Correlation between F-waves of electromyography and spasm in patients with spinal injury

Yali LIU; Wei GAO; Chunjing YOU; Tiecheng GUO; Tao XU; Lan YU

ABSTRACT

BACKGROUND:

After the damage of central nervous system, F-waves of electromyography is the valuable way for detecting tendon reflex and muscular tension below injured segment. The increase of spasm, stiffness and muscular tension induced by upper motor neuron injury can revoke change of F-waves.However, change of F-waves after spinal injury, and relationship between Fwaves and spasm of lower limb after injury are still unclear at present.

OBJECTIVE:

To analyze the correlation of minimal latency, occurrence rate and every index of dispersion-time degree of F-waves with post-injured spinal cord spasm in patients with spinal injury.

DESIGN:

Case-control observation.

SETTING:

Department of Rehabilitative Medicine, Tongji Hospital Affiliated to Tongji Medical College, Huazhong University of Science and Technology.

PARTICIPANTS:

Totally 29 patients with traumatic spinal cord injury,who were hospitalized at Department of Rehabilitative Medicine, Tongji Hospital Affiliated to Tongji Medical College, Huazhong University of Science and Technology between June 2002 and March 2004, were selected as spinal injury group. Another 29 normal healthy volunteers were enrolled as normal control group in the same period.

METHODS:

Spasm level of both lower extremities in patients with spinal injury was graded with Ashworth scale to assess flexion of both coax, flexion of knee joint and Ashworth grade of dorsiflexion of ankle. F-waves was detected with Kepoint1.5 type EMG instrument produced by Denmark.Minimal latency, maximal latency and occurrence rate of F-waves of tibial nerve of both lower extremities were recorded. The discrete-time degree (difference value of maximal latency of F-waves and minimal latency of Fwaves) and mean occurrence rate of F-waves were calculated.MAIN OUTCOME

MEASURES:

The difference of each index between patients with spinal injury and normal persons was compared and the correlation of spasm with discrete-time degree, occurrence rate and minimal latency of F-waves in patients with spinal injury was analyzed.

RESULTS:

A total of 29 patients and 29 normal persons were involved in the result analysis. ①The discrete-time degree of F-waves in patients with spinal injury was higher than that in the normal persons, which had significant difference [(9.2±1.9), (6.7±1.0) ms, P ＜ 0.000 1]. ②The occurrence rate of F-waves in patients with spinal injury was lower than that in normal persons, which had significant difference [(84.5±6.2)%, (89.5 ±5.7)%, P ＜ 0.05]. ③The minimal latency of F-waves in patients with spinal injury was higher than that in normal persons, which had insignificant difference ( P ＞ 0.05). ④The discrete-time degree of F-waves in patients with spinal injury had positive correlation linearly with score of spasm Ashworth (r=0.790 31, P＜ 0.000 1). The occurrence rate of Fwaves in patients with spinal injury had positive correlation linearly with score of spasm Ashworth (r=0.742 03, P ＜ 0.000 1 ). The minimal latency of F-waves in patients with spinal injury had insignificant correlation with score of spasm Ashworth (r=0.081 68, P ＞ 0.05).

CONCLUSION:

The discrete-time degree and occurrence rate of F-waves can be used as sensitive index to evaluate electrophysiology in patients with spinal injury so as to assess the level of spasm in patients with spinal injury.