Duration of symptomatology and median segment sensory latency in 993 carpal tunnel syndrome hands (668 cases)

RESUMO

According to median sensory nerve action potential onset-latency to index finger in a 140 mm fixed distance, 993 carpal tunnel syndrome (CTS) hands from 668 patients were grouped into MIld (3.0 to 3.5 ms, 384 hands), MOderate (3.6 to 4.4 ms, 332 hands), SEvere (>4.4 ms, 135 hands) and Unrecordable (142 hands) and correlated with CTS symptomatology duration. All patients have sensory antidromic median-radial latency difference (MRD) e = 1.0 ms without any doubt CTS diagnosis. Patients with systemic disease, trauma or previous surgery were excluded. There is a remarkable cumulative percentage increase from 1 to 12 months in group UN (3.5 per cent to 38.7 per cent, 11 folds), much less than the group MI (13.8 per cent to 54.6 per cent, 3.9 folds). There is also a remarkable non-cumulative percentage increase in group UN, from 1 to 4-12 months; the group MI had a relatively uniform distribution in all symptomatic duration groups from 1 to > 60 months. The conclusion is that median nerve compression at carpal tunnel can lead to unrecordable potentials in a relatively short period from 1 to 12 months of evolution, suggesting acute/subacute deterioration. Eletrophysiological evaluation must be done periodically in patients that underwent clinical treatment, since cumulative 38.7 per cent of group UN was found in 12 months period.