title: Normal limits of side-to-side H-reflex amplitude variability.
abstract: Our hypothesis was that side-to-side difference in the tibial H-reflex amplitude can aid in the diagnosis of unilateral S1 radiculopathy with an otherwise normal side-to-side H-reflex latency difference. We studied 47 healthy subjects, (mean +/- SD, 35 +/- 10 years) using methods similar to those described by Braddom and Johnson. Only those with side-to-side latency difference less than 1.5 msec were included (n = 45). Current was increased in 0.5 to 1.0 mA increments until the H-reflex amplitude maximized and then fell; on each side the response with the maximal peak-to-peak amplitude was measured for peak-to-peak amplitude and onset latency. The amplitude on the side of the smaller response was expressed as a ratio of the contralateral amplitude; this mean value (+/- SD) was 0.74 +/- 0.17. We conclude that a side-to-side amplitude ratio smaller than 0.4 (mean - 2 SD) in the face of a normal side-to-side latency difference is probably abnormal.
authors.affiliation: Department of Rehabilitation Medicine, University of Washington, Seattle 98195.
authors.forename: W R
authors.initials: WR
authors.lastname: Jankus
authors.forename: L R
authors.initials: LR
authors.lastname: Robinson
authors.forename: J W
authors.initials: JW
authors.lastname: Little
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D005260:Female; D006801:Humans; D008875:Middle Aged; D017933:Peripheral Nervous System / Q000502:physiology*; D010523:Peripheral Nervous System Diseases / Q000175:diagnosis / Q000503:physiopathology; D011930:Reaction Time; D012016:Reference Values; D012018:Reflex / Q000502:physiology*; D013977:Tibia / Q000294:innervation*