ELECTRIC VERSUS MAGNETIC TRANSCRANIAL STIMULATION OF THE TRIGEMINAL SYSTEM IN HEALTHY-SUBJECTS - CLINICAL-APPLICATIONS IN GNATHOLOGY

This investigation is focused on the analysis of the masseter response s evoked by means of magnetic and electric stimulation of the cortex a nd root of the trigeminal system of 20 healthy subjects. Moreover, in order to determine jaw elevation in centric occlusion, the analysis al so focused on the motor response of the trigeminal bilateral roots evo ked simultaneously using two stimulators. The masseter responses show a high level of symmetry in both latency and amplitude. The difference between the hinge axis in natural centric occlusion (CO) and in centr ic relation (CR) as determined by electric and magnetic transcranial s timulation is lesser than 2.5 mm. This is due to two main factors: (i) the response is evoked from the trigeminal motor neural pool involvin g masticatory muscles and hence simulating natural 'muscular coactivat ion' (ii) there is no manual manipulation to guide the jaw into the ce ntric relation (CR). This method could be of some help for diagnosis i n patients suffering from TMJ dysfunction who have lost stereognostic control over the jaw and display obvious signs of deviation during clo sure of the mandible.