Here I shall try to give you a broad overview of Multiple Sclerosis (MS). Multiple sclerosis is a demyelinating disease of the central nervous system (CNS). In the CNS, the axons are covered by myelin. The axon is the long slender projection of the nerve cell (neuron) that conduct's nerve impulses away from the body of the cell. The axons in the CNS are coated / covered with myelin, an electrically insulating layer made of phopholipids (a kind of fat). Schwann cells supply the myelin for peripheral neurons ( neurons outside the brain), whereas oligodendrocytes ( a type of cell found in the brain) supply myelin for axons of the CNS.
MS is characterized by demyelination of these axons, that is some process starts to destroy the myelin leading to loss of myelin. As the disease progresses even axons get destroyed.
Just what sets off this process is still not clear. Various infectious agents and environmental factors have been postulated but none conclusively linked to MS causation. As a disease MS is more common in Caucasians and more common as you head further from the equator both in the Northern and Southern hemisphere. Thus the incidence of disease is more in Ireland than say in Sub-Saharan Africa. Why you may ask and the answer is no one knows. Maybe it is an environment factor.
Fifteen years of age is the cut off. So if you were born in a country which has a low incidence of MS such as in Asia or Africa and then emigrate to a country with a higher incidence of MS such as Ireland or Canada after the age of 15, you shall carry that low risk of the country of birth with you but if you emigrated say around 6 years then your risks of developing MS go up to the risk of a native in Ireland or Canada.
MS is more common in women as compared to men but when it does occur in men it is usually more severe.
Clinical presenting features of MS-MS has been rightly called the great mimicker in neurology. It can present with a myriad of clinical signs and symptoms which are referrable to both the brain as well as the spinal cord. MS typically presents in the following ways:
1) Isolated attack of optic neuritis: the usual history is a young to middle aged woman who presents with sudden and rapid onset of loss of vision in one eye at times associated with pain on moving the eyes. This occurs due to demyelination of the optic nerve (the nerve which is involved in vision). If the attack remains confined to the optic nerve, this is referred to as a Clinically Isolated Syndrome (CIS). Not all patients with a CIS go on to develop MS, as there are other causes of optic neuritis besides MS.
2) Numbness or weakness in one part of the body.
3) Visual complaints like double vision (diplopia), eyes not moving well (weakness of a muscle of the eye).
4) problems with balance and coordination.
5) ataxia and tremors (patients have a prominent tremor in their hands or in their trunk, as well as are off balance while standing or walking). This is due to involvement of the cerebellum and cerebellar pathways by the MS demyelinating process.
6) problems with bladder control leading to urinary incontinence.
7) Weakness in the legs (paraplegia or paraparesis)--if MS involves the spinal cord, it may cause weakness of both the legs. This condition is referred to transverse myelitis or transverse myelopathy.
