being transmitted along the median nerve to the recording electrode 26 the amplitude of the stimulus pulses is set by means of amplitude control 38 which is initially adjusted to a low amplitude or a known amplitude as set from a prior use a brief twitch of the muscles at the base of the thumb will occur as the motor nerves are activated the motor nerve twitching indicates that a proper contact path along the nerve has been established and that the stimulus voltage is sufficiently high since the threshold for activation of the sensory branch being evaluated is lower than the threshold for motor nerves users quickly adapt to the unusual sensation of the very brief shock pulses and the associated muscle twitch a series of latency measurements are then registered on the display 34 providing the user with diagnostic information about the sensory delay along the particular nerve being evaluated which in this case is the median nerve high latency periods exceeding approximately three milliseconds for the median nerve often are attributable to the compression of the median nerve by the carpal tunnel which is the condition commonly referred to as carpal tunnel syndrome a reading below three milliseconds covers at least 95 of normal asymptomatic subjects the higher reading is even more meaningful if the subject has been experiencing numbness or tingling in the hand or fingers in view of the simple self diagnostic procedure and the low cost for the apparatus itself periodic diagnostic evaluations can be warranted for individuals at risk of repetitive motion activities or for checking the positive effects of ergonomic interventions designed to mitigate repetitive motion effects response to simple treatments such as.