Weak electromagnetic fields increase the amplitude of the pattern reversal VEP response in patients with multiple sclerosis.

Visual evoked potential (VEP) studies are widely used for the diagnosis of multiple sclerosis (MS) and are also useful in monitoring the effects of various therapeutic modalities in the disease. Brief, extracerebral applications of picotesla (pT) range flux intensity electromagnetic fields (EMFs) of low frequency have been shown efficacious in the treatment of motor and cognitive symptoms in MS implying that this treatment modality improves action potential transmission in demyelinating pathways. This report documents three MS patients with a remitting-progressive course in whom two successive brief extracerebral applications of pT range EMFs caused an immediate increase (and normalization) of the amplitudes of the visual evoked response in the eye previously affected by optic neuritis. However, the pretreatment prolonged latencies of the evoked responses remained essentially unchanged after the administration of EMFs. Since the latency of the VEP reflects the degree of conduction velocity and the amplitude the degree of conduction block in demyelinating optic pathways, the report demonstrates that extracerebral applications of these EMFs may rapidly reverse conduction block in demyelinating fibers. Reversal of the conduction block, which is though to be related to changes in axonal Na+ and K+ channels and synaptic neurotransmitter release, accounts for the immediate improvement of vision and other neurological deficits observed in MS patients following exposure to these EMFs.