Noncortical Origins of the Spinal Motor Evoked Potential in Rats

Abstract

Two hundred seventy consecutive patients operated upon by standard discectomy were compared to 270 patients treated with microlumbar discectomy. All patients had back and leg pain, as well as positive clinical findings and positive myelograms suggestive of disc herniation. The results demonstrated a 98% success rate in the microsurgical group as compared to a 95% success rate in the standard laminectomy group. Of microdiscectomy patients, 95% had an excellent result, as compared to 89% of the standard laminectomy group. Patients with pending compensation cases did only slightly poorer than those with no secondary gain regardless of what procedure was used. The postoperative hospital stay of the microsurgical patients averaged 3.7 days as compared to 7.1 for the standard technique. The time before return to work was significantly shorter in patients undergoing microdiscectomy. Microdiscectomy proved to be superior in both clinical results and cost effectiveness.

Conduction pathways of motor evoked potentials following transcranial magnetic stimulation: A rodent study using a ?Figure-8? coil

“…7,14 Because the origins and conduction pathways of magnetic MEPs in the rat may differ from those in other animals, in the rat we further compared magnetic MEPs with MEPs obtained following monopolar or bipolar electric stimulation in the same way as in previous studies. 9,22,25,29 According to Zappulla et al 1,29 and Fujiki et al, 9 monopolar electric MEPs in rats originate from the subcortical and brain stem structures and conduct activity from the ventral and lateral funiculi in the spinal cord, reflecting extrapyramidal system function. Their technique of putting the cathode in the submucosa of the hard palate may make it easy to obtain extrapyramidal excitation.…”

“…4,9,13,22,29 If approached dorsally, however, it is easy to cut the dorsal funiculus, but very difficult solely to ablate the ventral funiculus without compromising the dorsal and lateral funiculi. Therefore, we selectively dissected the ventral funiculus by an anterior approach through the disk space, as verified histologically (Fig.…”

“…1,9,22,25,29 For monopolar electric stimulation, a 0.8-mm silver ball electrode (Unique Medical, Kyushu, Japan) was set on the pial surface as the anode, and a needle electrode was inserted into the submucosa of the hard palate as the cathode. Bipolar electric stimulation was delivered between 2 stainless steel electrodes (Unique Medical), 0.25 mm in diameter and 1 mm apart, being the anode set laterally.…”

Olfactory ensheathing cells transplanted in lesioned spinal cord prevent loss of spinal cord parenchyma and promote functional recovery

“…Motor-evoked potentials (MEPs) were recorded using monopolar needle electrodes placed at the tibialis anterior muscle, while the contralateral sensorimotor cortex was stimulated by single rectangular pulses of 0.1-ms duration, delivered through needle electrodes inserted subcutaneously, the cathode over the skull overlying the sensorimotor cortex and the anode at the nose. This configuration produces transcranial stimulation that activates subcortical efferent pathways (Zappulla et al 1988;Adamson et al 1989). For somatosensory-evoked potentials (SSEPs), electrical stimuli 0.1 ms in duration and 4 mA in intensity were applied at 5 Hz to the tibial nerve by means of two needle electrodes inserted at the ankle.…”

Morphological and electrophysiological evidence for regeneration of transected spinal cord fibers and restoration of motor functions in adult rats

“…The studies on selective spinal cord injuries demonstrated that short-latency MEPs are conducted in the lateral and ventral funiculi ， while conduction of long-latency signals depends on the integrity of the dorsal funiculus [12,[14][15][16] . For a rat, the rubrospinal tract is located in the dorsolateral funiculus, with a mean conduction velocity (CV) of 74 m/s for directly activated rubrospinal axons; the raphespinal and the reticulospinal tract are located in the lateral and ventral funiculi [17,18] ; the CV for reticulospinal axons have been reported to range between 16-80 m/s [19] and 50-76 m/s [20] ; the corticalspinal tract is located at the base of the posterior columns of the cord [21] ; the tract is composed of a large number of unmyelinated and small diameter myelinated fibers, and the CV of this tract ranges from 5 to 19 m/s [22,23] . Short-latency muscle potentials (5-8 ms) are considered to originate in the brainstem, while those with latencies larger than 15 ms are believed to represent cortical MEPs [13,14,24] .…”