The Poser criteria were proposed in 1983 as an update to the Schumacher Criteria for diagnosing multiple sclerosis. They were developed to reflect the advances of detection techniques (MRI scans and spinal taps) that have helped neurologists to determine the existence of lesions and other paraclinical evidence.

The Poser criteria are:

• Clinically definite MS
• 2 attacks and clinical evidence of 2 separate lesions
• 2 attacks, clinical evidence of one and paraclinical evidence of another separate lesion

• Laboratory supported Definite MS
• 2 attacks, either clinical or paraclinical evidence of 1 lesion, and cerebrospinal fluid (CSF) immunologic abnormalities
• 1 attack, clinical evidence of 2 separate lesions & CSF abnormalities
• 1 attack, clinical evidence of 1 and paraclinical evidence of another separate lesion, and CSF abnormalities

• Clinically probable MS
• 2 attacks and clinical evidence of 1 lesion
• 1 attack and clinical evidence of 2 separate lesions
• 1 attack, clinical evidence of 1 lesion, and paraclinical evidence of another separate lesion

• Laboratory supported probable MS
• 2 attacks and CSF abnormalities

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