F-wave Measurements Research Articles

Effects of action observation and motor imagery of walking on the corticospinal and spinal motoneuron excitability and motor imagery ability in healthy participants.

Action observation (AO) and motor imagery (MI) are used for the rehabilitation of patients who face difficulty walking. Rehabilitation involving AO, MI, and AO combined with MI (AO+MI) facilitates gait recovery after neurological disorders. However, the mechanism by which it positively affects gait function is unclear. We previously examined the neural mechanisms underlying AO and MI of walking, focusing on AO+MI and corticospinal and spinal motor neuron excitability, which play important roles in gait function. Herein, we investigated the effects of a short intervention using AO+MI of walking on the corticospinal and spinal motor neuron excitability and MI ability of participants. Twelve healthy individuals participated in this study, which consisted of a 20 min intervention. Before the experiment, we measured MI ability using the Vividness of Movement Imagery Questionnaire-2 (VMIQ-2). We used motor evoked potential and F-wave measurements to evaluate the corticospinal and spinal motor neuron excitability at rest, pre-intervention, 0 min, and 15 min post-intervention. We also measured corticospinal excitability during MI of walking and the participant’s ability to perform MI using a visual analog scale (VAS). There were no significant changes in corticospinal and spinal motor neuron excitability during and after the intervention using AO+MI (p>0.05). The intervention temporarily increased VAS scores, thus indicating clearer MI (p<0.05); however, it did not influence corticospinal excitability during MI of walking (p>0.05). Furthermore, there was no significant correlation between the VMIQ-2 and VAS scores and changes in corticospinal and spinal motor neuron excitability. Therefore, one short intervention using AO+MI increased MI ability in healthy individuals; however, it was insufficient to induce plastic changes at the cortical and spinal levels. Moreover, the effects of intervention using AO+MI were not associated with MI ability. Our findings provide information about intervention using AO+MI in healthy individuals and might be helpful in planning neurorehabilitation strategies.

Optimal stimulation site of the femoral nerve to record F waves from the vastus lateralis muscle.

The conventional recording of F waves from the vastus lateralis muscle (VL) may not accurately measure the F-wave amplitude, as the F-wave latency is short and overlaps with the M wave. However, the optimal stimulation site of the femoral nerve for recording M and F waves separately from the VL remains unclear. In this study we aimed to determine the optimal stimulation site of the femoral nerve to record M and F waves separately from the VL. Stimulating electrodes were placed medial and lateral to the VL (50%, 60%, 70%, and 80% of the distance along a line extending from the proximal to the distal thigh). Each site of the distal thigh was electrically stimulated at random and F waves were recorded from the VL. Each stimulation site was considered to be success if there was no severe pain or discomfort during electrical stimulation of the femoral nerve and no overlap between the recorded M and F waves; otherwise, it was determined as a failure. Thirteen healthy men participated in the study. F waves were successfully recorded in five participants at the 50% sites, eight participants at the 60% site, and 12 participants at the 70% and 80% sites. In cases of failed F-wave measurement, the participants experienced severe pain or discomfort due to electrical stimulation. M and F waves could be recorded separately from the VL when the relevant branch of the femoral nerve was stimulated in the distal thigh.

Клинико-электронейромиографический алгоритм топической диагностики синдрома мышечной гипотонии у детей раннего возраста

