Among the primary features of MS, CNS lesions have far reaching consequences. These are attributable to multiple sclerosis’ CNS demyelinating effect. MS is characterized by the demyelination and inflammation of the nerve cells. The resulting lesions can cause problems in different parts of the body because nervous tissue plays a part in regulating all the organs and organ systems in the patient’s body.
Technically speaking, the CNS or central nervous system constitutes the brain and the spinal cord, which are protected by the blood-brain barrier, skull and spine. (Some medical scientists define the CNS more expansively, adding to the basic definition above the retinas and cranial nerves.) In addition to the central nervous system there is a peripheral nervous system, which includes the nerves and ganglia (“relay points”) beyond the brain and spinal cord. The PNS connects the CNS to the organ systems and extremities of the body. Unlike the CNS, it has no special protective shields. Thus, it is especially vulnerable to injury. Together, the CNS and PNS carry signals from one part of the body to another. They make up a complex communication system.
The Progression of MS: CNS Lesions and their Impact
When MS strikes, it tends to affect the white matter of the CNS. This tissue is distinct for its high density of nerve fibers, which are covered in protective myelin sheaths. In MS, CNS lesions occur in the white matter 95% of the time. The white matter typically facilitates communication between different grey matter regions of the CNS, and also between the grey matter and other parts of the body. When it is damaged by the process known as demyelination, it is no longer possible for the affected nerves to transmit signals to the CNS and the rest of the body. It is possible for patients to consequently lose part or all of the function of the affected organs. Some of the MS symptoms that might result follow: muscle weakness, tingling, numbness, incontinence, spasticity, visual impairment, fatigue, and cognitive dysfunction.
While it is safe to say that most MS lesions occur in the white matter, the exact areas of white matter affected vary from person to person. In one patient with multiple sclerosis, CNS lesions may primarily affect the vision; in another patient, they may affect the person’s balance and gait. Additionally, some people may have very few symptoms, while others have many distinct symptoms. The progression of the disease is also unpredictable. It is because of this variation in presentation and progression that MS can be so tricky to diagnose.
