The usefulness of minimal F-wave latency and sural/radial amplitude ratio in diabetic polyneuropathy

The possibility of whether minimal F-wave latency and a simple ratio between the sural and superficial radial sensory response amplitudes may provide a useful electrodiagnostic test in diabetic patients was investigated in this report. To evaluate the diagnostic sensitivity of minimal F-wave latency, the Z-scores of the minimal F-wave latency, motor nerve conduction velocity (MCV), amplitude of compound muscle action potentials (CMAP), and distal latency (DL) of the median, ulnar, tibial, and peroneal nerve were compared in 37 diabetic patients. For the median, ulnar, and tibial nerves, the Z scores of the minimal F-wave latency were significantly larger than those of the MCV. In addition for all four motor nerves, the Z scores of the minimal F-wave latency were significantly larger than those for the CMAP amplitude. Furthermore, 19 subjects showing abnormal results in the standard sensory nerve conduction study had a significantly lower sural/radial amplitude ratio (SRAR), and 84% of them had an SRAR of less than 0.5. In conclusion, minimal F-wave latency and the ratio between the amplitudes of the sural and superficial radial sensory nerve action potential are sensitive measures for the detection of nerve pathology and should be considered in electrophysiologic studies of diabetic polyneuropathy.     

Diagnostic value of F-wave inversion in patients with early carpal tunnel syndrome

Routine electrophysiological studies usually give normal results in patients with early stage carpal tunnel syndrome (CTS). Diagnostic significance of the F-wave inversion (the median of F-wave minimal latencies (FWML) exceeds a normal ipsilateral ulnar FWML by 1 ms) has not been previously reported in early stage CTS. In this study, our primary aim was to investigate the diagnostic value of F-wave inversion in early stage CTS. Additionally, we aimed to demonstrate any possible relationship between F-wave inversion and symptom scores of the Boston questionnaire and functional capacity in early stage CTS. The study included 60 early stage CTS patients who presented with a median sensory nerve conduction velocity of ≥50 m/s. The symptom severity and functional status of the patients were assessed by using the Boston questionnaire. The control group consisted of 45 healthy volunteers. We compared early stage CTS patients and healthy control subjects in terms of the results obtained from median-ulnar FWML. Existence of F-wave inversion was found in 32 (53.3%) of the early stage CTS patients and in 3 (8.7%) of the healthy controls (p = 0.001). It was also found to be positively correlated with the Boston questionnaire scores (p = 0.001, r = 0.41) and functional capacity scores (p = 0.001, r = 0.41). The sensitivity and specificity of F-wave inversion for the diagnosis of early stage CTS were calculated as 53.3% and 93.3%, respectively. The addition of F-wave inversion measurement to the set of the routine nerve conduction studies can increase the reliability of the electrophysiological studies in patients with early stage CTS.     

Characteristic appearances of the H-reflex and F-wave with increased stimulus intensity in patients with cerebrovascular disease

