Multiple sclerosis (MS) is a chronic autoimmune disease that affects the central nervous system. The nervous system consists of the brain, spinal cord, and optic nerves. MS causes damage to the myelin sheath, which is the protective covering surrounding nerve fibers. This damage disrupts communication between the brain and other parts of the body, leading to various physical and cognitive symptoms.
What parts of the head and brain does MS affect?
MS can affect several parts of the head and brain, leading to a wide range of symptoms:
Eyes and vision
Since the optic nerve connects the eye to the brain, MS can cause various vision problems including:
- Blurred vision
- Partial vision loss or blindness in one eye (optic neuritis)
- Double vision (diplopia)
- Pain with eye movement
- Impaired color vision and contrast
These vision issues result from MS damaging the myelin covering the optic nerves. Inflammation and nerve damage disrupt signals from the eye to the brain, affecting vision.
Face
MS can sometimes cause facial pain or trigeminal neuralgia. This involves severe pain or electric-shock sensations on one side of the face. It happens when MS damages the trigeminal nerve which controls facial sensations and movements.
Mouth and swallowing
Around 30-40% of people with MS experience dysphagia – difficulty swallowing. This happens when MS damages parts of the brain that control swallowing including the:
- Brainstem
- Cerebellum
- Cranial nerves
Swallowing problems can lead to choking, food aspiration, and malnutrition.
Hearing
Hearing loss or tinnitus (ringing ears) can occur with MS if it damages auditory nerves. Impaired hearing results when signals from the ear to the brain are disrupted.
Smell and taste
Loss of smell (anosmia) or taste can happen if MS lesions form in the frontal lobe of the brain where smell and taste signals are processed.
Headaches
Many people with MS experience chronic migraine or tension-type headaches. MS brain lesions can directly trigger or exacerbate headaches. Headaches may also result from medication side effects.
How does MS impair cognitive functions and the brain?
MS can impair thinking, learning, memory, concentration, and other cognitive skills by damaging nerve fibers in the brain and disrupting messaging between brain regions. Common cognitive symptoms include:
Information processing
MS can slow information processing speed and working memory – the ability to temporarily store and manage information.
Executive function
Executive functions like reasoning, problem-solving, decision making, planning, and multi-tasking may be impaired.
Attention
Sustained attention, concentration, and divided attention can all be affected. This makes it hard to focus on tasks.
Processing speed
Reduced speed of cognitive processing is very common with MS. Thinking and responding becomes much slower.
Memory
Short and long-term memory problems are some of the most frequently reported cognitive symptoms:
- Forgetting recent information and events
- Worse recall of past memories
- Trouble learning and remembering new information (impaired episodic memory)
Word finding
Many patients struggle to think of common words when speaking or writing. This is known medically as anomia.
Emotional control
MS can make it harder to regulate emotions due to impaired signaling between brain regions. People may experience mood swings, irritability, euphoria, or inappropriate laughing/crying.
What tests diagnose MS cognitive problems?
Since cognitive symptoms are invisible, testing is needed to confirm and monitor any changes in thinking. Commonly used neuropsychological tests include:
| Test | What it measures |
|---|---|
| Symbol Digit Modalities Test | Information processing speed |
| Paced Auditory Serial Addition Test (PASAT) | Auditory information processing speed and flexibility, calculation ability |
| California Verbal Learning Test (CVLT) | Verbal learning, memory, recall |
| Brief Visuospatial Memory Test (BVMT) | Visual memory, learning |
| Selective Reminding Test | Verbal learning and memory |
| Wechsler Adult Intelligence Scale (WAIS) | Overall cognitive functioning including working memory, processing speed, verbal comprehension |
| Delis-Kaplan Executive Function System (D-KEFS) | High-level executive functions like problem-solving, planning, inhibition |
These tests identify any cognitive impairment a patient is experiencing compared to normative data for their age group. Repeating tests over time tracks cognitive changes associated with MS progression and treatment response.
What MS disease factors influence cognitive problems?
Research shows that several MS disease characteristics increase the risk of cognitive dysfunction:
Duration of disease
People living with MS for longer have more cumulative brain damage and greater cognitive decline.
Age of onset
Earlier age of MS onset is linked to faster progression of cognitive impairment.
Type of MS
Progressive MS causes more cognitive dysfunction than relapsing-remitting MS. However, cognitive problems can occur in all MS types.
Lesion number and location
More MS lesions and lesions in critical brain regions like the cortex, subcortical white matter, and limbic system increase cognitive dysfunction.
Brain atrophy
Greater loss of brain volume predicts worse cognitive problems.
Disability and disease activity
More physical disability and inflammatory disease activity are associated with poorer cognitive function.
Can MS cognitive impairment be treated?
While there is no cure for MS, several therapies aim to improve cognitive symptoms or slow further decline:
Disease modifying therapies
MS drugs like ocrelizumab, fingolimod, and natalizumab reduce disease activity which may protect the brain and cognition.
Cognitive rehabilitation
Exercises targeting memory, attention, executive functions, and processing speed may improve skills. Occupational therapy can also help adapt to cognitive changes.
Medications
Stimulant drugs like modafinil, amantadine, and amphetamines can enhance fatigue, attention, and wakefulness. Cholinesterase inhibitors may help memory.
Treating symptoms
Optimizing sleep, fatigue, depression, pain, and epilepsy can improve daily cognition and brain functioning.
Brain reserve
Cognitive leisure activities, social and physical activity, education, and mentally stimulating jobs increase resilience against MS cognitive effects.
What is the outlook for MS cognitive problems?
With optimal treatment, many people with MS have mild cognitive dysfunction that progresses slowly over decades without severely impacting daily activities. However, MS can cause significant cognitive impairment in some patients, especially those with progressive MS, early onset, and many brain lesions.
Cognitive symptoms are a major factor reducing quality of life in MS. Even mild issues like forgetfulness, fatigue, and slower thinking can significantly disrupt work, socializing, and independence. Monitoring cognition and promptly treating any changes are critical to maximize brain health with MS.