Trigeminal somatosensory evoked responses in patients with facial anaesthesia dolorosa.

The TSER of six patients with facial anaesthesia dolorosa showed shorter latencies and higher amplitudes of the late waves, which are believed to represent the processing of somatosensory input in the higher subcortical and cortical centres. Shorter latencies and higher amplitudes may reflect abnormal facilitation or decreased inhibition by these centres. The TSER also supplied an objective means of pain measurement, as the stimulating impulse at the affected side had to be reduced from 20 mA (the usual intensity used in patients without evoking pain or an unpleasant sensation) down to 9-12 mA, to avoid unbearable pain.