We experienced H-reflex may be evoked with supramaximal stimulation in patients with cerebrovascular disease (CVD). In this study, we investigated the relationship between the characteristic appearances of H-reflex and F-wave with increased stimulus intensity and neurological signs. We examined the H-reflex and F-wave of the affected arm with increased stimulus intensity during muscle relaxation in 31 patients (17 males and 14 females) with hemiparesis caused by CVD. Mean patient age was 56.0 (range 30-82) years. 30 healthy subjects, mean age of 56.2 (range 28-80) were investigated using the same method as controlled group. H-reflex and F-wave with increased stimulus intensity after the median nerve stimulation at the wrist were recorded from the opponence pollicis muscle on the affected side in patients with CVD or right arm in the healthy subjects. Appearance patterns of the H-reflex and F-wave with increased stimulus intensity was separated into four types. Type 1: F-wave appeared with increased stimulus intensity, but there was no H-reflex. Type 2: H-reflex and F-wave both appeared with increased stimulus intensity, but the F-wave followed disappearance of the H-reflex with increased stimulus intensity. Type 3: H-reflex and F-wave both appeared with increased stimulus intensity, but the F-wave appeared during the H-reflex with increased stimulus intensity. Type 4: Only the H-reflex appeared with increased stimulus intensity, but there was no F-wave. Neurological findings including muscle tone and tendon reflex were also evaluated. Findings on muscle tone and tendon reflex were classified into increased (markedly, moderately and slightly), normal and decreased. Results were analyzed as follows; 1) The characteristic appearances of H-reflex and F-wave in the healthy subjects and 2) The relationship between characteristic appearances of waves with increased stimulus intensity and neurological signs in patients with CVD. 1) Pattern of the H-reflex and F-wave with increased stimulus intensity in all healthy subjects were type 1. 2) Patterns of the H-reflex and F-wave with increased stimulus intensity in patients with markedly increased muscle tone and tendon reflex were almost always type 4. Those with moderately increased signs in this parameter demonstrated type 2 or 3. Those with slightly increased signs in this parameter demonstrated type 1 or 2. Those with normal or decreased signs were type 1. These findings suggest that the characteristic appearances of the H-reflex and F-wave was influenced by grade of neurological signs.     

Acute brachial neuropathy--electrophysiological study and clinical profile.

Acute brachial neuropathy (ABN) is a rare disease, characterized by an acute or subacute onset of pain followed by weakness of shoulder or arm muscles without trauma or traction injury. So the diagnosis of this clinical entity is not easy. The purpose of this study was to analyze retrospectively the ABN in 14 cases focusing on the clinical profile and to evaluate the effectiveness of electrophysiologic study in diagnosis of ABN with a new result helpful in localizing a brachial plexus disorder. The most helpful electrophysiologic data of ABN in my patients seemed to be abnormalities of low amplitude, abnormal right to left difference of compound motor action potentials (CMAPs) and sensory nerve action potentials (SNAPs) in axillary nerve, ulnar or median nerves. Results of nerve conduction velocity, terminal and F-wave latency were not as useful. But the electromyogram was most helpful in localization of upper or lower plexus lesions and cervical radiculopathy. The most striking clinical feature of ABN was the rapid onset of pain followed by the development of muscle weakness of shoulder girdle after a variable period or within four days. In contrast to other reports, intrinsic hand muscle weakness was observed in 3 cases with sensory changes in ulnar nerve distribution. The cervical radiculopathies (C5-C7 roots) were simultaneously combined with ipsilateral axillary neuropathy in 3 cases. In this study, decreased amplitude, abnormal right to left difference of SNAPs and CMAPs, and neurogenic EMG findings with normal data of NCV, terminal and F-wave latencies suggest that the pathology of ABN might not be a demyelinating process, but axonopathy.     

Current perception threshold: an adjunctive test for detection of acquired demyelinating polyneuropathies

Current Perception Threshold (CPT) evaluation quantifies the sensory threshold to transcutaneous electrical stimulation of three sensory fiber subtypes: A-beta (2,000 Hz), A-delta (250 Hz) and C fibers (5 Hz). Demyelinating polyneuropathies tend to affect larger myelinated fibers before smaller unmyelinated fibers, and they usually begin at the proximal nerve roots or terminal axons, due to relative weakness of the blood-nerve barrier in these locations. Axonal polyneuropathies tend to affect smaller fibers before larger fibers, in a distal to proximal gradient. Ten patients with demyelinating polyneuropathy and ten patients with axonal polyneuropathy underwent CPT testing. CPT comparisons were made with regard to side-to-side asymmetries, fiber type involvement, and the ratio of fiber types involved. The C2, lateral antebrachial cutaneous, and sural distributions were examined bilaterally. Demyelinating polyneuropathies were detected with 50% sensitivity and 100% specificity. This diagnostic sensitivity is similar to that of published criteria based upon motor nerve conduction. CPT testing can distinguish demyelinating from axonal polyneuropathies. It may be particularly helpful in patients with predominantly sensory symptoms in whom EMG/NCS data may be equivocal, or in patients who decline EMG/NCS studies.     

