Multiple Sclerosis: An Overview

Focus On Multiple Sclerosis: Need Of The Hour

Multiple Sclerosis (abbreviated as MS, also known as disseminated sclerosis or encephalomyelitis disseminata) is a chronic, inflammatory and potentially debilitating disease that affects the Central Nervous System (CNS), which is made up brain and spinal cord of unknown etiology. Multiple sclerosis is widely believed to be an autoimmune disease, a condition in which one in which the body, through its immune system, launches a defensive attack against its own tissues.

Multiple sclerosis affects neurons, the cells of the brain and spinal cord that carry information, create thought and perception, and allow the brain to control the body. Surrounding and protecting these neurons is a fatty layer known as the myelin sheath, which helps neurons carry electrical signals. In multiple sclerosis, the body mistakenly directs antibodies and white blood cells against proteins in the myelin sheath, a fatty substance that insulates nerve fibers of the brain and spinal cord. This results in inflammation and injury to the sheath and ultimately to the nerves that it surrounds. The result may be multiple areas of scarring (sclerosis). The myelin is broken down in patches throughout the central nervous system and the damaged patches become scarred (this is where the name comes from - sclerosis meaning scars and multiple means many). Without the myelin coating, nerve messages cannot travel normally and they can become garbled or lost so that the instructions sent by the nervous system to different parts of the body are disrupted and subsequent axonal degeneration. Eventually, this damage can slow or block the nerve signals that control muscle coordination, strength, sensation and vision. This scarring causes symptoms which vary widely depending upon which signals are interrupted.

Multiple sclerosis is unpredictable and varies in severity. In some people, multiple sclerosis is a mild illness, but it can lead to permanent disability in others. Treatments can modify the course of the disease and relieve symptoms.

Clinical Manifestations:
The onset of MS may be insidious or sudden. Common presenting symptoms include monocular visual impairment with pain (optic neuritis), paresthesias, weakness, and impaired coordination (Table 1). The most common clinical signs and symptoms at presentation include sensory disturbance of the limbs , partial or complete visual loss , acute and subacute motor dysfunction of the limbs , diplopia and gait dysfunction

MS frequently is overlooked because initial symptoms resolve spontaneously in most patients. Relapses occur within months or years. In some patients, however, MS has a primary progressive course from onset.

TABLE 1: Common Symptoms and Signs of Multiple Sclerosis
Symptoms
Depression
Dizziness or vertigo
Fatigue
Heat sensitivity
Lhermitte's sign (electrical sensation down the spine on neck flexion)
Numbness, tingling, pain
Urinary bladder dysfunction
Visual impairment (monocular or diplopia)
Weakness
Signs
Action tremor
Decreased perception of pain, vibration, or position
Decreased strength
Hyperreflexia, spasticity, Babinski's sign
Impaired coordination and balance
Impaired visual acuity or red color perception with optic disc pallor and afferent pupillary defect; disconjugate eye movements
Nystagmus

These signs and symptoms may occur in isolation or in combination, and have to be present for a minimum of 24 hours to be considered a "clinical attack." As any anatomical location of the CNS may be affected, the clinical presentation of individuals with Multiple Sclerosis is extremely variable.

The course may be relapsing-remitting or progressive, severe or mild, and may involve the entire neuroaxis in a widespread fashion or predominantly affect spinal cord and optic nerves. Very little is known about the underlying cause of disease course variability in Multiple Sclerosis. Individuals can be stable for many months or years, while suddenly experiencing a devastating clinical attack. Currently, no biological markers can assist the clinician in predicting the clinical course and/or the accumulation of disability. Within families, the clinical course of Multiple Sclerosis among affected relatives can span the entire spectrum of possibilities — the clinical course does not run true to type in families .Clinical disease progression is assessed by recording the accumulation of neurological disability with valid methodological tools, including the expanded disability status scale (EDSS).

The Three Clinical Phenotypes Of Multiple Sclerosis:
The course of MS is difficult to predict, and the disease may at times either lie dormant or progress steadily. Several subtypes, or patterns of progression, have been described. Subtypes use the past course of the disease in an attempt to predict the future course. A person diagnosed with a particular subtype may, for unclear reasons, switch from one subtype to another over time. Subtypes a­­­re important not only for prognosis but also for therapeutic decisions. In 1996 the National Multiple Sclerosis Society standardized the following four subtype definitions

Relapsing-Remitting Multiple Sclerosis (RR-MS):
Initially, more than 80% of individuals with MS experience a relapsing-remitting disease course with defined clinical exacerbations of neurological symptoms, followed by complete or incomplete remission. This subtype is characterized by unpredictable attacks (relapses) followed by periods of months to years of relative quiet (remission) with no new signs of disease activity. Deficits suffered during the attacks may either resolve or may be permanent. When deficits always resolve between attacks, this is referred to as "benign" MS.
Approximately ten years after disease onset, an estimated 50% of individuals with RR-MS convert to a progressive clinical course called secondary progressive (SP) MS, which is no longer characterized by clinical attacks and remissions, but by insidious progression of clinical symptoms.

Secondary Progressive Multiple Sclerosis:
Secondary progressive describes around 80% of those with initial relapsing-remitting MS, who then begin to have neurologic decline between their acute attacks without any definite periods of remission. This decline may include new neurologic symptoms, worsening cognitive function, or other deficits. Secondary progressive is the most common type of MS and causes the greatest amount of disability.

Primary-Progressive Multiple Sclerosis (PP-MS):
Primary progressive describes the approximately 10% of individuals who never have remission after their initial MS symptoms. Decline occurs continuously without clear attacks. The primary progressive subtype tends to affect people who are older at disease onset.

Progressive Relapsing Multiple Sclerosis (PR-MS):
Progressive relapsing describes those individuals who, from the onset of their MS, have a steady neurologic decline but also suffer superimposed attacks. A significantly rarer form is progressive relapsing MS, which initially presents as PP-MS; however, during the course of the disease, these individuals develop true neurological exacerbations. Individuals with SP-MS who have clinical exacerbations followed by incomplete remission are included in this category.