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MS Terminology Clarified for the Layman

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MS terminology is an assortment of medical terms and their meanings as they pertain to multiple sclerosis.  Some of the terms are not specific for MS in that they also apply to some other disorders. Others relate exclusively to MS, but might not be defined or explained in verbal or written discussion that refers to them. Nevertheless, the purpose of this resource is to increase health literacy regarding this disorder. More specifically, is a tool to help patients and others obtain, comprehend and utilize printed and verbal information about MS.

Medical Terminology Pertaining to Multiple Sclerosis    


Clinically isolated syndrome (CIS) – Is a person’s first episode of neurologic symptoms resulting from inflammation and demyelination in one or more sites of the central nervous system (CNS). By definition, the symptoms must last at least 24 hours. An unexplained bout of optic neuritis is but one example. A person who experiences CIS might or might not go on to develop MS. The risk of MS following an event is high if one or MS terminologymore MRI-detected lesion accompanies the symptoms. The risk is low if an MRI scan performed at the time of the symptoms is negative.  

Demyelination – Damage to or destruction of the myelin sheathe which covers nerve axons.   Multiple sclerosis is the most common cause but there are other disorders that can also cause it. – Demyelinating – adj.  

Expanded disability status scale (EDSS) – Is a method of quantifying disability in an individual who has multiple sclerosis. Because Dr. John Kurtzke developed the scale it also bears the name Kurtzke Disability Status Scale. The scores range from 0 to 10. A score of 0 means a person has no disability and a normal neurological exam. A score of 10 indicates death from MS. Scores in between 1 and 10 refer to varying degrees of disability proportionate to the height of the score.  Experts that treat MS use this scale to gauge the progression of a person’s disease.  

Gadolinium enhancement – Is the making of T-2-weighted MS lesions on an MRI scan brighter and more distinct from surrounding brain tissue by injecting gadolinium at the time of the scan. 

Gadolinium enhancing lesion – Is a T-2 weighted lesion on MRI scan that becomes brighter and more distinct with the use of gadolinium contrast medium. It is an indicator of active disease or ongoing inflammation in the area. 

Gliosis – Is in excess of glial cells, particularly astrocytes, in an area of damage to the central nervous system. It is a sign of attempted or actual repair of the damaged area. It is a component of MS plaques.  

JC virus antibody test – Is a blood test which detects prior exposure to the JC virus. Its main use is to determine if a patient with MS has a high risk of developing PML if treated with natalizumab.   

JC virus (John Cunningham virus) – Is the virus that causes progressive multifocal leukoencephalopathy (PML). The virus is present in approximately 70% to 90% of humans. People usually contract it during childhood. But it remains dormant in kidneys and lymphoid tissue for life and does not cause any problem as long as the immune system is functioning normally. When the immune system is in a compromised state however, the virus can undergo activation. In its activated state it can cause PML.  Its presence does not mean that it absolutely will result in this bad outcome.  But it does increase the risk. Conditions that compromise the immune system like AIDS, the use of a particular drug to treat MS (natalizumab), or the use of immunosuppressive drugs to treat a host of conditions can cause activation of the virus and thus increase the risk of PML.  

McDonald diagnostic criteria for MS – Is a set of criteria for diagnosing MS. It specifies and demonstrates the dissemination of lesions in time and space.  

MS plaque – Is the typical lesion of latter and late-stage MS. The plaques are scattered throughout demyelinated areas of the brain and spinal cord. They are well-demarcated gray and pink areas quite distinct from the surrounding white matter. They consist of large numbers of macrophages, gliosis with scarring and a dearth of oligodendrocytes. They show up as T-2 weighted lesions on MRI scan.  Much or all of the prior inflammation might have subsided. But if not, plaques might enhance with gadolinium.   

Optic neuritis – Is inflammation of the optic nerve – the bundle of nerve fibers that participate in vision by sending signals from the back of the eye to the back of the brain. Common symptoms are eye pain and temporary visual loss. Some patients also report flashing lights. It is a common manifestation of multiple sclerosis. There are also other causes.    

Progressive multifocal leukoencephalopathy (PML) – Is a rare but severe and usually fatal demyelinating disease of the brain. It leads to destruction of white matter in several regions of the brain. It is the result of activation of the JC virus. The virus destroys myelin by first infecting and destroying oligodendrocytes – the cells that form myelin. It can occur as a complication of the use of a particular drug for treating MS. It can also be a consequence of other factors that compromise the immune system.  

Sclerosis – Is hardening of tissue. In the case of MS the hardened tissue is scar tissue in multiple areas of the central nervous system.  

T2-weighted lesions – Bright spots on the MRI scan of a person with MS. They represent areas of damaged or destroyed myelin.


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Signs and Symptoms of MS Analyzed and Categorized

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