Study aim. - This prospective study aim to examine whether clinical findings and electrodiagnostic testing (EDX) in patients with lumbosacral monoradiculopathy due to herniated disc (HD) differ as a function of root involvement level (L5 vs. S1) and HD zone (paramedian vs. intraforaminal).Patients and methods. - All patients with L4, L5 or Si monoradiculopathy were prospectively enrolled at four electromyography (EMG) labs over a 2-year period. The diagnosis was based on a congruence between patient history and MRI evidence of HD. We compared the sensitivities of clinical findings and EDX with respect to both root involvement level and HD zone. Multivariate logistic regression was performed in order to verify the association between abnormal EMG, clinical, and neuroradiological findings.Results. - One hundred and eight patients (mean age 47.7 years, 55% men) were consecutively enrolled. Sensory loss in the painful dermatonne was the most frequent finding at physical examination (56% of cases). EMG was abnormal in at least one muscle supplied by femoral and sciatic nerves in 45 cases (42%). Inclusion of paraspinal muscles increased sensitivity to only 49% and that of proximal muscles was useless. Motor and sensory neurography was seldom abnormal. The most frequent motor neurographic abnormalities were a delay of F-wave minimum latency and decrease in the compound muscle action potential amplitude from extensor digitorum brevis and abductor hallucis in L5 and S1 radiculopathies, respectively. Sensory neurography was usually normal, the amplitude of sensory nerve action potential was seldom reduced when HD injured dorsal root ganglion or postganglionic root fibres. Multivariate logistic regression analysis showed that EMG abnormalities could be predicted by myotomal muscular weakness, abnormal deep reflexes, and paraesthesiae. The only clinical and electrophysiological differences with respect to root involvement level concerned deep reflexes and motor neurography of deep peroneal and tibial nerves.Conclusions. - Only some EDX parameters are helpful for the diagnosis of lumbosacral radiculopathy. EMG was abnormal in less than 50% of cases and its abnormalities could be predicted by some clinical findings. However, neurography is useful as a tool for differential diagnosis between radiculopathy and more diffuse disorders of the peripheral nervous system (polyneuropathy, plexopathy). (C) 2013 Elsevier Masson SAS. All rights reserved.

Objective: Normal sensory nerve action potential (SNAP) amplitude is a classical neurographic rule whether damage is located proximal to the dorsal root ganglion (DRG) as in radiculopathy. The study's aim is to check SNAP reduction in patients with lumbosacral radiculopathy due to herniated disc (HD).Methods: A total of 108 consecutive patients with lumbosacral monoradiculopathy were prospectively enrolled. The diagnosis was based on clinical findings and magnetic resonance imaging (MRI). Electromyography of muscles of L4-S1 myotomes, motor neurography of peroneal and tibial nerves and sensory neurography of saphenous, superficial peroneal and sural nerves were performed. Percentage decrease in SNAP amplitude of nerves between healthy and affected sides was calculated.Results: Significant SNAP amplitude asymmetry was observed in superficial peroneal nerve in seven patients with L5 (12.1%) and in sural nerve in one patient with S1 (2.4%) radiculopathies. All these patients had foraminal HD.Conclusions: SNAP amplitude reduction of sensory nerve originating from damaged root is present only in 7% of radiculopathies and is likely due to DRG compression when located proximal to the spinal foramen or within the intraspinal canal.Significance: Preservation of SNAP amplitude in radiculopathy remains an electrophysiological dogma with a little exception. If the reduction of SNAP amplitude affects other nerves, causes other than radiculopathy should be sought. (C) 2012 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.