Intravenous lidocaine and magnesium on responses of A-δ and A-β nerve fibers at non-affected and affected areas in three cases of neuralgias

Intravenous magnesium and lidocaine have been used for the management of intractable pain individually or in combination. A study reported on the positive effects when used in combination on neuralgia when antiepileptic drugs failed, but nobody has clarified how the combination works. The aim of the present case report is to see how a combination of intravenous magnesium and lidocaine influenced electrically-evoked responses of peripheral A-δ and A-β nerve fibers at non-affected and affected areas in three patients with neuralgia. For nociceptive stimulation, a method of intraepidermal electrical stimulation (IES) was used for the selective activation of cutaneous A-δ fibers, using a stainless steel concentric bipolar needle electrode. For tactile stimulation, similar cutaneous sites were stimulated for cutaneous A-β fibers using the same electrode. Three patients with intractable trigeminal neuralgia or intercostal neuralgia were treated using an intravenous infusion of a combination of 1.2g of magnesium and 100mg of lidocaine for one hour. Although all patients experienced sound pain relief after the combined intravenous infusion therapy, the combination had a different effect on electrically-evoked responses of peripheral A-δ and A-β nerve fibers at non-affected and affected areas in each patient.