Delayed habituation in Behcet's disease.

Background: The autonomic nervous system in Behcet's patients may be affected due to various reasons. This entity may be detected with the measurement of the electrodermal activities, heart rate variability and pupillometric methods. Habituation is one of the implicit forms of learning and memory and the loss of habituation can reveal pathological changes in the synaptic regions. Aim: To determine whether there is a functional decrease in the synaptic effectiveness (habituation) of the pathways to sympathetic neurons that had been repeatedly activated in Behcet's. Materials and Methods: Twelve patients with Behcet's disease and 12 healthy controls were included in the study. Sympathetic skin potential (SSP) records were taken at normal room temperature in a quiet place within a Faraday cage. Sixteen square wave single shock impulses (duration: 1200 ms, strength: 5 mA) were applied on each case. Results: After the 1 st stimulus, the SSP amplitudes were lower in the patients compared to the controls ( P < 0.001, t value = 7.69). There was no significant differences among the SSP amplitudes after the 13 th impulse in the patients ( P> 0.05). Whereas there was no significant differences among the SSP amplitudes after the 9 th impulse in the controls ( P> 0.05). The habituation rate of the SSP after consecutive impulses was slowest in the patients compared to controls ( P < 0.001, t value = 12.39). Conclusions: There is a delayed habituation in Behcet's disease and that may due to pathologic changes with vasculitis through their peripheral nerves.