Facilitation of motor evoked potentials: Timing of jendrassik maneuver effects

Abstract

Remote voluntary contraction, such as the classical Jendrassik maneuver (JM), is a procedure routinely used to increase the amplitude of tendon reflexes in the lower limb. In 8 healthy subjects we studied the effects of JM on the motor evoked potentials (MEP) recorded from tibialis anterior muscle, produced by transcranial magnetic stimulation (stimulus output of 5-10% over motor threshold). In this study, JM consisted here of a bilateral violent handgrip, preceding magnetic stimulation from 100 to 50 ms (steps of 100 ms). Compared to the control test, latencies remained unchanged. MEP amplitudes were greatly enhanced with a JM test interval from 200 to 400 ms (170% of control amplitude at 300 ms). We also studied 6 patients with severe alterations of MEPs from tibialis anterior muscle. In each case, JM preceding magnetic stimulation (stimulus output 100%) from 300 ms induced reappearance of response or marked enhancement of amplitude, allowing calculation of central conduction time. Such a technique, which is easy to perform, may be useful in clinical practice to calculate central motor conduction time, where it would otherwise be difficult or impossible.

Invariable H-reflex and sustained facilitation of stretch reflex with heightened sympathetic outflow

“…In contrast, the response in H-reflex to mental arithmetic and remote contraction is inconsistent (Bussel et al, 1978;Gregory et al, 2001;Rossi-Durand, 2002;Zehr and Stein, 1999). Sensitization of the muscle spindle (Burg et al, 1974;Ribot-Ciscar et al, 2000;Rossi-Durand, 2002) and presynaptic disinhibition (Delwaide and Toulouse, 1980;Péréon et al, 1995;Zehr and Stein, 1999) are proposed to be involved in the modulations of stretch and H-reflexes during these tasks.…”

“…The data were normalized to the mean value during the control period.tic disinhibition with the contraction of remote muscle(Gregory et al, 2001;Hultborn et al, 1987). Other groups observed presynaptic disinhibition(Delwaide and Toulouse, 1980;Péréon et al, 1995;Zehr and Stein, 1999), but it was only transient with the maximal…”

Remote facilitation of supraspinal motor excitability depends on the level of effort

“…Recently, MEPs in the upper and lower limb muscles following TMS were demonstrated to be facilitated during intense contraction of the remote muscle (Kawakita et al. , 1991; Péréon et al. , 1995; Muellbacher et al.…”

Residual descending motor pathways influence spasticity after spinal cord injury

“…23 Evidence showed that a Jendrassik maneuver also increases MEP size in lower limb muscles. 24,25 Therefore, during stimulation of participants with motor complete SCI, to ensure maximum drive to spinal motoneurons, individuals were also asked at times to perform a Jendrassik maneuver, where they needed to clench their teeth and flex their fingers or arms bilaterally, into a hooklike form, with rest periods as needed. TMS stimuli were delivered at 4 second intervals (0.25Hz) at an intensity of 100% of the maximum stimulator output in SCI (single and paired pulse) and control (single pulse) subjects.…”