title: Three-dimensional vector graphing of the H reflex.
abstract: Comparison of latencies of the H reflex from side-to-side is considered a valid indicator of pathology, but amplitudes are too variable to allow similar comparison. Three pairs of electrodes were placed circumferentially and longitudinally along the calf to record the H reflex in three axes simultaneously. An H reflex with the greatest amplitude was produced by incrementally increasing submaximal stimulation to the tibial nerve. Three-dimensional vector graphs were constructed at three levels in each calf in ten normal individuals. Best fit curve Procrustes statistical analysis showed an average of 82.2 to 90.6% agreement of 3-D shape left-to-right with greater agreement at distal levels. Standard deviation ranged from 11.3% proximally to 8.2% distally. This represents much closer agreement than established norms for amplitude, which can vary from two to four times side-to-side. Three-dimensional vector analysis holds promise to further understanding of peripheral and central electrophysiologic phenomena.
authors.affiliation: Department of PM&R, The Ohio State University Medical Center, Columbus, Ohio 43201, USA.
authors.forename: C E
authors.initials: CE
authors.lastname: Levy
authors.forename: T
authors.initials: T
authors.lastname: Nishida
authors.forename: P
authors.initials: P
authors.lastname: Speckman
authors.forename: G
authors.initials: G
authors.lastname: Barkov
authors.forename: J C
authors.initials: JC
authors.lastname: Johnson
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D005260:Female; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D007866:Leg / Q000294:innervation; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009482:Neurophysiology / Q000379:methods; D011930:Reaction Time; D012107:Research Design; D013979:Tibial Nerve / Q000502:physiology