磁刺激运动诱发电位对S_1神经根病的诊断价值

采用磁刺激腰骶部运动神经传导时间（ＭＮＣＴ）与磁刺激窝Ｆ波相结合测定运动神经根传导时间（ＭＲＣＴ）的方法，无痛无创地评估Ｓ１神经根功能。研究对象为５０名正常受试者和３０名Ｓ１神经根受损病人。结果表明：磁刺激ＭＮＣＴ在病人组均正常，而ＭＲＣＴ却明显异常，异常率为８７％，明显高于Ｆ波潜伏期的异常率７３％。因此，磁刺激运动诱发电位（ＭＥＰ）是诊断Ｓ１神经根病的一种有很大应用价值的方法。     

Electrophysiologic evaluation of beri-beri polyneuropathy

The diagnostic utility of electroneuromyography including F-wave and H-reflex was studied in 68 patients with peripheral polyneuropathy due to nutritional deficiency of thiamine. Out of all the electrophysiologic evaluations assessed, denervation activity in electromyography, prolonged conduction velocity and reduced motor nerve action potentials and prolonged H-reflex latency were the most frequently found abnormal findings, followed by reduced sural nerve action potential and, much less frequently, prolonged F-wave latency. In experimental thiamine-deficiency evoked polyneuropathy in chickens, the prominent abnormal findings were found in the leg muscles such as F-wave pathology and reduction and prolongation of peroneal and sciatic motor nerve action potentials, and also a prolongation of the distal sensory peroneal nerve latency respectively.     

Diagnostic value of extensor digitorum brevis F-wave in L5 root compression

The sensibility of F-wave in detecting lumbosacral radicular compression has been found to range from 65% to 18%. The present study was performed on 24 patients suffering from unilateral L5 compressive radiculopathy. The aim was to verify the reliability of extensor digitorum brevis (EDB) F-wave in the diagnosis of L5 root impairment, by using different parameters such as minimal, mean, maximal latency and the difference of these parameters between the affected and unaffected sides. In all patients conventional needle EMG was also performed bilaterally. While the needle EMG showed abnormalities in L5 innervated muscles of all patients, at least one of the different EDB F-wave parameters was found to be abnormal in only 7 patients (29.2%). Moreover no significant relation was observed between the severity of EMG and F-wave abnormalities. We conclude that conventional needle EMG appears to be the most useful electrophysiological technique in the diagnosis of L5 compressive radiculopathy, while EDB F-wave does not provide additional information.     

Single motor unit F-waves in the thenar muscles studied by the multichannel surface EMG

The thenar motor units (MUs) were studied by the multichannel surface electromyography (EMG) technique. The median nerve was stimulated at the wrist by repetitive submaximal stimulation. Three hundred consecutive evoked responses were recorded from the thenar muscles of 5 healthy volunteers with a 32 channel matrix-type multielectrode. Seven channel F-wave waveforms in a selected electrode array were classified using a template-matching method. The F-wave parameters, amplitudes, latencies and muscle fiber conduction velocities (MFCVs), were calculated to evaluate the properties of single MU F-wave. Most of the F-waves (93.3%) were composed of a single motor unit action potential (MUAP). The numbers of MU classified from single MU F-waves in 5 subjects were 11, 8, 13, 13 and 13, respectively. Many of them (84.5%) were originated from the abductor pollicis brevis (APB), and there were a few MUs originated from the flexor pollicis brevis (FPB). Significant correlations were found between F-wave amplitudes and latencies in 3 subjects.     

