What is multiple sclerosis (MS)?

Updated: Feb 21, 2019
  • Author: Fiona Costello, MD, FRCP; Chief Editor: Hampton Roy, Sr, MD  more...
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Answer

Answer

MS is a CNS disorder that is characterized by both inflammatory and neurodegenerative mechanisms of brain and spinal cord injury. [1, 2] Consequently, most patients with MS tend to experience both episodic relapses and progressive neurological impairment throughout the disease course. Affecting more than 2 million people worldwide, MS is the leading cause of nontraumatic neurological disability in young adults. [2] The diagnosis of MS can be established based on clinical and radiological criteria in patients who experience two or more neurological events consistent with multifocal CNS inflammation that are disseminated in space (DIS) and disseminated in time (DIT). Since the publication of the original McDonald criteria [3] and subsequent iterations, [4, 5] radiological endpoints have played a critical role in the diagnosis of MS.

Most (85%) patients with MS begin their clinical disease course with episodes of neurological dysfunction (relapses), which are followed by complete or incomplete recovery. [1, 2] Over time, most patients with relapsing-remitting MS (RRMS) transition to secondary progressive multiple sclerosis (SPMS). Patients with SPMS present with features of worsening neurological disability with or without clinically overt relapses. [1, 2] Approximately 15% of patients with MS experience a primary progressive course from onset, either without preceding relapses (known as primary progressive multiple sclerosis [PPMS]) or with superimposed neurological events, known as progressive relapsing MS. [1, 2]


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