title: Sural sensory nerve action potential: A study in healthy Indian subjects.
abstract: BACKGROUND
  The sural sensory nerve action potential (SNAP) is an important electrodiagnostic study for suspected peripheral neuropathies. Incorrect technique and unavailability of reference data can lead to erroneous conclusions.
  
  
  OBJECTIVE
  To establish reference data for sural SNAP in age-stratified healthy subjects at three sites of stimulation.
  
  
  METHODS
  A prospective study was conducted in 146 nerves from healthy subjects aged between 18 years and 90 years, stratified into six age groups (a = 18-30 years, b = 31-40 years, c = 41-50 years, d = 51-60 years, e = 61-70 years, and f >71 years). Sural SNAP was recorded antidromically, stimulating at three sites at distances of 14 cm, 12 cm, and 10 cm from the recording electrode. Mean - 2 standard deviation (SD) of the transformed data was used to generate reference values for amplitudes. Analysis of variance (ANOVA) test was used for inter-group and between three sites comparisons of amplitudes.
  
  
  RESULTS
  The lower limits of amplitude at 14 cm were 12.4 μV, 10.4 μV, 6.5 μV, 5.3 μV, 2.9 μV, and 1.9 μV; at 12 cm were 13.5 μV, 13.6 μV, 8.5 μV, 7.8 μV, 3.5 μV, and 2.8 μV; and at 10 cm were 16.3 μV, 16.3 μV, 11.1 μV, 10.0 μV, 4.8 μV, and 3.7 μV for groups a, b, c, d, e, and f, respectively. A statistically significant difference in amplitudes was noted from the three different sites of stimulation (P < 0.001). The amplitude differed significantly above the age of 60 years (P < 0.01) but not between groups e and f (P > 0.05).
  
  
  CONCLUSIONS
  This study provides reference data for sural SNAP in Indian population at three different sites of stimulation along the calf in six age groups. It also shows significant variation in amplitude from the three different sites of stimulation.
authors: Department of Neurophysiology (EMG and EP), Bombay Hospital and Medical Research Centre, Mumbai, Maharashtra, India.
authors: Aarthika
authors: A
authors: Sreenivasan
authors: Department of Neurophysiology (EMG and EP), Bombay Hospital and Medical Research Centre, Mumbai, Maharashtra, India.
authors: Khushnuma A
authors: KA
authors: Mansukhani
authors: Department of Neurophysiology (EMG and EP), Bombay Hospital and Medical Research Centre, Mumbai, Maharashtra, India.
authors: Alika
authors: A
authors: Sharma
authors: Department of Neurophysiology (EMG and EP), Bombay Hospital and Medical Research Centre, Mumbai, Maharashtra, India.
authors: Lajita
authors: L
authors: Balakrishnan
keywords: Age; Indian; amplitude; reference values; stimulation site; sural