Measurement of motor root conduction time at the early stage of Guillain–Barre syndrome

Abstract

As they are mainly performed at distal nerve parts, routine electrophysiological examinations can fail to detect the abnormalities at the early stage of Guillain-Barre syndrome (GBS) because of predominant involvement of proximal nerve segments. Measurements focused on proximal conduction can provide additional findings. We investigated the diagnostic significance of motor root conduction time (MRCT) at the early stage of GBS. Study was performed in 30 healthy volunteers and within the first week of 12 patients with GBS. MRCT was calculated as the latency differences between motor nerve conduction time (MNCT) obtained by cervical magnetic stimulation and total peripheral motor conduction time obtained by electrical stimulation of ulnar nerve. Also MNCT/MRCT ratio was calculated in each subject. There were statistically significant differences between groups for MRCT (P < 0.0001) and MNCT/MRCT ratio (P < 0.0001). Although the F-wave latency at ulnar nerve was abnormal only in 33%, MRCT was significantly prolonged in 83% of patients. In three patients, prolongation of MRCT was the only abnormality at the first electrodiagnostic examination. Motor root conduction time as a non-invasive method can provide additional and confirmative information at the early stage of GBS in which routine nerve conduction studies may fail to detect the focal demyelination.