Multiple sclerosis (MS) and Alzheimer’s disease (AD) are sometimes confused as the two disorders are characterised by the neurological deterioration of certain functions. Alzheimer’s disease and multiple sclerosis are both progressive, and both diseases have the potential to create severe disability in those that are affected. Although both MS and AD share those similarities, their treatments are quite different. Multiple sclerosis is an autoimmune disorder where an individual’s own immune response causes damage to the protective coating on the nerves. Due to this, MS is classified as a demyelinating disease, in which symptoms are related to damage incurred by parts of the central nervous system [1]. Alzheimer’s disease is not considered a demyelinating disease; however, demyelination is sometimes seen prior to the appearance of symptoms, most related to memory loss; the progression of the disease is not related to demyelination, as in MS. What is seen in Alzheimer’s disease is the progressive damage to the neurons in the brain itself [2].

Multiple sclerosis MS is a central nervous system disease where the immune system, which normally fights off invading organisms, attacks the body’s myelin sheaths. Myelin sheaths are the protective insulation that encases neurons and helps high-speed neuronal communication. Myelin assists and protects neurons, and without myelin, the brain and the spinal cord malfunction. To protect their integrity, neurons are wrapped in myelin (protective insulation). If there is damage to the myelin, individuals with MS experience weakness, neuropathic pain, and loss of coordination due to the irregular neural signaling. Individuals with MS may also experience paralysis when their neurons and myelin sheaths are damaged beyond repair [3].

Individuals with MS may experience a wide variety of symptoms depending on the extent and location of damage to the central nervous system. The most commonly reported symptoms are tingling and/or numbness, blurred vision, and loss of coordination. As the disease progresses, there will usually be a series of acute immune attacks, fatigue, spasticity, difficulty walking, and cognitive impairment. There are several approved disease-modifying treatments; however, none target the cognitive impairment that is seen in individuals with MS [3]. Dr. Friedrich von Frerichs is credited with citing cognitive impairment in MS for the first time in 1849, 25 years after the disease was already described. Even though it was recognized that MS disease did affect cognition, reports on cognitive impairment differed [4].

It was estimated that only two percent of patients reported blunted intellectual function in the late 19th and early 20th centuries [5]. It is believed that this was due to neurologists not asking about cognitive function or not having means of measuring cognitive function. In 2001, the Minimal Assessment of Cognitive Function in Multiple Sclerosis (MACIFMS) battery test was established. The MACFIMS is a 90-minute assessment of visuospatial ability, word fluency, learning, memory, processing, and executive function. With this test, it is now confirmed that cognitive impairment is linked with MS. Physicians now recognize that MS affects more than 2 million people worldwide, and 40 to 65 percent of these patients experience some form of cognitive impairment (Devere, 2011) [6]. The progression of MS is usually tracked using a standardized scale called the Expanded Disability Status Scale, or EDSS. This scale ranges from 0, which indicates no disability, to 10, which indicates death. Increments are scored at 0.5 as the disability evolves.

The EDSS assesses eight functional systems:

• Pyramidal: muscle weakness or trouble moving the limbs
• Visual: problems with vision
• Cerebellar: tremor, loss of balance, and coordination problems
• Brainstem: uncontrolled eye movements and difficulty talking or swallowing
• Sensory: numbness or unusual sensations
• Bowel and bladder: changes in gastrointestinal and urinary tract function
• Cerebral: difficulty with thinking or memory
• Other: any other neurologic finding attributed to MS

Similar to all neurological disorders, an individual with MS will go through three key stages: 1) investigation, 2) diagnosis, and 3) treatment management (Thompson et al., 1994). Multiple Sclerosis is a progressive and continuing disorder, and because of its nature, management can be an extensive and continually changing process. MS is divided into four stages, with all cases passing through each stage. Individuals are encouraged to self-manage in stages 1 and 2, but coordination with health care services is required in stages 3 and 4 (Thompson et al., 1994).

The four stages of multiple sclerosis:

• Initial (diagnosis)
• Early (little disability)
• Later (moderate disability)
• Advanced (severe disability)

Although overt dementia in Multiple Sclerosis is rare compared to other neurological disorders, such as Alzheimer’s disease, cognitive impairment in MS can have significant negative effects on daily living. A study of 426 MS patients found that 66% had difficulties recalling at least one task and 14% had difficulty making new memories, or "encoding." The difficulties with encoding could be attributed to decreased processing speed. The attention of MS patients is impaired, and tasks requiring sustained attention typically reveal mild to moderate impairment deficits [7]. In addition, an individual with MS may find difficulty remembering the information required to finish a task if there are other distractions present. Due to the central nervous system damage and the locations of the lesions in the brain in MS individuals, cognitive impairment is varied [7].

Cognitive impairment impacts the lives of individuals with MS and their families; up to three-quarters of those living with MS are unemployed within ten years of diagnosis. [8] The leading predictor of occupational disability for those that are diagnosed with MS is cognitive impairment, whereas physical disability, age, sex, and education contribute to less than 15 percent of employment. [9] Just as with Alzheimer’s, cognitive impairment due to MS places additional strain on the caregiver, who must help the patient combat intellectual, social, and occupational disabilities. In multiple sclerosis, there are four subtypes, defined by disease progression. The most common subtype is relapsing-remitting MS (RR-MS), which is the initial diagnosis in MS. In this subtype, individuals experience flare-ups of the disease system for a specified period, followed by a complete recovery or remission. Individuals diagnosed with RR-MS develop secondary progressive MS, which is defined as SP-MS, within ten to twenty years. With SP-MS, individuals will experience flare-ups or relapses of symptoms, but there is a steady increase in disease severity between relapses [3].

Primary progressive MS, or PP-MS, is the third subtype, in which the individual with MS experiences a steady increase in symptom severity from the onset of the disease. The final subtype is progressive-relapsing MS, or PR-MS; this subtype involves intermittent relapses occurring steadily during the progression of the disease. Individuals with progressive MS subtypes are more likely to also experience cognitive impairment in general. As with dementia, more research on cognitive decline and MS needs to be conducted. Individuals with early-onset MS are more likely to develop MS cognitive decline [3].

It is estimated that most cases of multiple sclerosis start with clinically isolated syndrome (CIS). Approximately 45% of cases report motor or sensory issues, 20% have optic neuritis, and 10% report symptoms associated with brainstem dysfunction. The remaining 25% have more than one of the previous issues [10]. The symptoms typically occur in two patterns: either as a flare-up or episodes that suddenly worsen, lasting a few days to months, followed by improvement, or worsening gradually over a period without recovery periods. [11] Just as Alzheimer’s disease has stages, it seems multiple sclerosis also does not follow a prescribed pattern. Individuals with MS could relapse, remit, and then become progressive later on. Relapses could occur without warning. Triggers, such as the common cold, gastroenteritis, and stress, are also known to increase the risk of a flare-up [12].

In summary, multiple sclerosis and the link to dementia need further research. The concern is that, in some cases, its rarity does not negate its prevalence. More research needs to be conducted, and assessment tools are required to indicate neurological decline for individuals with MS. Multiple sclerosis and its relationship to dementia should be investigated now that there is more conclusive research on dementia and other links to its development and progression.

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