Changes in the Motor and Sensory Latencies of Median Nerve According to Age

Even though there is a high prevalence of carpal tunnel syndrome patients, there are very few reliable papers on the study of normal values and changes in sensory and motor latency parameters of the median nerve in the wrist region on the basis of age of patients .This retrospective study was on the basis of 5 years data (1998 -2003) from the electro diagnostic department of Sh. Sadoughi teaching hospital of Yazd.

In this analytic and observational study, subjects included 1200 patients referring to the electrodiagnostic clinic and also randomly selected healthy patients. Exclusion criteria included systemic diseases such as diabetes, radiculopathy of cervical spine , peripheral neuropathy , positive Phallen test or Tinel sign and atrophy in the thenar region of the hand. Subjects were divided to ten groups on the basis of age. ( 10-80 years ) Sensory and motor latency parameters of median nerve were studied in each age group. All data was evaluated using SPSS statistical software and ANOVA , LSDREST curve regression tests were used for analysis. All values less than 0.05 were considered significant.

In this study, normal values for distal motor latency of median nerve were between 2.5-4.2ms with a ±2SD and mean value of 3.3ms. Increment in this value was mild (0.1ms per decade) after 5th decade of life. This value was calculated using the formula: Distal motor latency: Normal value for distal sensory latency of median nerve was 2.7-3.7ms with a ±2SD and mean value of 3.2ms. Increment in this value also was 0.1ms per decade after 5th decade of life. This value was calculated by the formula: Distal sensory latency:

It seems that age has a meaningful relationship with distal motor and sensory latencies in the wrist region and therefore in the future, electro diagnostic evaluation along with other increments in these parameters according to age should be considered when evaluating patients with carpal tunnel syndrome.