Study Objective: To develop a clinical electroneuromyography (ENMG) protocol based on routine electromyography (EMG), standardization of needle EMG, and EMG parameters of the suprasegmental structures, for localization diagnosis of hypotonia syndrome (HS) in young children. Study Design: This was a comparative prospective study. Materials and Methods: One hundred and twenty-three patients, aged 1 month to 3 years, with HS of various origin underwent clinical examination and EMG. The following techniques were used for localization diagnosis by ENMG: surface EMG, needle EMG, measurement of nerve conduction velocity in peripheral motor and sensory nerves in the upper and lower limbs, F-wave measurement, and rhythmic stimulation. Study Results: The authors evaluated the possibility of describing suprasegmental disorders using the following parameters: F-wave monomorphism, myotatic reflex, and amplitude of voluntary muscular contractions. They proposed a clinical ENMG protocol for localization diagnosis of HS and a pediatric protocol for needle EMG; these approaches increased the rate of detecting HS up to 90-100%. They also developed a pediatric linear protocol for needle EMG to differentiate between myogenic and central HS. Conclusion: The study results demonstrated the high diagnostic value of ENMG-based differential diagnosis of HS, relying on the proposed protocols and on parameters indicating the condition of the suprasegmental structures. Keywords: neuromuscular disorders, hypotonia syndrome, electroneuromyography, diagnostic protocol, young children.

Modified ischaemic nerve block of the forearm: use for the induction of cortical plasticity in distal hand muscles.

Ischaemic nerve block (INB) of the forearm rapidly reduces somatosensory input to a part of the body, which leads to the functional reorganization of the temporarily deafferented primary motor cortex (M1). We applied a novel modified INB (mINB) to the forearm, maintaining mean blood pressure, to assess cortical plasticity in the primary somatosensory cortex (S1) and the M1 regions associated with small hand muscles. S1 excitability was measured by median nerve somatosensory-evoked potentials (SEPs), while M1 excitability was evaluated by motor-evoked potentials (MEPS), using transcranial magnetic stimulation. The finding that S1 excitability increased and M1 excitability decreased after the mINB was removed reflects the differential short-term cortical plasticity of the S1 and M1 regions. These opposite effects observed for the S1 and M1 regions following the mINB may indicate a possible intra-hemispheric interaction between the S1 and M1 regions. Ischaemic nerve block (INB) causes short-term sensory deprivation, leading to functional reorganization in the deafferented motor cortex (M1). We used a modified INB (mINB) to evaluate cortical plasticity in the somatosensory cortex (S1) and M1 region associated with small hand muscles, because INB strongly inhibits muscles distal to the tourniquet. Thirty-three healthy adults participated in different combinations of four experiments. A pneumatic tourniquet was placed just below the right elbow and inflated to induce a mINB. We recorded the median nerve somatosensory- and motor-evoked potentials (SEPs and MEPs) before, during and after mINB placement and assessed spinal cord excitability using F-wave measurements. SEPs at Erb's point (N9) were abolished during the mINB; those at cortical N20 were suppressed. After removing the mINB, N20 amplitudes increased significantly, while those at N9 did not fully recover. P14 amplitudes after tourniquet deflation immediately recovered to baseline levels. M1-MEP amplitudes decreased during the mINB, and Erb-MEPs were suppressed. After the mINB was removed, M1-MEPs remained suppressed, while Erb-MEPs fully recovered. F-waves were not affected by the intervention. Therefore, sensory, but not motor, nerve function was affected by the mINB. S1 excitability was enhanced after the mINB was removed, indicating that S1 and M1 excitability were modulated in opposing directions after deflation. These after-effects may reflect isolated effects or interactions between the S1 and M1 regions. Our findings may facilitate improved understanding of the sensorimotor modulations that occur distal to the tourniquet due to temporal deafferentation and lead to development of novel neuromodulation protocols.

Stimulus-induced repetitive discharge in F-wave measurement in nerve conduction studies

Stimulus-induced repetitive discharge in F-wave measurement in nerve conduction studies

Clinical application of movement observation using F-wave measurements

Clinical application of movement observation using F-wave measurements

Polyneuropathy associated with chronic hemodialysis: Clinical and electrophysiological study.

