Electromyography and clinical neurophysiology最新文献

Purpose: Hearing level in some children may be abnormal due to conductive or sensorineural causes. In Kuwait, the hearing screening test is not conducted for newborns at public hospitals. We evaluated the hearing level of 159 Kuwaiti school children (age 6-12 years) at the Audiology Clinic of Ahmadi hospital to determine the extent and causes of hearing loss in these children.

Methods: Each child was evaluated by otoscopic examination, tympanogram, acoustic reflex threshold (ART), audiogram, and distortion product oto-acoustic emission (DPOAE).

Results: 120 children were found to have normal ear conditions, while 39 children had abnormal results. The abnormalities were 21 children with ear wax, 16 children with secretory otitis media (SOM), and 2 children with sensorineural hearing loss (SNHL). In the children with ear wax, 3 had normal hearing level, while 18 had mild conductive hearing loss in the 250-500 Hz frequency range. In the children with SOM, 3 had normal hearing level, 9 had mild conductive hearing loss in the 250-500 Hz frequency range, while 4 had moderate conductive hearing loss in the 250-2000 Hz frequency range. The children with SNHL had moderate hearing loss in the 4000-8000 Hz frequency range.

Conclusion: Wax in the ear canal and SOM were the main factors associated with hearing loss in these Kuwaiti school children. It is necessary to establish a national program of school entry hearing screening in Kuwait.

Purpose: To evaluate the pattern of activation of the masticatory muscles in dysphonic women.

Methods: Seventeen women was divided into two groups: experimental group with 10 dysphonic women (33.6 +/- 8.0) and control group with 7 healthy women (25 +/- 5,19). The Electromyography exam of the left (LM) and right (RM) masseter muscles, anterior portion of the right (RT) and left (LT) temporal, and suprahyoid (SH) was performed by using electrodes of simple distinguishing surface.

Results: With the mandible postural position at rest, all the muscles presented increased electromyography activity compared to the control group (p < 0.05). As for the mandible elevator muscles, the RM experimental group presented significantly decreased electromyography activity (p < 0, 05) and the SH increased (p < 0.05) compared to the control group. For the rest of the muscles, there was no significantly difference between the groups. It was verified that the experimental group presented higher co-contraction of the mandible depressed muscles in relation to contraction of the RT LT, RM and LM, as compared to the control group (p < 0.05).

Conclusions: Dysphonic women present alteration of the activation patterns of the masticatory muscles.

It was analized the deltoid muscle anterior portion and the pectoralis major clavicular portion in 24 male volunteers using a two-channel electromyograph TECA TE 4, and Hewllet Packard surface electrodes, in 4 modalities of military press exercises with open grip. The results showed high inactivity for PMC in almost all the modalities while DA developed very high levels of action potentials in all the modalities assessed.

Objective: Mechanoreceptors from the foot sole likely contribute in the reflex regulations. Therefore, it was hypothesized that repetitive low threshold afferents stimulation would have an inhibitory effect on the soleus H-reflexes.

Methods: Sixteen normal subjects voluntarily, participated in the study and were randomly allocated. Subjects were remained in prone position. The Cutaneous Mechanical Pressure (CMP equal to 50% of leg and foot weight) was applied to the ipsilateral lateral and Medial plantar surface by a designed instrument through a square plate (30 x 30 mm). H reflex as an indicator for excitability of motoneurones was bilaterally elicited before and after the application of the CMP. The H-reflex parameters were estimated.

Results: Mechanical pressure significantly depressed soleus H-reflex excitability in ipsilateral and contralateral feet in all subjects.

Conclusion: The demonstration of a decrease in H-reflex excitability as a result of applied pressure to the foot sole suggests that the change in reflex excitability is the result of a common spinal mechanism. The results highlight the modulatory effects that natural stimulation of afferents can have on reflex excitability.

Significance: The placement of a small flat plate, in order to apply pressure to the plantar eminence, may be useful for modulation of muscle tone. In addition, these findings might be useful for reducing spasticity; because spasticity is at least partially caused by hyperexcitability of the motorneuron pool.

Standing and walking balance decreases in many kinds of neuromuscular, musculoskeletal and sensory disorders, and in elderly people because of age-related physiologic diminution. Recent studies have shown that contact cues from a cane or a fingertip provide information that leads to reduced postural sway in subjects. The first purpose of this study was to investigate the influence of light and forceful fingertip contacts with a wall on the postural sway while standing upright. The second purpose was to investigate the influence of fingertip contact on the EMG activity of the soleus muscle. Twelve healthy male volunteers (20.8 +/- 0.7 years old) participated in this study. Standing balance or postural sway was measured by sway of the center of pressure (COP) under three conditions: (1) standing without touching a wall, (2) standing with the right index fingertip lightly touching (< 1N) to a wall (3), and standing with the right index fingertip forcefully touching (5 approximately 10N) to a wall. Bipolar surface electrodes were placed over the right soleus muscle to measure EMG activity associated with anterior-posterior sway. More significant length, and rectangular and environmental areas of the COP were observed while standing without touching a wall than while standing while lightly or forcefully touching a wall, but there was no significant difference between the two touching conditions. No significant difference in the EMG activity of the soleus muscle was observed among the three conditions. The results of this study suggested that the fingertip touch contact with a wall decreased sway during static standing but did not influence the EMG activity of the soleus muscle.

Unlabelled: The electromyographic (EMG) mean power frequency (MPF) and amplitude versus time relationships are commonly used to characterize localized muscle fatigue.