F wave measurements detecting changes in motor neuron excitability after ischaemic stroke

OBJECTIVE: To study mechanisms that are involved in the hyperexcitability of spinal motor neurons in upper motor neuron lesion, by means of F-wave measurements. METHODS: F waves from 44 hospitalized stroke patients and 35 healthy controls were recorded from abductor pollicis brevis muscles in the course of two experiments: (1) single stimuli following high-intensity ipsilateral cutaneous conditioning were used to stimulate the median nerve; (2) paired stimuli were given to the median nerve at gradually increasing interstimulus intervals to assess recovery curves. Mean F-wave amplitudes elicited by the conditioning stimuli were compared with mean F-wave amplitudes elicited by the test stimuli on both the hemiparetic and the unaffected side. RESULTS: There was no reduction on the hemiparetic side of mean F-wave amplitudes elicited following high-intensity ipsilateral cutaneous stimulation. The recovery of mean F-wave amplitude was completed at longer interstimulus intervals on the hemiparetic side than on the unaffected side and in controls. A correlation was found between this delay of recovery and hemiparetic severity. CONCLUSIONS: The results of our study support the role of changes in lower motor neuron membrane excitability in the enhancement of F wave amplitudes after stroke.     

合并移行椎腰椎间盘突出症患者腰骶神经根支配区的变化

背景:腰骶移行椎是一种常见的先天脊柱畸形,国内外学者均有报道移行椎患者的腰骶神经根支配I区可能会发生改变,但并未系统阐述其支配区的变化以及该种改变对腰椎间盘突出症患者手术的指导意义。目的:探讨当存在腰骶移行椎时,腰骶神经根的运动和感觉支配区发生改变的可能性。方法:研究方案的实施符合滨州医学院附属医院对研究的相关伦理要求,参与试验的患病个体及其家属对试验过程完全知情同意。回顾分析321例单一节段腰椎间盘突出症行手术治疗患者的病历资料。其中38例(11.8%)存在腰骶移行椎,包括骶椎腰化26例、腰椎骶化12例。26例骶椎腰化患者中,23例为L5/S1(L6)椎间盘突出,压迫S1(L6)神经根。12例腰椎骶化患者中,8例为L3/4椎间盘突出,压迫L4神经根。在283例正常结构的患者中,138例患者L5/S1椎间盘突出压迫S1神经根,95例患者L4/L5椎间盘突出压迫L5神经根,47例患者L3/L4椎间盘突出压迫L4神经根。比较术前骶椎腰化患者S1神经根受压的症状、腰椎骶化患者L4神经根受压的症状与正常腰骶椎患者L4、L5或S1神经根受压的症状。结果与结论:(1)S1神经根受压所致运动功能减退的分布在骶椎腰化患者组和正常组之间差异有显著性意义(P<0.05);(2)L4神经根受压所致运动功能减退的分布在腰椎骶化患者组和正常组之间差异有显著性意义(P<0.05);(3)骶椎腰化患者S1神经根受压所致的运动功能减退与正常状态下L5神经根受压所致的运动功能减退相似;而腰椎骶化患者L4神经根受压所致的运动功能减退与正常状态下L5神经根受压所致的运动功能减退相似;皮肤感觉异常的分析也显示了相似的结果;(4)结果说明,腰骶神经根的功能在移行椎患者中发生改变,使得骶椎腰化患者的S1神经根起到L5神经根的通常功能(神经根功能上移),腰椎骶化患者的L4神经根起到L5神经根的通常功能(神经根功能下移)。     

Riluzole suppresses motor cortex facilitation in correlation to its plasma level

The aim of our study was to measure the effects of the glutamate antagonist riluzole on different parameters of motor excitability, using transcranial magnetic stimulation (TMS) during 7 days of riluzole administration, and to correlate these effects with riluzole plasma levels. Nine healthy volunteers received a dose of 100 mg riluzole from day 1 to 7 of the study period. Electrophysiological examinations were performed on day 1 before and 2 h, 5 h and 8 h after riluzole administration, on day 2, day 3 and day 5 before riluzole administration, and on day 8. Plasma samples were taken simultaneously. The excitability of the motor cortex, supraspinal and spinal motor pathways was tested by studying intracortical facilitation and inhibition, the cortical silent period and motor threshold after TMS, as well as the peripheral silent period and F-wave amplitudes after electrical peripheral nerve stimulation. We found a significant reduction of intracortical facilitation, which correlated significantly with riluzole plasma levels. To a lesser extent, intracortical inhibition was enhanced on day 1, motor threshold was increased on day 8 and F-wave amplitudes were reduced. These changes did not correlate with riluzole plasma levels. We conclude that the main effect of riluzole in vivo is a reduction of intracortical facilitation, which is closely related to the drug's level in the plasma. The most probable mechanism involves an effect on glutamatergic synaptic transmission.     

