Background
and Objectives: The proximal and distal nerve segments are preferentially involved in acquireddemyelinating polyneuropathies (ADP). This study was undertaken in order to assess the usefulness of motor evokedpotential (MEP) and somatosensory evoked potential (SSEP) in the detection of the proximal nerve lesion in ADP.Methods: MEP, SSEP and conventional NCS were performed in 6 consecutive patients with ADP (3 AIDP, 3 CIDP).MEP was recorded from abductor pollicis brevis and abductor hallucis using magnetic stimulation of the cortex and thecervical/lumbar spinal roots. SSEP were elicited by stimulating the median and posterior tibial nerves. Latency fromcortex and cervical/lumbar roots, central motor conduction time (CMCT), EN1-CN2 interpeak latency were measuredfor comparison.Results: MEP was recorded in 24 limbs (12 upper and 12 lower limbs) and SSEP in 24 limbs (12 median nerve, 12posterior tibial nerve). F-wave latency was prolonged in 25 motor nerves (25/34, 73.5%). Prolonged CML and PMLwere found in 41.7% (10/24) and 45.8% (11/24), respectively. Interside difference (ISD) of CMCT was abnormallyincreased in the upper extremity, 66.7% (4/6 pairs) in case of CML-PML. EN1-CN2 interpeak latency was abnormallyprolonged in one median nerve (1/10) and LN1-P1 interpeak latency was normal in all posterior tibial nerves.Conclusions: MEP and SSEP may provide useful information for the proximal nerve and root lesion in ADP. MEPand SSEP is supplemental examination as well as complementary to conventional NCS.
