Demyelination: Demyelinating diseases and symptoms
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Multiple sclerosis (MS) is a disorder in which the immune system erroneously launches an inflammatory attack that damages healthy parts of the brain and/or spinal cord. Specifically, MS is caused by an autoimmune attack against the myelin sheath that protects nerves, which results in inflammatory demyelination.
What is demyelination?
The myelin sheath is a fatty covering around nerve fibers that helps them to send electrical signals more efficiently. Demyelination refers to the destruction and loss of this sheath, which leads to the development of lesions, where the tissue is damaged and scarred. A lesion also may be called a scar or plaque.
When myelin is damaged, nerves cannot send electrical signals as effectively, ultimately resulting in neurological problems that give rise to MS symptoms. The specific symptoms resulting from demyelination depend on exactly which nerve cells are affected.
For example, demyelination affecting the optic nerves — which carry information from the eyeballs to visual processing centers in the brain — tend to result in symptoms affecting the eyes and vision.
In turn, demyelination in the spinal cord is more commonly associated with symptoms like motor problems, unusual sensations referred to as dysesthesias, and trouble with bladder/bowel regulation.
Demyelination in the brain, meanwhile, can cause an array of symptoms from cognitive impairment to coordination difficulties, contingent on the specific brain region(s) affected.
Symptoms of demyelinating diseases
Depending on which nerves are affected, demyelination can result in a wide range of symptoms, including visual problems, motor disturbances, unusual sensations, mood and cognitive issues, and problems regulating the bladder and bowels.
Visual
- blurry vision and/or double vision (diplopia)
- loss of vision, usually in just one eye
- involuntary eye movements (nystagmus or internuclear ophthalmoplegia)
- vision that appears to shake or oscillate (oscillopsia)
- slowness by the eye’s pupil in adapting in response to shifts in lighting (afferent pupillary defect )
Motor
- muscle weakness
- reduced muscle control (ataxia)
- spasticity
- trouble walking or unusual walking patterns
- difficulty with balance and/or coordination
- dizziness or vertigo
- overactive reflexes (hyperreflexia)
- tremor
Sensory issues
- unexplained pain, or unusual pain in response to things that normally are not painful (allodynia)
- numbness
- tingling, stinging, itching, or prickling sensations (paresthesia and dysesthesia)
- the sensation of an electric shock passing through the body (Lhermitte’s sign)
- facial pain linked to damage to the trigeminal nerve (trigeminal neuralgia)
Cognitive and mood problems
- depression
- persistent, unexplained fatigue
- irritability
- anxiety
- impaired memory
- difficulty learning new things
- trouble concentrating or making decisions in day-to-day life
Genitourinary system
- urgent or frequent urination
- difficulty in starting urination
- an inability to hold in urine (incontinence)
- frequent urinary tract infections or UTIs
- constipation
- erectile dysfunction or vaginal dryness
- reduced sensation or pain in the genitals during intercourse (dyspareunia)
- difficulty reaching orgasm (anorgasmia)
Does demyelination always mean MS?
MS is the most common demyelinating disorder that affects the central nervous system (CNS), comprised of the brain, spinal cord, and optic nerves. It is not the only condition characterized by CNS demyelination, however.
Furthermore, other disorders are characterized by demyelination outside of the brain and spinal cord. In such conditions, which include Guillain-Barré syndrome, demyelination affects the peripheral nerves — those in the peripheral nervous system, or PNS. These nerves provide a communication network between the CNS and other parts of the body.
Differentiating between these conditions generally involves a thorough review of an individual’s medical history, coupled with an MRI imaging scan and other assessments to determine the exact patterns of demyelination.
What are the most common demyelinating diseases?
| Most common demyelinating diseases | Affected area |
|---|---|
| Multiple sclerosis | Central nervous system (brain, spinal cord, optic nerves) |
| Transverse myelitis | Spinal cord |
| ADEM | Central nervous system (mainly brain and spinal cord, occasionally also the optic nerves) |
| Optic neuritis | Optic nerves |
| Neuromyelitis optica | Mainly optic nerves and spinal cord |
| Guillain-Barré syndrome | Peripheral nervous system |
| Charcot-Marie-Tooth disease | Primarily the peripheral nervous system |
| Adrenoleukodystrophy | Both central and peripheral nervous systems |
Multiple sclerosis
MS is the most common disorder that causes demyelination in the central nervous system. Demyelination in MS results from an inflammatory attack accidentally launched by the immune system.
Depending on exactly which parts of the nervous system are affected, this damage can lead to a range of symptoms. These include muscle spasms, spasticity, fatigue, depression, unusual sensations, coordination issues, vision problems, and trouble regulating the bladder and bowels.