Modulation of motor cortex excitability by median nerve and digit stimulation

We investigated the time course of changes in motor cortex excitability after median nerve and digit stimulation. Although previous studies showed periods of increased and decreased corticospinal excitability following nerve stimulation, changes in cortical excitability beyond 200 ms after peripheral nerve stimulation have not been reported. Magnetoencephalographic studies have shown an increase in the 20-Hz rolandic rhythm from 200 to 1000 ms after median nerve stimulation. We tested the hypothesis that this increase is associated with reduced motor cortex excitability. The right or left median nerve was stimulated and transcranial magnetic stimulation (TMS) was applied to left motor cortex at different conditioning-test (C-T) intervals. Motor-evoked potentials (MEPs) were recorded from the right abductor pollicis brevis (APB), first dorsal interosseous (FDI), and extensor carpi radialis (ECR) muscles. Right median nerve stimulation reduced test MEP amplitude at C-T intervals from 400 to 1000 ms for APB, at C-T intervals from 200 to 1000 ms for FDI, and at C-T intervals of 200 and 600 ms for ECR, but had no effect on FDI F-wave amplitude at a C-T interval of 200 ms. Left median nerve (ipsilateral to TMS) stimulation resulted in less inhibition than right median nerve stimulation, but test MEP amplitude was significantly reduced at a C-T interval of 200 ms for all three muscles. Digit stimulation also reduced test MEP amplitude at C-T intervals of 200–600 ms. The time course for decreased motor cortex excitability following median nerve stimulation corresponds well to rebound of the 20-Hz cortical rhythm and supports the hypothesis that this increased power represents cortical deactivation. Received: 11 December 1998 / Accepted: 30 April 1999     

Sensory nerve somatosensory evoked potentials (SEP) in the evaluation of patients with sciatica: false P1 latency prolongation may be due to admixture of dermatomal SEP.

Patient-reported stimulus-related radiating sensory symptoms within the territory of the stimulated nerve have been used to verify stimulation in sensory nerve scalp recorded somatosensory evoked potentials (SEP). The main aim of the present study of false positive P1 latency prolongation in lumbosacral sensory nerve SEP was to investigate whether elicitation of such symptoms secures adequate sensory nerve stimulation. Nerve roots were studied on the asymptomatic side in 64 patients with unilateral sciatica. Saphenous (L4), superficial peroneal (L5), and sural (S1) nerve SEP were registered in all patients. Pretibial dermatomal SEP were registered in ten of them. Stimulation was equidistant from the registration electrode in all SEP registrations. The false positive rate was lower in saphenous nerve SEP with than without verified supramaximal stimulation (1/30 vs. 6/22, P = 0.03) in spite of radiating stimulus-related sensory symptoms in both groups. This difference was not caused by subclinical myelographic nerve root compression or general peripheral nerve dysfunction. The P1 latency was longer in the pretibial dermatomal SEP than in the saphenous and superficial peroneal nerve SEP with the same conduction distance (mean difference 4.7 (95% CI = 3.8 to 5.6) and 4.4 ms (95% CI = 3.4 to 5.4), respectively). It is concluded that dermatomal SEP have longer P1 latency than sensory nerve SEP. Verified supramaximal nerve simulation is recommended to avoid false results due to admixture of dermatomal to sensory nerve SEP.     

