Misdiagnosis of multiple sclerosis: frequency, causes, effects, and prevention.

A diagnosis of multiple sclerosis is heavily influenced by clinical judgment. Misdiagnosis of multiple sclerosis is common and has important consequences for patients and the cost of healthcare. Although rigorous data about the frequency and causes of misdiagnosis are lacking, misinterpretation and misapplication of clinical and radiographic diagnostic criteria and terminology are likely important factors. Appropriate and stringent application of diagnostic criteria and continued vigilance for "red flags" suggesting alternative diagnoses are strategies critical for prevention of misdiagnosis.