To estimate the frequency and pattern of peripheral polyneuropathy (PNP) that may affect patients maintained on hemodialysis. The study was carried out on 60 middle-aged male patients attending the Internal Medicine Department for maintenance hemodialysis. All were subjected to a complete neurological examination. Motor and sensory nerve conduction studies of both lower limbs (the tibial, peroneal and sural nerves) and both upper limbs (median and ulnar nerves), as well as F-wave measurements of both tibial and median nerves, were done. The patients were subdivided clinically into two groups, clinically apparent neuropathy and inapparent groups. Then they were divided according to the types of peripheral neuropathy detected by electrophysiological studies into axonal, demyelinated and mixed polyneuropathy. In addition, they were divided into motor, sensory and sensorimotor groups. Polyneuropathy was found clinically presented in 33 (55%) cases, while evident by electrophysiological examination in 100% of the clinically apparent group (33 patients) and evident in 92.5% of the clinically inapparent group (27 patients). The frequency of pathologic electrophysiological parameters was significantly higher in patients with longer duration of hemodialysis. Axonal polyneuropathy is the most prevalent type in those patients. Peripheral polyneuropathy is a common presentation in patients maintained on hemodialysis. The longer the duration of hemodialysis, the more liability to develop PNP that can be detected earlier by electrodiagnostic studies in the subclinical cases.

Influence of motor imagery of isometric flexor hallucis brevis activity on the excitability of spinal neural function

Purpose: This study aimed to validate the preliminary steps of motor image voluntary training in patients who are prone to falling as toe flexion muscle strength decreases.Materials and methods: We recorded the F-wave in 30 healthy subjects (20 men, 10 women; mean age, 22.5 ± 2.1 years). First, in a resting condition, the muscle was relaxed during the F-wave recording. Subsequently, the motion of the left flexor hallucis brevis muscle is photographed. F-waves were recorded immediately and at 5, 10, and 15 min after motor imagery. The amplitude of the F/M ratio and persistence were measured. The intervention group watched the exercise task video used for F-wave measurement daily for 1 month, whereas the non-intervention group did not. The second measurement was performed 1 month later in each group.Results: In the first measurement of the amplitude of the F/M ratio in both intervention and non-intervention groups, the image condition was significantly increased compared with the resting condition, but there was no significant difference in persistence. A significant decrease in the amplitude of the F/M ratio after image conditioning was observed in the second measurement of the intervention group.Conclusion: Although spinal nerve function excitement was enhanced during motor imagery, movement suppression was promoted, and spinal nerve excitability was suppressed when repeating the simple task. In the future, gradually upscaling the difficulty level of the toe flexion motor task used in the motor image may be necessary to prevent falls.

Acupuncture Increases the Excitability of the Cortico-Spinal System in Patients with Chronic Disorders of Consciousness Following Traumatic Brain Injury.

To evaluate the immediate effect of acupuncture on cortico spinal tract (CST) activity in patients with chronic disorders of consciousness (DOC) after traumatic brain injury (TBI) by measuring motor-evoked potential (MEP) using transcranial magnetic stimulation (TMS). Changes in several variables in the acupuncture session were compared with those in the control session without acupuncture in the same patients. Chubu Medical Center for Prolonged Traumatic Brain Dysfunction, Gifu, Japan. Fourteen patients (mean age ± standard deviation, 39 ± 17 years; 12 men) with chronic DOC (5 in a vegetative state and 9 in a minimally conscious state) following severe TBI. Acupuncture treatment was performed at GV 26, Ex-HN 3, bilateral LI 4, and ST 36 for 10 minutes. Main outcome measure was MEP amplitude. MEP amplitude, measured by using TMS on the primary motor cortex, was recorded from the abductor pollicis brevis muscle. MEP recordings were performed before acupuncture (baseline), 10 minutes after needle insertion (phase 1), and 10 minutes after needle removal (phase 2). As a control, the same procedure without acupuncture was performed on another day with the order randomized. MEP amplitude and latency were calculated. Evoked F-wave measurements were also performed to calculate maximum M-wave amplitude (Mmax), M-wave latency, and F-wave latency in the same muscle. Central motor conduction time (CMCT) and MEP/Mmax ratio were also calculated from the MEP and F-wave measurement data. MEP amplitude and MEP/Mmax were increased significantly in the acupuncture session at phases 1 and 2 compared with the control session (p < 0.001, p < 0.001, p < 0.001, and p = 0.001, respectively). CMCTs were reduced at phases 1 and 2 in the acupuncture session compared with the control session, and the change at phase 1 was statistically significant (P = 0.002). Acupuncture treatment increased the CST activity of patients with chronic DOC after severe TBI.