Electrophysiologic correlates of weakness in L5/S1 radiculopathy

INTRODUCTION: Management of patients with radiculopathy involves estimating the degree of physiologic and anatomic injury, and weighing that to predict the likely clinical course. OBJECTIVE: To determine whether low distal peroneal and tibial CMAP amplitudes correlate with weakness and fibrillations of functionally relevant muscles in L5/S1 radiculopathy (LSR). METHODS: We reviewed clinical and electrophysiologic data in 66 consecutive patients with LSR. RESULTS: A significantly greater number of patients with low peroneal CMAP amplitudes had weakness of L5 (p = 0.025) and S1 innervated leg muscles (p < 0.001). Low tibial CMAP amplitudes were also associated with weakness of S1 innervated muscles (p < 0.038). The association of low peroneal CMAP amplitudes with weakness persisted when weakness of at least 3 muscles was considered in the analysis for L5 (p < 0.0001) and S1 (p = 0.014) innervated muscles. CONCLUSIONS: Low peroneal and tibial CMAP amplitudes may serve as surrogate measures for segmental weakness of functionally relevant muscles in LSR.     

F-waves and conduction velocities range

A controversial aspect in F-wave studies is if these potentials are generated preferentially by large motoneuron or by motoneuron of all sizes. The purpose of this work is to compare the maximum and minimum conduction velocities of the fibers that generate the M-wave with the maximum and minimum conduction velocities of the F-waves elicited by ulnar nerve stimulation. There were no significant differences between maximum velocities. However, minimum F-wave velocity was significantly higher than minimum conduction velocity, suggesting that the F-waves registered were preferentially generated by the fastest conducting axons.     

Changes in muscle responses to stimulation of the motor cortex induced by peripheral nerve stimulation in human subjects

The aim of this study was to determine whether prolonged, repetitive mixed nerve stimulation (duty cycle 1 s, 500 ms on-500 ms off, 10 Hz) of the ulnar nerve leads to a change in excitability of primary motor cortex in normal human subjects. Motor-evoked potentials (MEPs) generated in three intrinsic hand muscles [abductor digiti minimi (ADM), first dorsal interosseous (FDI) and abductor pollicis brevis (APB)] by focal transcranial magnetic stimulation were recorded during complete relaxation before and after a period of prolonged repetitive ulnar nerve stimulation at the wrist. Transcranial magnetic stimuli were applied at seven scalp sites separated by 1 cm: the optimal scalp site for eliciting MEPs in the target muscle (FDI), three sites medial to the optimal site and three sites lateral to the optimal stimulation site. The area of the MEPs evoked in the ulnar-(FDI, ADM) but not the median-innervated (APB) muscles was increased after prolonged ulnar nerve stimulation. Centre of gravity measures demonstrated that there was no significant difference in the distribution of cortical excitability after the peripheral stimulation. F-wave responses in the intrinsic hand muscles were not altered after prolonged ulnar nerve stimulation, suggesting that the changes in MEP areas were not the result of stimulus-induced increases in the excitability of spinal motoneurones. Control experiments employing transcranial electric stimulation provided no evidence for a spinal origin for the excitability changes. These results demonstrate that in normal human subjects the excitability of the cortical projection to hand muscles can be altered in a manner determined by the peripheral stimulus applied.     

A study of diagnostic yield, technical ease and patient discomfort of low rate repetitive nerve stimulation test in patients with myasthenia gravis

AIM: The diagnostic yield of repetitive nerve stimulation (RNS) study in different muscles has been evaluated in myasthenia gravis (MG) but there is paucity of comprehensive study on technical ease and patient comfort. In this study we evaluate diagnostic yield of RNS test, technical ease and patient discomfort in 8 different muscles in patients with MG. METHODS: Consecutive patients with MG diagnosed on the basis of clinical evaluation, neostigmine test and/or acetylcholine receptor antibody (AchRAb) assay were subjected to 3 Hz RNS study in abductor digiti minimi (ADM), flexor carpi ulnaris (FCU), anconeus, deltoid, trapezius, serratus anterior (SA), nasalis and tibialis anterior (TA) at rest and 3 min after 30 s exercise. Decrement exceeding 10% was considered abnormal. Patient's discomfort was assessed on a 0-5 scale and technical difficulty by the number of repetitions needed to complete the test or abandonment of test. RESULTS: Thirty-three patients with MG whose age ranged between 16-81 y were evaluated. At the time of RNS study the predominant weakness was ocular in 3, oculobulbar in 13 and limb in 17 patients. The highest diagnostic yield of RNS test was with deltoid and nasalis (78.8% each), followed by trapezius (65.5%). The highest mean patient discomfort score was with deltoid (2.4), followed by nasalis (1.3). The technical difficulty was maximal in deltoid needing 36.4% repetitions followed by SA (33.3%). In oculobulbar group the best yield was in nasalis (92.3%) followed by deltoid (84.6%), and in limb variety deltoid (82.4%) followed by SA (80%) and trapezius (75%). Combining the diagnostic yield, patient comfort and technical ease; the choice of muscle for RNS should be ADM followed by trapezius for patient with predominant limb weakness, nasalis and trapezius in oculobulbar and nasalis in ocular.     

