Inflammatory demyelinating diseases of the central nervous system
Inflammatory demyelinating disease of the central nervous system is a class of conditions that are a direct result of the myelin sheath becoming damaged or deteriorated. This damage leads to many neurological problems and deficits. Multiple sclerosis is the most common form of disease under this classification, but optic neuritis, neuromyelitis optica (or Devic’s disease), transverse myelitis, acute disseminated encephalomyelitis (ADEM), and adrenomyeloneuropathy (a type of adrenoleukodystrophy) are also classified within this category.
Definition & Facts
The central nervous system consists of the brain and spinal cord. It is comprised of a network of nerves. These nerves send and receive signals from every part of the body and then the brain processes them and sends a message back through the body causing it to react. These signals control both voluntary and involuntary movement and responses to stimuli.
Many of the nerves in the central nervous system are protected by a fatty sheath called myelin. When this myelin sheath becomes damaged or deteriorated it is called demyelination. Demyelination causes the messages between the nerves to slow or even stop altogether. Without the protective covering the nerves themselves become inflamed. Inflammation is the often painful swelling of an injured or infected part of the body.
Without protection, the nerves may also become damaged or deteriorate. The nerve signals become altered, and this causes impairment of both motor function and sensory function. Motor functions are the voluntary movements of the body. The sensory part of the nervous system controls vision, hearing, touch sensations, taste, smell, balance and movement. The immune system is responsible for finding and destroying threats within the body. Autoimmune disease induce the immune system to attack the body’s healthy cells as a foreign threat.
Symptoms & Complaints
Symptoms usually present equally on both sides of the body. Each patient can present with a varying set of complaints that is unique to them.
Demyelination can be extremely painful. The nerves can feel like they are burning. Patients may present with numbness or feel a tingling or prickling sensation. They usually suffer from chronic fatigue. There can be a loss of reflexes and coordination which may appear as clumsiness.
There can be weakness or paralysis of motor function especially in the limbs. Vision may begin to double (diplopia) or blur. There may even be a loss of vision altogether. Patients may report difficulties with memory.
Loss of bladder control and bowel movements is common. Blood pressure can be difficult to control in patients suffering from demyelinating diseases. This can lead to heart palpitations and dizziness. Some patients may experience problems with swallowing (dysphagia). Symptoms may progress at an even but gradual pace. A patient's condition may become more stable and then suddenly fall into relapse.
The specific causes of demyelination are not known. It is believed to be an autoimmune disorder. This is because the inflammation is generally caused by the immune system’s response to a perceived threat. This autoimmune response causes the body to attack the myelin and/or the cells responsible for its production and maintenance. This response can follow a viral infection or a vaccination in some people, especially those who have an overly sensitive immune system. It may also be caused by a metabolic disorder or a hereditary one. A loss of oxygen to the nerves or physical compression of them may cause the initial damage to the myelin sheath. It can even be caused by a toxin such as alcohol or some medications. It might be a result of liver damage or disease.
Diagnosis & Tests
Diagnosis can be difficult. Patients will present with of an array of symptoms. The doctor may use magnetic resonance imaging (MRI) scans to search for lesions or scarring in the brain and nerves. There may be notable enlargement or inflammation of the nerves.
A neurological examination will show that muscles have weakened and may have atrophied. Deep tendon reflexes will be impaired or nonexistent. Walking will be atypical due to deteriorated motor control.
There will be a noted impairment in the response to sensory stimuli. Electromyography is used to check for slow nerve conduction. A spinal tap or lumbar puncture may be performed to check for elevated proteins in the cerebrospinal fluid.
Treatment & Therapy
As the disease presents differently in each patient treatment can vary widely as well. Treatment focuses on managing the symptoms and decreasing the effects of them. These treatments may include physical therapy as well as medications. Many patients respond well to corticosteroids such as prednisone.
If steroid treatment alone is not enough, other medications may be prescribed. These can include medicines designed to decrease the frequency at which new lesions form. Medications like interferon beta-1a or glatiramer acetate which reduce the immune system’s response may also be used. Treatment with intravenous immunoglobulin may improve the immune system and deter it from attacking healthy cells. This treatment may need to be repeated at regular intervals.
Another option may be plasma exchange. For this procedure, blood is removed from the patient and the blood cells are separated from the plasma. The plasma is then replaced with another person’s plasma before the blood is transfused back into the patient. This treatment is also generally repeated at regular intervals. High doses of vitamin D may be used to reduce the body’s inflammatory responses.
Prevention & Prophylaxis
Avoiding the use of alcohol may prevent other forms of demyelination. Proper monitoring of medications known to cause toxicity is also important.