P31-7 F-wave measurements detect beneficial effects of high-intensity repetitive stimulation of the tibial nerve on neurogenic claudication in LSS

P31-7 F-wave measurements detect beneficial effects of high-intensity repetitive stimulation of the tibial nerve on neurogenic claudication in LSS

8. Pitfalls of f-wave measurements in critical care units

8. Pitfalls of f-wave measurements in critical care units

P078 Insights in electrophysiologic assessment of neuromuscular disorders associated with failure to wean from the ventilator: pitfalls of F-wave measurements

P078 Insights in electrophysiologic assessment of neuromuscular disorders associated with failure to wean from the ventilator: pitfalls of F-wave measurements

The Sensitivity of Clinical Diagnostic Methods in the Diagnosis of Diabetic Neuropathy

This study assessed the sensitivity of various methods for the clinical diagnosis of diabetic peripheral neuropathy. A total of 147 randomly selected patients with diabetes mellitus and 65 age- and sex-matched healthy controls were evaluated by various clinical (the neuropathy symptom score [NSS], the neuropathy disability score [NDS], vibration perception thresholds [VPTs], Tinel's sign and Phalen's sign), laboratory (fasting plasma glucose and glycosylated haemoglobin levels) and electro-physiological (nerve conduction studies, H-reflex and F-wave measurements) methods. In the patient group, 8.2% had an abnormal NSS, 28.5% had a positive Phalen's sign, 32.6% had a positive Tinel's sign, 42.8% had an abnormal VPT and 57.1% had an abnormal NDS. Significant correlations were found between electro-physiologically confirmed neuropathy and the two provocation tests and abnormal VPTs. In conclusion, assessment with a complete neurological examination and standard electrophysiological tests is very important for the diagnosis of diabetic peripheral neuropathy and the prevention of morbidity in patients with or without symptoms.

Factors influencing F-wave latency detection of lumbosacral root lesions using a detection theory based model

ObjectiveTo evaluate the F-wave dilution hypothesis; which implies that absolute F-wave latencies obscure the much smaller delay associated with slow intra-lesion conduction, such is caused by nerve root compression in lumbosacral radiculopathy. A corollary objective is to determine how F-wave measurement and pathological factors influence diagnostic accuracy. MethodsAn analytical model is developed based on signal detection theory and a number of simplifying assumptions. Diagnostic accuracy, quantified by the area under the receiver operating characteristic (ROC) curve, is determined for various model realizations derived from the clinical and experimental neurophysiology literature. A preliminary experimental validation of model predictions is also performed. ResultsAbsolute F-wave latency does not influence the accuracy of focal lesion detection. F-wave latency variance and lesion pathology are the determinant factors. F-wave latencies and distal latencies are estimated to have qualitatively similar detection characteristics, although distal latencies have quantitatively better diagnostic efficacy for comparable focal pathology. Preliminary experimental results support the modeled dependence of diagnostic accuracy on latency variance and lesion severity. ConclusionsAbsolute F-wave latency does not dilute slow conduction within focal lesions, such as in lumbosacral radiculopathy. The dominant measurement factor is F-wave latency variance. SignificanceTo maximize the diagnostic utility of F-wave latencies, focus must be placed on reducing latency variance, such as through correction for demographic covariates. This model calls into question the F-wave dilution hypothesis.