The diagnostic value of dermatomal somatosensory evoked potentials in lumbosacral disc herniations: a critical approach

In this study, we examined scalp recorded dermatomal somatosensory evoked potentials (DSEPs) to electrical stimulation of L4, L5 and S1 dermatomes in 55 patients with proven lumbosacral radiculopathy and in 22 healthy subjects. We did not observe any significant ipsilateral intertrial variations and arithmetic mean side-to-side differences in normal subjects. As for segmental latencies, the dermatomal P40 latencies were directly correlated with height. The regression equations for L4, L5 and S1 dermatomes were as follows: (L4) y = 5.8 + 21.3 (height), (L5) y = -2.09 + 28.04 (height), (S1) y = -13.9 + 36.4 (height). Maximum side-to-side latency differences and maximum P 40 latencies were obtained by adding 2 standard deviations to the arithmetic means. The abnormal latencies for L4, L5 and S1 dermatomes were 48 msec., 52 msec., and 55 msec., respectively. The abnormal side-to-side latency difference were 3 msec. for all dermatomes. DSEPs accurately predicted the lesion only in four patients (7.2%). In 20 patients (36.3%), DSEPs correctly identified the lesion but also gave misleading information on the other levels. DSEP abnormality were on the correct level but opposite side in 5 patients (9%). The findings were normal in 11 patients (20%), and misleading in 15 patients (27.2%). We conclude that the ultimate diagnostic utility of DSEPs in lumbosacral radiculopathies is doubtful and controversial needs further investigations.     

The effects of electrical nerve stimulation of the lower extremity on H-reflex and F-wave parameters

The main purpose of this study was to investigate the effects of electrical nerve stimulation on alpha motoneurons excitability. The electrophysiological parameters of H-reflex and F-wave were assessed for this object. These experiments was performed on ten non-athletic healthy men without neurologic disorders with mean age 25.6 years (SD 4.4) and three spastic hemiplegic patients with mean age 65.33 years (SD 6.32). In the experimental protocol, electrical stimulation (TENS) applied on common peroneal nerve with frequency 99 Hz and duration 0.25 ms for 30 minutes. H-reflex and F-wave of the soleus muscle were recorded in three stages sequenced immediately, 5 minutes and 10 minutes later on. The parameters such as amplitudes and latencies of H-reflex and F-wave were compared with the data of first record before stimulation. Finally, after 30 minutes application of TENS the following results were obtained: 1. The mean peak to peak amplitude of H-reflexes and F-waves were significantly decreased after application of TENS in normal subjects. (P < 0.05) 2. H/M ratios and F/M ratios were significantly decreased after application of TENS in normal subjects. (P < 0.05) 3. The mean latency of H-reflexes and F-waves were significantly increased after application of TENS in normal subjects. (P < 0.05) 4. In spastic patients, the mean peak to peak amplitude of H-reflexes and F-waves, H/M and F/M ratios were significantly decreased and the mean latencies of H-reflexes and F-waves were significantly increased after application of TENS. The reduction of amplitude of H-reflexes and F-waves, H/M and F/M ratios demonstrated reduction of spasticity in patients group. The above-mentioned parameters are parts of electrophysiological indicators about assessment of spasticity.