Three-dimensional curves: main parameters of brainstem auditory-evoked responses in the normal subject.

Brainstem evoked potentials (BER) have been studied in three dimensions (3D). It was necessary to record simultaneously three orthogonal derivations in the three spatial axes. The 3D curves obtained were formed by successive uncompletely locked loops which correspond with the first five waves of BER. Planar segment could be identified in the 3D curves; planes were defined by geometrical parameters, following standard analytic geometry. The 3D curves appeared to be symmetrical after right and left stimulation, and were almost completely flattened around the anteroposterior axis after binaural stimulation. This flattening was not observed in the case of multiple sclerosis.