The ankle clonus test is not a clinically useful measure of spinal cord integrity in children

Abstract

Purpose: Bilateral flexion-induced ankle clonus has been proposed as a test of spinal cord integrity during anesthesia for scoliosis surgery. The purpose of this study was to establish the reliability of this test in normal children emerging from volatile anesthesia. A secondary objective was to determine if there was a difference in the validity of this test with either sevoflurane or isoflurane anesthesia. Methods: In a randomized, prospective blinded clinical trial, 32 healthy children aged three to 13 yr, were randomized to receive either isoflurane (Group 1, n = 15) or sevoflurane (Group S, n = 17) for maintenance of anesthesia during dental restorative surgery. During emergence, an observer, blinded to group allocation, recorded ankle clonus scores (number of beats to a maximum of 5 on each side) at 60-sec intervals until tracheal extubation. End-tidal anesthetic concentration was measured contemporaneously. Results: Non-sustained ankle clonus was elicited in a majority of children during emergence: 13 (87%) patients in Group 1 and 15 (88%) in Group S demonstrated at least non-sustained or unilateral clonus. However, bilateral sustained (> 5 beats·min-1) ankle clonus occurred in only four (27%) patients in Group 1 and four (24%) patients in Group S (P = 0.83). Conclusion: We conclude that the specificity of the ankle clonus test is too low to be clinically useful as a measure of spinal cord integrity in children, both when isoflurane and sevoflurane are used as the primary anesthetic agent.