Long Cervical Costae Articulating with the First Ribs: A Salient Case of Thoracic Outlet Syndrome

The complex of signs and symptoms caused by compression of brachial plexus and subclavian vessels in the cervicoaxillary region is known as thoracic outlet syndrome (TOS).1 Bones and the surrounding soft tissues may play an important role in its pathogenesis. Bony factors include the long transverse process of the seventh cervical vertebra, a cervical rib, an anomalous first rib, or fractures of the clavicle or first rib.2 The most common symptoms of TOS patients are pain and paresthesias in the supraclavicular, interscapular, subscapular, and cervical regions or in the upper limbs. Although less common, some patients also experience tachycardia, dyspnea, dysphagia, angina-like chest pain, occipital headache, Raynaud's phenomenon, or complex regional pain syndrome.2–4 The diagnosis of TOS is established clinically when relevant complaints of the patients are provoked during maneuvers such as Adson, costoclavicular, hyperabduction, or Roos tests. Radiologic evaluations may shed light on the underlying pathogenesis, and cervical radiographs are simply the initial step in this regard. More sophisticated tools such as Doppler sonography, magnetic resonance imaging/angiography, and three-dimensional computed tomography can also be used for further assessment. Herein, besides presenting a rare, interesting articulation bilaterally between the cervical costae and the first ribs in a patient with TOS, we highlight the importance of oblique cervical radiographs for better delineation of such deformities. A 44-yr-old man was seen for numbness and a tingling sensation in his hands that had persisted for 3–4 mos. Physical examination revealed ulnar hypoesthesia on the left side, and provocative maneuvers for TOS (Roos and costoclavicular) were bilaterally positive. Laboratory evaluations for neuropathies and electrodiagnostic studies including median and ulnar nerve motor/sensory conduction tests, F-wave measurements, and medial antebrachial nerve conduction tests were unremarkable. Cervical radiographs were taken as the initial step for radiologic diagnosis and evaluation. Posteroanterior views suggest an anomalous cervical rib (Fig. 1A), and oblique views clearly demonstrate bilateral long cervical costae (Fig. 1B). He was diagnosed to have TOS clinically—with regard to his symptoms and physical findings—and radiologically due to the aforementioned anomalies in the cervical region. Because he was decided to be treated conservatively, a home-based exercise regimen for strengthening the shoulder elevators was prescribed. He was found to have improved clinically on the first control visit after 3 mos.FIGURE 1: A, posteroanterior cervical radiograph depicting bilateral cervical costae articulating with the first ribs; B, right cervical radiograph (oblique view) clearly delineating the articulation

Differentiation of spinal and cerebral effects of anaesthetics in humans using clinical electrophysiology techniques

From animal studies, it is known that the suppression of motor reactions after painful stimuli, i.e., the MAC, is mediated at a subcortical site. To confirm these findings in humans, we studied the concentration-dependent effect of sevoflurane and propofol on electrophysiological parameters derived from either the spinal cord (H-reflex and F-waves) or the cerebral cortex (EEG).A total of 161 patients were studied with either sevoflurane or propofol and either H-reflex or F-wave measurement. In parallel, EEG parameters were recorded. The hysteresis between anaesthetic concentration and effect was eliminated by calculating the time constant t1/2ke0 for equilibration between plasma and effect compartment, using pharmacokinetic–pharmacodynamic modelling.Equilibration time constants t1/2ke0 were much larger for spinal parameters than for the EEG parameters, both for sevoflurane and propofol. For sevoflurane, the concentration–response curve for H-reflex suppression was similar to the logistic regression curve for suppression of movement, whereas F-waves were suppressed at much lower concentrations.The differences in equilibration time constants between EEG parameters and spinal parameters are in line with the findings in animal experiments that suppression of movement by anaesthetics occurs at a site distinct from those causing EEG alterations and presumably unconsciousness.

Motoneuron excitability and the F wave.

