out the following health problems while making the diagnosis:

• Transverse Myelitis
• Adrenoleukodystrophy
• Neuroborreliosis
• Neurological complications of AIDS
• Neurosyphilis
• Vascular diseases of CNS

Demyelinating Disease Treatment

Most types of demyelinating conditions are incurable, with treatment mainly focusing on the management of the symptoms and slowing the process of demyelination. Improving the quality of life of the patients is often the main object of the doctors. The treatment is generally patient-specific and depends on the specific disease and its stage of progression.

Treatment can involve:

• Medications
• Counseling
• Physical exercise
• Relaxation techniques
• Lifestyle changes
• Patient education

Sometimes, deep brain stimulation of the thalamus may also be necessary. The lifestyle changes usually recommended to the patients include certain dietary changes, giving up smoking and taking considerable amounts of rest every day.

The immune system of patients is greatly involved in bringing about the neurodegenerative changes occurring in progressive Multiple Sclerosis. At present, there are no treatment options that can fight these immune cells. Scientists are trying to understand the role of immunity in the condition so that they can find an effective treatment option that would address the immune cells.

Demyelinating Disease Prognosis

The outcome of treatment depends on what type of demyelinating disorder is present in the patient. Prognosis for some diseases depends on numerous factors, such as:

• Subtype of the condition
• Degree of disability caused by it
• Initial symptoms
• Age of the sufferer
• Sex of the sufferer

One-third of the people suffering from other demyelinating diseases like Central Pontine Myelinolysis recover after receiving treatment, while the remaining two thirds of the patients suffer from some degree of disability. Patients with conditions like Transverse Myelitis often begin to recover within two to twelve weeks after onset of the disease.

Demyelinating Disease Life Expectancy

All these conditions are not fatal and many of them can be cured completely when treated at an early stage. The life expectancy for individuals with Multiple Sclerosis is usually five to ten years lower than healthy people. However, some of the demyelinating disorders can be life threatening and can lead to the death of the patients within a few years if left untreated.

Demyelinating diseases are potentially dangerous and require early diagnosis along with prompt treatment. Individuals with this type of health problems can lead a reasonably normal life with proper management and follow-up care.