Magnetic stimulation of the brain. Comparison of circular coil v/s. double coil

Magnetic stimulation has introduced a new dimension in clinical neurology. The painless and non invasive cortical stimulation permits diagnosis of lesions in the central nervous system (CNS). It is well suited for deep peripheral nerves such as the lumbar and cervical roots. This method of stimulation is very safe as there is no direct contact between the patient and stimulating electrodes. When the coil is brought into proximity with the body a small current is induced in the tissue. If this current is of sufficient amplitude and duration, nerve and muscle-fibres are stimulated in the same way as with electrical stimulation. Comparisons of magnetic field and induced electric field for circular and double coil are discussed. The comparison study shows that the double coil is more localized than the circular coil.