FOCAL PARESTHESIAS WITH CERVICAL MAGNETIC STIMULATION

Subjects undergoing cervical magnetic stimulation with an appropriate coil report focal hand paresthesias in a dermatomal distribution, but the physiologic accuracy of such subjective experiences has been uncer tain. In six subjects, we used a butterfly-shaped magnetic coil to sti mulate positions on the back of the neck at l-cm intervals, constant o utput, and random order, while the subject-estimated location and inte nsity of paresthesias and sensory nerve action potentials (SNAPs) were recorded from the thumb or index finger. Three subjects each also had recording of finger accelerometry or compound motor action potentials (CMAPs) in the hand and forearm. We found a consistent correlation be tween subjective paresthesias and SNAPs but an appropriate anatomic di vergence between paresthesias and accelerometry or CMAPs. Focal parest hesias from cervical magnetic stimulation are reliable and anatomicall y accurate, strengthening the hypothesis that other magnetic sensory p henomena are valid as well.