The relationship between sensory latency and amplitude.
OBJECTIVE
To prove that the relationship between sensory latencies and amplitudes is useful in determining the severity of neuropathies. This is achieved by deriving a mathematical relationship between sensory distal latency and amplitude. Determine whether sensory amplitudes below predicted correlate with a worse pathology.


METHODS
Patients seen for Nerve Conduction Studies by the Department of Physical Medicine and Rehabilitation at Cooper University Hospital between 12/1/12 and 12/31/14 were invited to participate in a prospective database. The median, ulnar and sural sensory latencies and amplitudes were analyzed with both linear and power regression. Patients with amplitudes above and below the regression curve were compared for latency, amplitude and velocity of other nerves. Carpal Tunnel Patients were analyzed to determine whether Median sensory amplitude below predicted correlated with more severe disease.


RESULTS
For the Median nerve, Power Regression Analysis showed a stronger correlation (R2=0.54) than linear regression (R2=0.34). Patients with Median sensory amplitude below the power correlation curve showed significantly longer ulnar sensory latency, and lower sensory amplitude than those above. Carpal Tunnel Syndrome patients with Median sensory amplitude well below predicted by the power relationship showed more advanced disease. For the ulnar and sural sensory nerve, the difference between power and linear regression was not significant.


CONCLUSIONS
A power regression curve correlates sensory latency and amplitude better than linear regression. The latency amplitude relationship correlates with other parameters of nerve function and severity of Carpal Tunnel Syndrome. This implies that below predicted sensory amplitude may indicate worse disease, and could be a useful diagnostic tool.
Cooper Medical School of Rowan University, United States. Electronic address: Bodofsky-elliot@cooperhealth.edu.
Elliot B
EB
Bodofsky
Cooper Medical School of Rowan University, United States.
Stephen J
SJ
Cohen
Cooper Medical School of Rowan University, United States.
Rohini J
RJ
Kumar
Cooper Medical School of Rowan University, United States.
Adam
A
Schindelheim
Cooper Medical School of Rowan University, United States.
John
J
Gaughan
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002349:Carpal Tunnel Syndrome / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000503:physiopathology; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology; D009431:Neural Conduction; D011930:Reaction Time; D011984:Sensory Receptor Cells / Q000502:physiology*; D014459:Ulnar Nerve / Q000503:physiopathology
Neurophysiology; Sensory nerve conduction; Statistical model