Abstract

We elicited H-reflexes by magnetic and electrical stimulation of several different nerves in 10 healthy subjects and two patients with S-1 radiculopathy. The posterior tibial nerve at the popliteal fossa and the femoral nerve at the inguinal ligament were tested with both electrical and magnetic stimulation; the proximal sciatic nerve was tested only with magnetic stimulation. Muscle activity was recorded from the soleus muscle for posterior tibial and sciatic nerve stimulation and from the vastus medialis muscle for femoral nerve stimulation. No significant difference was found between the latency of H-reflexes evoked by magnetic or electrical stimulation. With magnetic stimulation, the mean (+/- SD) Ia sensory fiber conduction velocity in the proximal segment of the sciatic nerve was 72.4 +/- 3.3 m/s, while the motor nerve fiber conduction velocity in the same portion of the nerve was significantly slower, at 60.6 +/- 2.0 m/s. In two patients with unilateral S-1 radiculopathy, the latency of the H-reflex from the soleus muscle to both magnetic and electrical stimulation of the posterior tibial nerve was absent or prolonged on the affected side. Magnetic stimulation can be used to study the H-reflex and Ia fiber conduction velocity and is particularly advantageous when testing deeply located nerve trunks.

Highlights

  • We elicited H-reflexes by magnetic and electrical stimulation of several different nerves in 10 healthy subjects and two pa· tients with S-1 radiculopathy

  • Muscle activity was recorded from the soleus muscle for posterior tibial and sciatic nerve stimulation and from the vastus medlalis muscle for femoral nervestimulation

  • A comparison ofsoleus muscle H-reflexes with the use of magnetic coils 9 and 5 cm in diameter was performed in six subjects

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Summary

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Yu Zhu, MD; Arnold Starr, MD; Su Hwan Su, MD; K. Nerve at the popliteal fossa and the femoral nerve at the Inguinal ligament were tested with both electrical and magnetic stimulation; the proximal sciatic nerve was tested only with magnetic stimulation. In two patients with unilateral S-1 radiculopathy, the latency of the H·refle.x from the soleus mu scle to both magnetic and electrical stimulation of the posterior tibia! Magnetic stimulation can be used to study the H-reflex and la fiber conduction velocity and is advantageous when testing deeply located nerve trunks. H offrnann' originally described the electrically induced monosynaptic reflex CH-reflex) occurring in calf muscles ofhumans on stimulation ofthe posterior tibial nerve at the popliteal fossa. Reprint requests to the Department of Neurology, University of California, Irvine, Irvine, CA 92il[7] (Dr Zhu).

SUBJECTS AND METHODS
Magnetics Stimulation
Direction of Current Flow in the Coil
Posterior Tibial
Difference Between Two
Magnetic Stlmulatlon of Sacral Nerve Roots
Findings
In Healthy Subfects
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