Diagnostic Value of H reflex in the S1 radiculopathy

J Korean Assoc EMG Electrodiagn Med 1999;1(1):49-54.
Published online January 1, 1999.

Abstract

Objective : This study is designed to verify the most valuable parameter of H reflex to document S1 radiculopathy. Method : 53 patients of L5(33 patients) and S1(20 patients) radiculopathy(unilateral and unilevel) clearly defined by surgery or selective nerve root block as a gold standard of the diagnosis and 50 normal controls were included in the study. Sensitivities and specificities were delineated from the each diagnostic criteria of H reflec for S1 radiculopathy. Results : Sensitivity and specificity of unilaterally absent H reflex as a diagnostic criteria of S1 radiculopathy were 50%(10/20), 94%(31/33) respectively. The side-to-side difference of latency in maximal amplitude H reflex showd 50%(5/10) sensitivity and 100%(31/31) specificity for S1 radiculopathy among the patient who had H reflexes in both sides. Considering above 2 parameters delineated the diagnostic sensitivity and specificity for S1 radiculopathy to be 75%(15/20) and 94%(31/33). Amplitude ratio between side-to-side maximum H amplitudes and the H/M ratio difference of both sides revealed lower sensitivity and higher false positive rate. Needle EMG demonstrated 30%(6/20) sensitivity and 97%(32/33) specificity for S1 radiculopathy. 3%(2/33) of L5 radiculopathy showed unilateral absence of H reflex. Conclusion : H reflex study is more sensitive electrodiagnostic tool than the needle EMG in the diagnosing unilateral, unilevel S1 radiculopathy, and the diagnostic sensitivity of H reflex was highest when unilateral absence or the side-to-side differences longer than 1.61ms was used as a diagnostic criteria, but sometimes its abnormality was noted in unilateral, unilevel L5 radiculopathy.

Key Words: H reflex, S1 radiculopathy