Severe and extreme idiopathic median nerve lesions at the wrist: new insights into electrodiagnostic patterns and review of the literature.
BACKGROUND
We evaluated the electrodiagnostic (EDX) pattern of severe and extreme median nerve lesions at the wrist (MNLW) in patients with idiopathic carpal tunnel syndrome.


METHODS
EDX data were recorded in 229 patients with 314 severe and extreme MNLW and 447 patients with 777 non-severe MNLW. We recorded distal motor latency (DML) to abductor pollicis brevis (APB) and second lumbricalis (2L), sensory conduction (SC) from digits 2 and 3, and needle examination of APB.


RESULTS
Preservation rate of DML to APB and 2L and of SC from digits 2 and 3 were 100%, 100%, 85%, and 76%, respectively, for severe MNLW, and 37%, 90%, 36%, and 26% for extreme MNLW. Active denervation, as demonstrated by fibrillation potentials, was found in 1% of non-severe NMLW, 7% of severe MNLW, and 56% of extreme MNLW cases.


CONCLUSIONS
In idiopathic severe and extreme MNLW, the DML to the 2L and averaged SC from digit 2 can be present when other responses are absent.
Laboratoire d'électromyographie, Avenue Ledru Rollin, 75011, Paris, France.
Paul
P
Seror
Raphaéle
R
Seror
D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D004568:Electrodiagnosis; D005260:Female; D006801:Humans; D008297:Male; D020423:Median Neuropathy / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology*; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology*; D011930:Reaction Time; D012189:Retrospective Studies; D012720:Severity of Illness Index; D014953:Wrist / Q000294:innervation*
abductor pollicis brevis; body mass index; carpal tunnel syndrome; motor conduction; second lumbricalis; sensory conduction