Prediction of the neurophysiological diagnosis of carpal tunnel syndrome from the demographic and clinical data.

Objective: To use demographic and clinical data to identify the clinical pattern that best predicts the diagnosis of carpal tunnel syndrome (CTS), as defined by neurophysiologic studies.

Methods: A diagnostic cross-sectional study in 2535 consecutive patients (3907 upper limbs) older than 12 years old who were referred for nerve conduction studies in the upper limbs between August 2001 and January 2003 in 3 university hospitals and 2 private neurophysiology services in the state of Rio Grande do Sul, Brazil.

Results: A neurophysiologic diagnosis of CTS was established in 39.1% of these upper limbs. The presence of paresthesias or pain at least 2 of the first 4 digits in association with one of the following: female gender, symptoms worsening at night or on awakening, an BMI > or =30, thenar atrophy, or other sign (Tinel's, Phalen's, or Reversed Phalen's signs); were the best pattern associated with the diagnosis.

Conclusions: We have found that the clinical picture alone does not seem sufficient, in majority of the population, to correctly predict the diagnosis of CTS, as defined by median nerve neuropathy at the carpal tunnel. We believe that a compressive lesion of the median nerve at the carpal tunnel can be present both in patients with no typical symptoms of CTS (including asymptomatic individuals) and in patients in which neurophysiologic studies are negative.

Significance: Further studies separating patients into these groups will allow us to identify the long-term prognosis as well as the ideal therapeutic approach for each of these clinical situations.