Being diagnosed with MS can be overwhelming. However as with many other conditions, the disease can be managed to some degree by understanding what causes the symptoms.
Multiple sclerosis (MS) is an auto-immune disease affecting the central nervous system. What that means is that instead of protecting the body, the immune system starts to attack it by destroying the myelin sheath – a protective layer around the neurons in the brain and the spinal cord. This leaves the nerves unprotected, impedes their function and, as damage accumulates, eventually leads to neuron death. Depending on the location of the neuronal damage, MS is characterized by a variable experience of the disease that can cause problems with bodily functions, movement, and cognition.
MS is estimated to affect around 30 in 100,000 people, although the rate tends to be higher in countries with less sunlight that are further away from the equator. MS is 2.4 times more common in women than in men, and is typically diagnosed at around age 40. However rare, MS sometimes can also occur in teenagers and children. On average, patients with MS tend to have six to seven years shorter life expectancy than the general population.
These are attributed to genetics as well as multiple environmental factors, such as geographical latitude, sunlight exposure, vitamin D deficiency and certain viruses. A recent study at the Harvard T. H. Chan School of Public Health identifies Epstein-Barr, a common type of herpes virus, as a potential trigger for the auto-immune system to turn on neurons. However, no single cause appears to be solely responsible for the development of MS, which is likely instead to arise from a complex interaction of all the factors outlined above.
Diagnosis: Pathology and Symptoms
Doctors diagnose MS following the guidelines of the revised McDonald Criteria that involves clinical examination of the disease’s pathology and symptoms.
MS pathology can be seen on Magnetic Resonance Imaging (MRI) images as white spots representing inflammatory white matter lesions, which tend to appear around the ventricles, brain stem, cerebellum, and spinal cord.
However, the distribution and rate of acquiring lesions varies by person. On occasions when there is diagnostic uncertainty about the rate of MS activity, your doctor may suggest repeating MRI after several months to provide evidence that the disease is active and the lesions are separated in time.
While MS is traditionally considered an inflammatory white matter disease, degeneration of gray matter is increasingly recognized as a primary contributor to progressive cognitive decline and can occur independently. Besides MRI, your clinician can also check your cerebrospinal fluid for markers of auto-immune activity. They demonstrate that MS symptoms are being caused by the immune system attacking neurons and destroying their protective myelin sheath.
MS can have many symptoms. These tend to appear suddenly over the course of several days, typically lasting for short periods of time (from a few days to a few months), until complete or at least partial recovery, after which a patient can remain symptom-free for months or years. These spontaneous attacks are defined as relapses and the recoveries as remissions. Each new relapse results from an attack on the white matter of the central nervous system and, depending on its location in the brain or spinal cord, can cause very different symptoms. During a relapse you may experience new symptoms, or an increase in existing ones.
The most common MS physical symptoms are:
- problems with balance or walking
- blindness or disrupted vision
- difficulties swallowing and speaking
- bladder and bowel problems
- sexual dysfunction
- sensory changes and heat sensitivity
Around half of MS patients experience cognitive symptoms as well. These typically involve problems with attention, memory and thinking, depression or difficulties controlling emotions. In MS cognitive dysfunction is probably the most important determinant of employment status and tends to interfere with everyday tasks, such as driving, taking care of oneself and one’s home, social activity, physical independence, rehabilitation, and mental health.
It is hard to predict which MS symptoms one may develop. The disease is heterogeneous, causing patients to suffer from a highly idiosyncratic mixture of symptoms of varying accumulation and severity.
In the first instance, MS symptoms usually manifest as a series of relapses followed by near-complete recovery, but over time the neurological difficulties tend to worsen and accumulate.
Due to the heterogeneity and individual variation of symptoms, in clinical practice patients are grouped according to their MS sub-type. Nowadays MS is most often classified into relapsing-remitting (RRMS), secondary-progressive (SPMS), and primary progressive (PPMS).
How a patient’s MS begins and progresses is extremely variable and mostly unpredictable. The majority of patients (around 80%) start with RRMS, in which they experience a pattern of relapses from which they essentially recover (remissions), with relative stability between attacks. Few patients with RRMS do extremely well, with very few symptoms and little deterioration, but after a while the majority (around 60%) of people with RRMS start accumulating neurological problems progressively, either with or without occasional relapses. This sub-type of MS is termed SPMS.
Moreover, there is another subgroup of patients (around 15%) who develop PPMS. This type of MS is defined by continuous worsening of symptoms and progressing disability without distinct relapses. The onset of PPMS typically occurs at around age 40, which is later than the start of RRMS, but around the same age as the transition from RRMS to SPMS. On occasions, PPMS progresses very rapidly, reducing a patient to helpless dependency or death soon after onset.
Another rarer type of the disease exists, progressive-relapsing MS (PRMS). This is characterized by a steadily progressing disease from the outset, punctuated by occasional relapses. People with this form of MS may or may not experience some recovery following these attacks; the disease continues to progress without remissions.
Another term commonly used in MS staging is the clinically isolated syndrome (CIS). You may be diagnosed with CIS if you show MS pathology, but experience symptoms only once and subsequently remain symptom-free.
However, PRMS and CIS are much less common and most patients get diagnoses of RRMS, SPMS or PPMS.
- MS is an auto-immune disease affecting the central nervous system.
- It is 2.4 times more common in women than in men and is typically diagnosed at around age 40.
- MS is most likely caused by a complex interaction of genetics and environmental factors, such as geographical latitude, sunlight exposure, vitamin D deficiency, and certain viruses.
- Doctors diagnose MS by examining MS pathology and symptoms.
- MS is heterogeneous, causing the patients to suffer from an idiosyncratic mixture of physical and cognitive symptoms.
- MS symptoms often appear suddenly, lasting for days or months.
- Most patients are diagnosed with relapsing-remitting MS, which later progresses to secondary-progressive MS. Their disease is characterized by relapses and remissions.
- Around 15% of patients showing steady disease progression from the outset are diagnosed with primary progressive MS.