H-reflex and M-wave responses after voluntary and electrically evoked muscle cramping

PURPOSE

Despite the widespread occurrence of muscle cramps, their underlying neurophysiological mechanisms remain unknown. To better understand the etiology of muscle cramps, this study investigated acute effects of muscle cramping induced by maximal voluntary isometric contractions (MVIC) and neuromuscular electrical stimulation (NMES) on the amplitude of Hoffmann reflexes (H-reflex) and compound muscle action potentials (M-wave).

METHODS

Healthy men (n = 14) and women (n = 3) participated in two identical sessions separated by 7 days. Calf muscle cramping was induced by performing MVIC of the plantar flexors in a prone position followed by 2.5-s NMES over the plantar flexors with increasing frequency and intensity. H-reflexes and M-waves evoked by tibial nerve stimulation in gastrocnemius medialis (GM) and soleus were recorded at baseline, and after MVIC-induced cramps and the NMES protocol.

RESULTS

Six participants cramped after MVIC, and H-reflex amplitude decreased in GM and soleus in Session 1 (- 33 ± 32%, - 34 ± 33%, p = 0.031) with a similar trend in Session 2 (5 cramped, p = 0.063), whereas the maximum M-wave was unchanged. After NMES, 11 (Session 1) and 9 (Session 2) participants cramped. H-reflex and M-wave recruitment curves shifted to the left in both sessions and muscles after NMES independent of cramping (p ≤ 0.001).

CONCLUSION

Changes in H-reflexes after a muscle cramp induced by MVIC and NMES were inconsistent. While MVIC-induced muscle cramps reduced H-reflex amplitude, muscle stretch to end cramping was a potential contributing factor. By contrast, NMES may potentiate H-reflexes and obscure cramp-related changes. Thus, the challenge for future studies is to separate the neural consequences of cramping from methodology-based effects.

Neuromuscular Electrical Stimulation Reduces Leg Cramps in Patients With Lumbar Degenerative Disorders: A Randomized Placebo-Controlled Trial

Objectives

Lumbar spinal stenosis (LSS) and lumbar disc herniation (LDH) are often accompanied by frequently occurring leg cramps severely affecting patients' life and sleep quality. Recent evidence suggests that neuromuscular electric stimulation (NMES) of cramp‐prone muscles may prevent cramps in lumbar disorders.

Materials and Methods

Thirty‐two men and women (63 ± 9 years) with LSS and/or LDH suffering from cramps were randomly allocated to four different groups. Unilateral stimulation of the gastrocnemius was applied twice a week over four weeks (3 × 6 × 5 sec stimulation trains at 30 Hz above the individual cramp threshold frequency [CTF]). Three groups received either 85%, 55%, or 25% of their maximum tolerated stimulation intensity, whereas one group only received pseudo‐stimulation.

Results

The number of reported leg cramps decreased in the 25% (25 ± 14 to 7 ± 4; p = 0.002), 55% (24 ± 10 to 10 ± 11; p = 0.014) and 85%NMES (23 ± 17 to 1 ± 1; p < 0.001) group, whereas it remained unchanged after pseudo‐stimulation (20 ± 32 to 19 ± 33; p > 0.999). In the 25% and 85%NMES group, this improvement was accompanied by an increased CTF (p < 0.001).

Conclusion

Regularly applied NMES of the calf muscles reduces leg cramps in patients with LSS/LDH even at low stimulation intensity.

Evaluation of foot position and orientation as manipulated variables to control external knee adduction moments in leg extension training

BACKGROUND AND OBJECTIVE

Effective leg extension training at a leg press requires high forces, which need to be controlled to avoid training-induced damage. In order to avoid high external knee adduction moments, which are one reason for unphysiological loadings on knee joint structures, both training movements and the whole reaction force vector need to be observed. In this study, the applicability of lateral and medial changes in foot orientation and position as possible manipulated variables to control external knee adduction moments is investigated. As secondary parameters both the medio-lateral position of the center of pressure and the frontal-plane orientation of the reaction force vector are analyzed.

METHODS

Knee adduction moments are estimated using a dynamic model of the musculoskeletal system together with the measured reaction force vector and the motion of the subject by solving the inverse kinematic and dynamic problem. Six different foot conditions with varying positions and orientations of the foot in a static leg press are evaluated and compared to a neutral foot position.

