Comparison of magnetic coil stimulation and needle electrical stimulation in the diagnosis of lumbosacral radiculopathy

Abstract

Electrical stimulation (ES) of lumbosacral nerve roots using a needle electrode inserted to the laminar level at the midline of Th12-L1 or L1-2 intervertebral interspace, was compared with magnetic stimulation using a 9-cm diameter coil (MCS) at the L3-4 or L4-5 spine levels, Compound muscle action potentials (CMAP) were superficially recorded from homologous muscles in both sides in 15 normal control subjects and in 20 patients with lumbosacral radiculopathy. Soleus muscles were used for S1, tibialis anterior (TA) for L5, and rectus femoris (RF) muscles for L4 roots. According to the clinical or radiological diagnosis (CAT, MRI and/or myelography) conventional needle EMG was capable to localise the root lesion in 16 of 20 patients (80%) and ES localised the root involvement in 18 of 20 patients (90%); the diagnostic value of MCS was lower, about 65% (13 of 20 patients). Although ES is uncomfortable and invasive, it is superior to needle EMG in localising unilateral or multiple lumbosacral root involvement. At present, MCS is not suitable for the diagnosis of lumbar radiculopathy.