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Clinically Isolated Syndrome: Causes, Diagnosis, How are Clinically Isolated Syndrome and Multiple Sclerosis Different from Each Other?

What is Clinically Isolated Syndrome (CIS)?

Clinically isolated syndrome (CIS) is an episode of neurological symptoms that lasts for 24 hours and is associated with fever, infection, and other illnesses. It involves demyelination (loss of myelin, protective coating of the nerve cells) in the central nervous system.

Clinically isolated syndrome (CIS) is often categorized as a type of multiple sclerosis, as its first clinical episode. There are a few chances of a clinically isolated syndrome developing into multiple sclerosis.(1)

How are Clinically Isolated Syndrome and Multiple Sclerosis Different from Each Other?

The major difference is that Clinically isolated syndrome (CIS) is a single episode while multiple sclerosis involves multiple episodes or flare-ups.

Once occurred, there is no surety that Clinically isolated syndrome (CIS) will occur again. Multiple sclerosis is a lifelong illness with no cure. There can only be symptom management.

Conditions associated with Clinically isolated syndrome (CIS) include:

  • Optic Neuritis: It is a condition in which the optic nerve is damaged, which results in blind spots, double vision, and poor vision. There may also be eye pain.
  • Transverse Myelitis: A condition that involves damage to the spinal cord. There is muscle weakness, numbness, tingling, and bladder and bowel issues.
  • Lhermitte’s signs: It is also known as a barber chair phenomenon. It leads to a lesion on the upper part of the spinal cord. There is an electric shock-like feeling going from the back of the neck to the spinal column on bending the neck downward.

Clinically isolated syndrome (CIS) can lead to difficulty with balance and coordination, dizziness while walking, sexual dysfunction, muscle stiffness or spasticity, and difficulty in walking.

In both Clinically isolated syndrome (CIS) and multiple sclerosis there is damage to the myelin sheath. Symptoms depend on the location of the lesion.

It is difficult to differentiate between the two and can be detected through an MRI. If there is evidence of a single episode it is Clinically isolated syndrome (CIS). If multiple lesions and episodes are detected a person may have multiple sclerosis.

Causes of Clinically Isolated Syndrome

There is an inflammation and damage of the myelin sheath in Clinically isolated syndrome (CIS) that occurs anywhere in the central nervous system.

The exact cause is not clear, but there are certain risk factors associated with its occurrence.

  • Age: It can occur at any age, but, is more diagnosed in adults between ages 20 and 40 years.(1)
  • Gender: Clinically isolated syndrome (CIS) is more common in women than men.(1) Multiple sclerosis is also more common in women than men.

An episode of Clinically isolated syndrome (CIS) puts a person at risk of developing multiple sclerosis.

How to Diagnose Clinically Isolate Syndrome?

If any symptom of Clinically isolated syndrome (CIS) is noticed the physician refers the patient to a neurologist.

The neurologist takes a complete medical history and does an examination of:

  • Balance and coordination
  • Reflexes
  • Eye movement and basic vision

There are a few diagnostic tests that are advised, that include:

  • Blood Test: To confirm or rule out Clinically isolated syndrome (CIS) or multiple sclerosis
  • MRI: It is effective in detecting the lesion caused by demyelination. In it, a dye is injected into a vein that highlights the area of active inflammation. The dye helps determine if it is the first episode or if other episodes have also occurred.
  • Lumbar Puncture: It is done to analyze cerebrospinal fluid for protein markers.
  • Evoked Potentials: It is a measure of how the brain responds to sight, sound, or touch. A study shows 30% of people with CIS have abnormal results of evoked potential.(2)

Clinically Isolated Syndrome Progression to Multiple Sclerosis

It is not necessary every Clinically isolated syndrome progresses to multiple sclerosis.

If an MS-like brain lesion is detected in MRI there are 60-80 percent chances of having another flare-up and multiple sclerosis as a diagnosis in several years.(1)

If no MS-like brain lesion is detected the chances of developing multiple sclerosis is only 20%.

According to a report on the natural course of Clinically isolated syndrome:(3)

  • 48.1% of people with Clinically isolated syndrome developed relapsing-remitting multiple sclerosis within 10 years of an initial episode
  • 44.7% of people developed relapsing-remitting multiple sclerosis within 20 years
  • 14.9% developed secondary progressive multiple sclerosis within 10 years of an initial episode
  • 38.8% developed secondary progressive multiple sclerosis within 20 years

As a person has a second episode the doctor advises another MRI.

Treatment of Clinically Isolated Syndrome

A mild case of Clinically isolated syndrome clears up on its own within a period of few weeks.

In case of a serious symptom of optic neuritis, a high dose of steroid is given, which is either injected or given orally. Steroids hasten the recovery.

There are numerous disease-modifying drugs that are used in multiple sclerosis. They help reduce the severity and frequency of flare-ups.

They are numerous drugs that are approved for the treatment of Clinically isolated syndrome. It is good to speak with a neurologist about the benefits and risks of each before starting them.

Sheetal DeCaria, M.D.
Sheetal DeCaria, M.D.
Written, Edited or Reviewed By: Sheetal DeCaria, M.D. This article does not provide medical advice. See disclaimer
Last Modified On:April 18, 2021

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