The tendon reflexes in the electrodiagnosis of sciatica.

In order to determine the diagnostic value of the electromyographically tested tendon reflexes (ETR) in lumbosacral radiculopathies, we compared the latency and amplitude of the knee (EKTR) and Achilles tendon reflex (EATR) to their clinical testing and to the EMG and H reflex values in 200 non selected patients (126 men, 74 women) aged 24-68 years (48.6 +/- 9.4). The control group was composed of 50 healthy volunteers (28 men, 22 women) aged 25-60 yrs (44 +/- 8.5). The combined electrophysiological reflex examination was abnormal in 45% of the affected limbs, being the most frequent pathological finding. EMG was abnormal in 34.4% and H reflex in 30.4% of the affected limbs. Furthermore, the EATR taken separately was more sensitive than the H-reflex (42.8% versus 30.4%). Pathological ETR were elicited in a considerable percentage of the clinically normal tendon reflexes (TR): 7.3% of the knee and 14.1% of the Achilles TR. On the other hand 65% of the clinically absent ATR were recorded electrically producing abnormally low and delayed muscle evoked potentials.