RESULTS

Both lateral and medial wedges under the foot and medial and lateral shifts of the foot can influence external knee adduction moments in the presented study with six healthy subjects. Different effects are observed with the varying conditions: the pose of the leg is changed and the direction and center of pressure of the reaction force vector is influenced. Each effect results in a different direction or center of pressure of the reaction force vector.

CONCLUSIONS

The results allow the conclusion that foot position and orientation can be used as manipulated variables in a control loop to actively control knee adduction moments in leg extension training.

Effects of Neuromuscular Electrical Stimulation on the Frequency of Skeletal Muscle Cramps: A Prospective Controlled Clinical Trial

OBJECTIVES

We investigated if neuromuscular electrical stimulation (NMES) of calf muscles prevents spontaneous calf cramps.

MATERIALS AND METHODS

In 19 individuals affected by more than or equal to one calf cramp per week the gastrocnemius of the predominantly affected leg was stimulated twice a week (intervention leg, IL) over six weeks (3 × 6 stimulation trains at 30 Hz above the individual cramp threshold frequency). The other leg served as control (CL). The participants were advised to record all spontaneous muscle cramps from two weeks before the intervention until two weeks after the last NMES session.

RESULTS

The number of spontaneous calf cramps in the two weeks after the intervention was 78% lower (2.1 ± 6.8 cramps) in the stimulated (p < 0.001) and 63% lower (2.0 ± 6.9 cramps) in the unstimulated calves (p < 0.001), when compared to the two weeks prior to the intervention (IL: 9.6 ± 12.4 cramps; CL: 5.5 ± 12.7 cramps). Only in the IL, this improvement was accompanied by an increase in the cramp threshold frequency from 15.5 ± 8.5 Hz before the NMES intervention to 21.7 ± 12.4 Hz after the intervention. The severity of the remaining calf cramps tended to be lower in both legs after the intervention.

CONCLUSIONS

The applied stimulation protocol seems to provide an effective prevention strategy in individuals affected by regular calf cramps.

[Sarcoma of the pulmonary artery--pre- and postoperative radiologic findings in initial tumor manifestation and recurrence]

PURPOSE

Primary pulmonary artery sarcomas are very rare tumors. Their diagnosis is difficult due to their unspecific symptoms. Still, an early preoperative diagnosis is the only possibility for a potential therapy.

PATIENTS AND METHODS

4 pre- and 5 postoperative CT- and three pre- and one postoperative MRT-examination(s) have been evaluated with respect to surgical and histological findings.

RESULTS

The presence of a convex intraluminal bulging mass spreading mostly from the pulmonary trunc continuously into the peripheral pulmonary artery branches the filling and dilatation of the vessels, the tumor's inhomogeneity indicating hemorrhages and necrosis and the appearance of intrapulmonary nodules are found in both CT and MRI. Recurrent pulmonary artery sarcoma features an extravascular growth and is similar to lung cancer affecting the vessels. It shows contrast enhancement both in CT and MRI while the primary tumor shows a distinct contrast enhancement only of Gadopentetate dimeglumine but none or little enhancement in CT.

CONCLUSION

The criteria presented in knowledge of CT and MRI serve to increase the probability for a correct preoperative diagnosis and thus allow adequate surgical planning.

[Intracerebral hemorrhage after systemic thrombolysis in patients with occlusion of the central retinal artery. Report of 2 cases]

Pharmacological thrombolysis is a valuable therapeutic modality for embolic arterial occlusion. Nevertheless, thorough evaluation of the indications is imperative to avoid serious complications. The most frequent complication is hemorrhage. Of these, the intracerebral hemorrhages are rare, but when they do occur they are an immediate threat to life they are accompanied by very severe complications, and they have an extremely poor prognosis. Within 58 months 361 patients were treated at our neurosurgical clinic with intracerebral hematomas. In 22 patients (6.1%) the hematoma developed as a complication of systemic thrombolysis. Two of these patients had been treated for occlusion of the central retinal artery. One patient died: the other survived but was severely disabled. The latter patient experienced no benefit from the thrombolysis as for as the underlying ophthalmologic disease was concerned. These worrying examples stress the necessity for careful evaluation of risk factors and the natural history of the underlying disease for which systemic thrombolysis is indicated. Local selective (or superselective) thrombolysis is preferable to the systemic procedure, provided that the indications are equally strictly observed and are less likely to lead to severe complications.