Electromyographic study of overuse syndromes in sign language interpreters

Sign language is the fourth most common language in the United States; this mode of communication involves sustained, repetitive use of the hand, wrist, and arm. Signers, therefore, are at risk of overuse disorders as carpal tunnel syndrome (CTS) and ulnar neuritis (UL). Using electrodiagnostic methods, the prevalence of hand nerve entrapments in signers was investigated. Thirty-three signers, six of whom were deaf, were compared to 21 age-matched controls (mean age = 31 and 29 years; respectively). Demographics were obtained by questionnaire. Physical examination and nerve conduction studies followed; 78 hands were examined. No significant mean differences in median motor or sensory latencies discriminated signers from controls. Although no signer's median SNAP latency was greater than 2 SDs from controls, some signers could be considered "abnormal" by other published criteria (eg, median/ulnar mid-palmer comparisons). Using these, 10 of 33 signers had mild abnormalities, five suggestive of CTS, three of UL, and two of both; of controls, two had CTS and two UL. The ratio of electrodiagnostic abnormalities did not differentiate the two groups (p > .05). Reports of hand and/or wrist pain were extremely high in interpreters (nondeaf signers) and were linked to EMG findings (p < .05). Deaf signers, even those with ED findings consistent with CTS, all reported no symptoms, possibly because their signing is less stressful or learned at an earlier age.