False positive electrodiagnostic tests in carpal tunnel syndrome

Abstract

Of 50 normal subjects, 23 (46%) had at least one false positive electrodiagnostic test for carpal tunnel syndrome (CTS). There were 30% of the subjects who exhibited an abnormal median to ulnar sensory amplitude ratio of less than 1.1. In 7 subjects 8 extremities (14%) revealed prolonged residual latencies, and 4 extremities in 4 subjects (8%) had a difference of 0.4 msec between the median and ulnar palmar sensory latencies. The results of this study indicate that certain reported criteria for CTS are abnormal in a high percentage of normal subjects, thereby making them of limited value in the diagnosis of CTS. Of all the criteria studied, it appears that the comparison of the median to ulnar sensory latency across the carpal tunnel is of greatest potential value. However, even here a more conservative difference of 0.5 msec between median and ulnar nerves must be used to avoid false positive tests for CTS.

Influence of temperature on comparative nerve conduction techniques for carpal tunnel syndrome diagnosis

“…Fourt h , the CSI decreased significantly after cooling in c o nt rols, but did not increase significantly in patients with any loss electrodiagnosis accuracy. Fifth, as already emphasized 17 , we do not recommend using only one or even two latency differences for mild CTS electrodiagnosis and even using latency diff e rences, the temperature must keep above 32º C. We could not confirm that latencies between two n e rves in the same hand are less influenced by temperature as did Lew et al 15 . We believe that t h e re are no ideal human models that could re f l e c t exact limb temperature in NCS practice.…”

Early diagnosis of Carpal Tunnel Syndrome (CTS) in Indian patients by nerve conduction studies

“…The sensory and motor axons show a comparable incidence of abnormalities, in addition, often encountering selective involvement of motor fibres, with normal sensory conductions or vice versa 9 . Electrophysiological procedures have, however, become very sensitive that they can not only confirm the clinical diagnosis in most patients but also detect an incidental finding in some asymptomatic subjects 10 . The American Academy of Neurology has recently defined the standards, guidelines and options for electro-diagnostic studies of CTS based on a formal literature review 8 .…”

Management of chronic pain in whiplash injury

“…Many have queried their value as a diagnostic tool, finding no association between them and a patient's clinical status or satisfaction after surgery. [3][4][5][6] Therefore, we believe that they should be excluded from the diagnostic investigations of atypical carpal tunnel syndrome. While we accept that tertiary gain is a motive when treating patients with whiplash injury, we believe as indicated in the paper that some patients with chronic arm pain after a whiplash injury First, I wonder how they were able to obtain an exact zero degree slope cut with an extramedullary alignment system, since as they suggested, posterior slope and malrotation will influence the tibial position.…”