For three motoneuron pools that differ in excitability to Ia inputs [tibialis anterior (TA), abductor pollicis brevis (APB), and soleus], F-wave parameters were measured at rest, during voluntary contraction, and following prolonged vibration. There was an inverse relationship between F-wave chronodispersion and F-wave persistence at rest, and this appeared to be related to the ease of recording the H reflex for the motoneuron pool. During a steady voluntary contraction, overall F-wave activity increased in amplitude but decreased in duration for TA and APB. Following vibration of the test muscle at 50 HZ for 10 min there was a long-lasting depression of the H reflexes of TA and APB, but no significant change in F-wave measurements. These findings are consistent with the view that reflex discharges can prevent F waves in low-threshold motor units, and that chronodispersion is affected by the extent of reflex activity; that is, chronodispersion and related F-wave measurements do not measure motor properties exclusively. The findings also suggest that F waves provide a flawed measure of the excitability of the motoneuron pool.

Hemispheric asymmetry of ipsilateral motor cortex activation during unimanual motor tasks: further evidence for motor dominance

Objectives: To test to which extent the increase in ipsilateral motor cortex excitability during unimanual motor tasks shows hemispheric asymmetry. Methods: Six right-handed healthy subjects performed one of several motor tasks of different complexity (including rest) with one hand (task hand) while the other hand (non-task hand) was relaxed. Focal transcranial magnetic stimulation was applied to the motor cortex ipsilateral to the task hand and the amplitude of the motor evoked potential (MEP) in the non-task hand was measured. In one session, the task hand was the right hand, in the other session it was the left hand. The effects of motor task and side of the task hand were analyzed. Spinal motoneuron excitability was assessed using F-wave measurements. Results: Motor tasks, in particular complex finger sequences, resulted in an increase in MEP amplitude in the non-task hand. This increase was significantly less when the right hand rather than the left hand was the task hand. This difference was seen only in muscles homologous to primary task muscles. The asymmetry could not be explained by changes in F-wave amplitudes. Conclusions: Hemispheric asymmetry of ipsilateral motor cortex activation either supports the idea that, in right handers, the left motor cortex is more active in ipsilateral hand movements, or alternatively, that the left motor cortex exerts more effective inhibitory control over the right motor cortex than vice versa. We suggest that hemispheric asymmetry of ipsilateral motor cortex activation is one property of motor dominance of the left motor cortex.

F-waves in clinical neurophysiology: a review, methodological issues and overall value in peripheral neuropathies

This report comments on methodological issues related to the use of F-wave in clinical neurophysiology. An F-wave study aims to describe with relative accuracy the properties of the compound F-wave population which is the population of F-waves consecutively recorded from a muscle. This can only be achieved if an adequate number of F-waves is sampled. In order to avoid inaccuracies, correction of F-wave latency measurements for height or limb length and age is also required. Differences in the recording procedure could account for the variability in F-wave measurements. The usefulness of F-wave parameters other than latency is discussed. F-chronodispersion and F-tacheodispersion are more sensitive than conventional neurophysiological methods in detecting mild nerve lesions. F-persistence provides valuable information only if the findings are interpreted in correlation with the particular clinical setting. The suitability of the F-wave technique for routine studies is examined and a current view on the clinical applications is briefly recounted. There is an urgent need for the standardization of F-wave methodology.

The F-wave in the vastus lateralis M. and the segmental motor conduction times for [formula omitted] motoneurons

The study was performed in 30 normal subjects. Electrical stimulation was applied to the femoral nerves and the muscle evoked potential (CMAP) together with their late components were recorded from the vastus lateralis muscle bilaterally (60 nerves). Features of the late component demonstrating its antidromic nature (F-wave) were proved. Additionally, in each subject transcranial cortical (C) magnetic stimulation and root (Rx) magnetic stimulation at the level of the L3–L4 was applied. The measured latencies of respective motor evoked potentials C-MEP (relaxed muscles), CA-MEP (activated), Rx-MEP as well as the latencies of peripheral CMAP and F-wave allowed the calculation of the derived parameters, i.e. segmental times of motor conduction: central, root and peripheral. The normative values were established. The F-wave measurement also allowed for the calculation of the so-called real central conduction time, which proved to be significantly shorter than the corresponding times previously established for the lower situated L4 S1 motoneurons. This finding suggest usefulness of the method in the precise diagnosis of the lumbosacral spinal enlargement.