We investigated many electrode, and electrode-gel combinations to use on the peripheral recording sites. Stimulation intensities should be sufficient to evoke maximal depolarization of the evaluated nerve. Inadequate stimulation intensities may elicit submaximal depolarization, thus invalidating the criteria for amplitude in differential diagnosis. We have divided the technique into two protocols. It involves stimulating the median, ulnar, and superficial sensory radial nerves just proximal to the wrist and the C6 and C7 dermatomes distal to the wr ist at sites on the first and third digits.
Sources do vary slightly with respect to innervation, and anatomical variances do exist.
A common reference on the forehead, kno wn as Fz', is chosen for each of the recording electrodes. A grounding electrode is placed between the stimulation and recording sites over the muscle bellies of the finger flexors on the forearm. It involves stimulating the posterior tibial and common peroneal nerves, which are the primary divisions of the lumbosacral plexus forming the sciatic nerve. The saphenous, superficial peroneal, and sural ner ves were then chosen for the primary component correlating with a particular lumbosacral nerve root, L4, L5 and S1 respectively. Recording electrodes are placed over the L1 and C2 spinous processes and over the corresponding area of the sensory cortex receiving afferent signals from the lower extremities.