Skip to navigation Skip to content

Clinically Isolated Syndrome



Clinically isolated syndrome (CIS) is a term that describes a first clinical episode of a disease that shows characteristics of inflammatory demyelination that could be MS but has yet to fulfill criteria of dissemination in time (Lublin et al., 2014). It usually occurs in young adults and affects optic nerves, the brainstem, or the spinal cord. Although patients usually recover from their presenting episode, CIS is often the first manifestation of MS.

The most common CIS presentations and risk factors for Clinically Definite MS (Brownlee and Miller, 2014) include:

Optic Neuritis

  • Unilateral reduced visual acuity
  • Orbital pain particularly with eye movement
  • Reduced color vision
  • Afferent pupillary defect
  • Retrobulbar or mild disc swelling


  • Bilateral internuclear ophthalmoplegia
  • Ataxia and gaze evoked nystagmus
  • 6th nerve palsy
  • Multi-focal symptoms
  • Facial sensory loss
  • Vertigo
  • Ataxia
  • Dysarthria

Spinal cord

  • Incomplete transverse myelitis
  • Positive Lhermitte’s sign
  • Sphincter symptoms
  • Asymmetric limb weakness
  • Symptom progression between 4 hours and 21 days.

Risk factors

The important risk factors for the conversion to clinically definite MS (CDMS) are:

Treatment of CIS


Become a Research Champion

An MS Research Revolution

Support MS Research

Understanding and ending MS can’t come fast enough – it will take all of us working together. It’s easy to be a champion for MS Research – join us and proudly let everyone know that you’re helping to lead the MS Research Revolution.

Become a Research Champion

Become a Research Champion
© 2023 The National Multiple Sclerosis Society is a tax exempt 501(c)3 nonprofit organization. Its Identification Number (EIN) is 13-5661935.