Transverse myelitis
A condition called transverse myelitis occurs due to inflammation and myelin damage in the spinal cord, which interrupts the nerve signals being sent throughout the body. It typically results in symptoms such as pain, muscle weakness, abnormal sensations, and/or trouble regulating the bladder and bowels.
Sometimes, transverse myelitis can occur as a manifestation of MS or other autoimmune disorders. This type of inflammation also may result from a bacterial infection or a viral infection (viral demyelination).
Acute disseminated encephalomyelitis (ADEM)
Acute disseminated encephalomyelitis (ADEM) is a brief but severe bout of inflammation that causes demyelinating damage in the brain and spinal cord, and occasionally also in the optic nerve. It usually develops following an infection.
Symptoms of ADEM are often similar to those of MS, but while MS is a chronic disorder in which damage accumulates over time, people with ADEM usually experience just a single attack.
Optic neuritis
Inflammation that causes damage to and demyelination of the optic nerves is known as optic neuritis. It can lead to visual problems, including lost or reduced vision, as well as aching pain with eye movement.
Optic neuritis may occur due to MS — often as the first sign of the disease. It is estimated that about 70% of MS patients experience optic neuritis at some point. This type of inflammation also may result from other autoimmune disorders or infections.
Neuromyelitis optica
Neuromyelitis optica spectrum disorder, or NMOSD, is a rare autoimmune demyelinating disorder that mainly affects the optic nerves and spinal cord. Symptoms can include vision problems, muscle spasms, limb weakness, and difficulty controlling the bladder and bowels.
This disorder is differentiated from MS because the two diseases tend to affect different parts of the nervous system. NMOSD is characteristically associated with specific self-targeting antibodies that drive the inflammatory attack against the nervous system.
Guillain-Barré syndrome
Guillain-Barré syndrome is an acute inflammatory disorder that causes damage to nerves in the peripheral nervous system — those outside of the brain and spinal cord. It usually develops in the weeks following an infection, particularly digestive or respiratory infections. Common symptoms include weakness, unusual sensations like tingling or prickling in the hands and feet, pain, and facial paralysis.
Charcot-Marie-Tooth disease
A group of genetic disorders called Charcot-Marie-Tooth disease (CMT) result in damage to myelin and nerve fibers in the peripheral nervous system, outside the brain and spinal cord.
Mutations in more than 40 genes have been linked to various types of CMT. Common symptoms of the disease include muscle weakness and sensory abnormalities.
Adrenoleukodystrophy
Adrenoleukodystrophy is a genetic disorder in which the body is unable to break down certain fat molecules. They thus build up to toxic levels in the nervous system and cause damage to myelin.
There are several forms of the disease, the most common of which are associated with mutations on the X chromosome, which means they mainly affect males. Symptoms vary by disease subtype, and may include muscle stiffness or weakness, nausea and vomiting, movement difficulties, and neurologic abnormalities.
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FAQs about demyelination and MS
Multiple sclerosis (MS) is the most common condition that causes demyelination in the central nervous system (CNS — the brain, spinal cord, and optic nerves). However, other conditions also may cause demyelination in the CNS or elsewhere in the body, namely in the peripheral nervous system. Differentiating MS from these other conditions generally involves a review of a patient’s medical history alongside clinical assessments to determine exactly which parts of the nervous system are being affected by myelin loss. There is no one specific test for determining the exact cause of multiple sclerosis.
Some demyelinating disorders, such as acute forms of ADEM (short for acute disseminated encephalomyelitis), can be fatal, although this is a rare occurrence. Other diseases that cause demyelination, including MS, are not life-limiting themselves, though they can increase the risk of complications like pneumonia that may potentially shorten the lifespan of patients.
When myelin is damaged or destroyed, it can be repaired and replaced by the action of specialized cells — namely by oligodendrocytes in the central nervous system, and Schwann cells in the peripheral nervous system — in a process called myelination. However, in MS and many other demyelinating disorders, such myelin repair is not a very efficient process. Thus, finding ways to improve myelin repair is an area of active ongoing research.
When a person decides to move, electrical signals are sent through nerves from the brain, down through the spine, and out to muscle cells, prompting a muscle or group of muscles to contract. Demyelination of nerve fibers can reduce the speed and efficiency of these electrical nerve impulses, dampening the signal that tells the muscle to contract and ultimately resulting in muscle weakness.
Pain is a common symptom of demyelinating disorders. Pain that results from damage to nerve cells, as through demyelination, is called neuropathic pain. Because demyelination interferes with the electrical activity of neurons, pain signals might be sent when they ordinarily would not be. This can be caused by electrical impulses that may be abnormal and/or due to nerve cells that might become overstimulated and misfire signals. Patients with multiple sclerosis, in particular, often experience several types of pain. This includes not only neuropathic pain but also musculoskeletal pain — pain that results from muscle weakness, stiffness, and/or other mobility issues.
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