Paroxysmal itching in multiple sclerosis during treatment with external magnetic fields.

Paroxysmal attacks of itching constitute a rare sensory symptom of multiple sclerosis (MS). It is generally thought that paroxysmal itching, a form of subthreshold pain sensation, is caused by transversely spreading ephaptic activation (i.e., activation via an artificial synapse) of axons within a partially demyelinated lesion in fiber tracts in the CNS, most commonly in the spinal cord. In MS, attacks of paroxysmal itching have been reported to occur either as the initial symptom of the disease or at the onset of an acute relapse. I present two female MS patients aged 36 and 40 years in whom paroxysmal itching was a prominent sensory symptom which occurred at the onset of treatment with external picoTesla range magnetic fields (MF) and coincident with the process of neurologic recovery. This report suggests that picoTesla range MF may cause activation of neuronal transmission along partially demyelinated axons of pain conduction in the spinal cord. The occurrence of rapid neurologic recovery with initiation of treatment with MF supports the notion that impaired synaptic conductivity rather than demyelination underlies some of the neurologic deficits of MS.