Purpose: The purpose of this study was to compare the effect of epoch length on the individual and mean slope coefficients and y-intercepts resulting from the EMG MPF and amplitude versus time relationships of the vastus medialis (VM) muscle during fatiguing isometric muscle actions at 30 and 75% of maximum voluntary isometric contraction (MVC).

Methods: Eight adults performed two continuous, isometric muscle actions of the leg extensors at 30 and 75% MVC to exhaustion. Six, 5.0 s epochs of the surface EMG signals were recorded from the VM during each minute. Epoch lengths of 0.5, 1.0, and 2.0 s were selected from the middle of each 5.0 s epoch. Linear regression was used to estimate the slope coefficient and y-intercept values for the EMG MPF and amplitude versus time relationships for each epoch length (0.5, 1.0, 2.0, and 5.0 s) and subject.

Results: There were no significant differences between epoch lengths for the individual or mean slope coefficients or y-intercepts (EMG MPF and amplitude versus time relationships).

Conclusion: This study indicated that epochs of 0.5 - 5.0 s resulted in the same characterization of EMG (MPF and amplitude) versus time relationships during isometric muscle actions.

Temperature affects distal sensory & motor latencies & nerve conduction velocity but not necessarily at the same degree. Purpose of this study is to see which one is affected less and thus could be more reliable in cold conditions. A total of 32 healthy individuals with age range of 18-28 years (mean 22.25 +/- 2.2) participated in this study. Skin Temperature was recorded at wrist. Distal median motor & sensory latencies and transcarpal median NCV were recorded before and after immersion in cold water. Statistical analysis was performed using paired t-test with SPSS. All parameters were affected by cold but the effect was less dramatic in transcarpal NCV. Transcarpal median NCV is least affected parameter by cold, so it may be more reliable than sensory & motor latencies at wrist.

Objective: To investigate clinical features of postural instability and the relationship between severity of instability and falls during daily living in patients with Parkinson's disease (PD).

Methods and subjects: We recorded trunk movements of subjects maintaining a seated position for 2 minutes using both a force plate and a position sensor system. We compared 13 patients with falls (fallers), 7 without falls (non-fallers), and 8 age-matched normal controls.

Results: The tendency for the values of both lateral COP displacement and trunk displacement was to increase in 1) patients compared with controls, and 2) fallers compared to non-fallers. Among patients who showed a large value of lateral COP displacement, greater than the value of the mean plus one standard deviation of controls, 90% had lumbar scoliosis and 60% of these patients fell down more than 5 times during the one-year follow-up period.

Conclusion: We demonstrated that PD patients who had fallen frequently tended to have a 1) lumbar scoliosis, and 2) large value of lateral COP displacement. These results suggest that the measurement of both lateral COP displacement during sitting and spinal curvature would be useful in predicting the risk of falling in PD patients.

It is believed that static balance undergoes changes in children with cerebral palsy (CP). Thus, we analyzed postural oscillation in 19 children with the aim of comparing balance between healthy children and those with CP. The sample was divided into two groups--one with 10 children diagnosed with diparetic CP (CPG) and a control group (CG) with nine healthy children, all capable of remaining in an orthostatic position without support and obeying spoken commands. The assessment of postural oscillation was performed with the children barefoot, arms alongside the body and looking toward a fixed point while standing on an unrestricted base for the feet. Data collection was performed using a TEKScan force platform with 30-second duration for each condition. The children had an average age of 7.9 years (+/- 2.07) in the CPG and 7.5 years (+/- 1.58) for the CG. Postural oscillation data in the anterior-posterior and medial-lateral directions were analyzed using the Data Analysis and Technical Graphics Origin 6.0 program. Statistical analysis of the mean oscillation value in the conditions of eyes open and eyes closed did not differ significantly between groups. However, there was a significant difference in mean anterior-posterior oscillation between groups (p = 0.00). The groups behaved similarly with regard to the visual deprivation. We conclude that children with CP exhibit less postural oscillation in comparison to healthy children under the same conditions.

This study used a within-subjects design. The purpose of this study was to examine cross-talk among monopolar surface electromyographic (EMG) signals from the superficial quadriceps femoris muscles. The "efficiency of electrical activity" technique for assessing muscle function uses monopolar EMG. Thus, knowledge of the potential for cross-talk among the superficial quadriceps femoris muscles when using monopolar recording will be valuable in rehabilitative settings. Fourteen healthy men (mean +/- SD age = 22.0 +/- 3.9 years) volunteered to perform submaximal to maximal isometric muscle actions of the dominant leg extensors in 10% increments from 10% to 100% of the maximum voluntary contraction (MVC). During each muscle action, monopolar surface EMG signals were detected from the superficial quadriceps femoris muscles. Three separate cross-correlations were performed to examine cross-talk among the vastus lateralis and rectus femoris, vastus medialis and rectus femoris, and vastus lateralis and vastus medialis. The peak cross-correlation coefficients ranged from R(x,y) = 0.182-0.944, with the greatest cross-talk occurring between the vastus lateralis and vastus medialis. In addition, the cross-correlation coefficients generally increased with force. These findings showed moderate to large degrees of crosstalk among monopolar surface EMG signals from the superficial quadriceps femoris muscles. Thus, the monopolar EMG signals from these muscles should be interpreted carefully and with the understanding that at least a portion of the signal from each muscle is due to cross-talk.