Central motor conduction studies in motor neurone disease using magnetic brain stimulation

Central motor conduction (CMC) to abductor digiti minimi (ADM) was evaluated in 22 patients with motor neurone disease (MND) using magnetic stimulation of the motor cortex and electrical stimulation at the C7/T1 interspace. CMC was abnormal in 14 patients; prolonged CMC time and absence of response to brain stimulation were more frequent abnormalities than low amplitude responses without prolonged CMC time. The technique can reveal subclinical upper motor neurone involvement and document central motor pathway dysfunction in MND. The patterns of abnormality are not specific to MND; all may occur in other neurological disorders including multiple sclerosis.     

Electrophysiological changes in diabetic neuropathy: from subclinical alterations to disabling abnormalities

Clinical spectrum of diabetic neuropathy is variable; it may be asymptomatic, but once established as polyneuropathy, it is irreversible and may finally be disabling. To estimate the prevalence of subclinical diabetic polyneuropathy in the UAE, we undertook a pilot study by means of nerve conduction study (NCS) of peroneal motor and sural sensory studies in 60 diabetics with no symptoms of neuropathy. Neurological examination revealed clinical abnormalities suggesting polyneuropathy in 26 patients, 43% of the patients. NCS revealed abnormal values in 63% of the whole patients. Abnormal NCS was confirmed in 88% of the positive sign group. As to the negative sign group 44% had abnormalities in NCS. Prolonged F-wave latency was seen in 29% in no sign group and in 66% of the patients with positive signs. We found close association between neurological deficit score and abnormalities in NCS. Among various parameter of systemic nerve conduction study in subclinical patients, prolonged F-wave latency seems the commonest abnormality suggesting morphological changes in subclinical diabetic nerve. Decrease in amplitude of compound sensory action potential of sural nerve is another earlier abnormality, which is, then, accompanied by a fall in motor amplitude of peroneal nerve in advanced patients. Recently, our own group of Hirosaki has demonstrated that somatosensory central conduction time (CCT) between the spinal cord entry time and the arrival time to the sensory cortex is prolonged in diabetics. This abnormality might be partly responsible for the irreversible sensory deficits of diabetic neuropathy.     

神经传导测定技术对腕管综合征病情评估的价值

目的:近年来腕管综合征发病率逐年升高,然而其慢性、隐匿性不易引起人们的重视,发现时往往已造成较大的危害。本文探讨腕管综合征的神经传导测定对病情评估的临床价值,旨在为患者腕管综合征早期发现和后续治疗提供进一步的临床参考依据。方法:选取我院124例确诊的腕管综合征患者。其中无大鱼际肌萎缩者有64例,并选取平均年龄相近的64例正常人作为对照(组A);有大鱼际肌畏缩者60例,并选取平均年龄相近的60例正常人作为对照(组B)。A、B组均经行神经电图检查,握力测定和两点辨别觉测定,分析神经传导速度改变与感觉、运动功能减退程度的关系。结果:A、B两组患者均有不同程度的神经传导改变:在A组患者神经传导改变中,运动和感觉传导速度(MCV和SCV)轻度下降,运动和感觉电位波幅(CMAP和SNAP)轻度下降,潜伏期(ML)轻度延长;在B组患者神经传导中,运动和感觉传导速度(MCV和SCV)明显下降,运动和感觉电位波幅(CMAP和SNAP)明显下降,潜伏期明显延长。结论:腕管综合征患者不同的临床表现有不同程度的神经电图表现,因此神经电图对神经传导的测定结果对腕管综合征患者的病情有良好的评估价值,值得临床推广。     

Evoked potential findings in Behçet's disease. Brain-stem auditory,visual, and somatosensory evoked potentials in 44 patients

We studied 54 patients with Behçet's disease, 41 males and 13 females, mean age 28 years. Forty-four patients had auditory brain-stem evoked potential (BAEP) recordings, 39 had pattern reversal visual evoked potentials (VEP), 27 had median nerve somatosensory evoked potential (SEP) recordings, and 25 tibial nerve SEPs. BAEPs were abnormal in 16 patients (52%) with neurological manifestations and in 4 (31%) without, because of decreased amplitude of wave V, prolonged I–III or III–V interpeak latencies, or uncertain/absent waves III and/or V. Eleven patients (40%) with neurological symptoms and 3 patients (25%) without, had abnormal VEPs. Absent potentials, decreased amplitude, with or without prolonged P100 latency, were found in 75% of the cases, the rest had prolonged P100 latency only. Median SEPs were abnormal in 8 patients (38%) with neurological manifestations. Four patients (21%) had abnormal tibial SEPs. Decreased amplitude with or without mild slowing in central conduction was the predominant SEP abnormality. SEPs were normal in all patients without neurological symptoms. In total, 84% of patients with, and 38% of patients without, neurological symptoms had abnormalities of one or more EP modality.When used cautiously, EP studies in Behçet's disease might be helpful to separate neuro-Behçet from other disorders with similar symptomatology, to disclose subclinical CNS involvement, to evaluate and monitor CNS disease activity, and to provide objective measures of treatment response.     

Functional deficits of central sensory and motor pathways in patients with cervical spinal stenosis: a study of SEPs and EMG responses to non-invasive brain stimulation

The central conduction time of the descending and ascending fibers of the spinal cord were examined in patients with radiologically defined cervical spinal stenosis (antero-posterior diameter of the spinal canal less than 13 mm). Nineteen patients were examined, only 4 of whom showed clinical signs of spastic weakness or ataxia. The electromyographic response after non-invasive stimulation of the leg area of the motor cortex was delayed in13 of the 15 clinically unaffected patients. The central latency (N21-P39) of the somatosensory evoked response after stimulation of the tibial nerve (tibialis SEP) was increased in 12 of the 15 individuals. The 4 patients with clinical signs showed abnormal latencies with both methods.The use of both techniques for the examination of the function of the spinal cord revealed increased latencies in the central motor and/or sensory pathways in all patients. The technique of non-invasive stimulation of the corticospinal system therefore provides an additional tool to detect and quantity subclinical and clinically apparent lesions in patients with defined cervical spinal stenosis.     

Unpleasant visual stimuli increase the excitability of spinal motor neurons

Abstract

Purpose: In physical therapy for post-stroke patients, we often experience cases in which unpleasant emotions cause abnormal muscle tonus. Previously, we suggested that the magnitude of spinal motor neuron excitability was correlated with the grade of muscle tonus. Therefore, spinal motor neuron excitability was considered to be a useful index to evaluate the influence of unpleasant emotions on muscle tonus. In this study, we investigated whether unpleasant emotions evoked by visual stimuli affected the excitability of spinal motor neurons.

Materials and Methods: The F-waves, an indicator of spinal motor neuron excitability, were measured in 19 healthy adult volunteers. Firstly, for the rest trial, F-waves were measured during relaxation to determine the baseline of spinal motor neuron excitability. Following the rest trial, the unpleasant trial was conducted in which F-waves were measured while the subjects viewed an unpleasant picture for 1?min. After the unpleasant trial, F-waves were measured during relaxation. For the control condition, F-waves were measured while the subjects viewed a neutral picture instead of the unpleasant picture. The recorded F-wave data were analysed for persistence and the F/M amplitude ratio.

Results: Persistence and the F/M amplitude ratio were significantly greater during the unpleasant trial than during the rest trial. In the control condition, there was no significant difference in persistence and the F/M amplitude ratio compared with the three trials.

Conclusions: Our findings indicate that unpleasant emotions may affect spinal motor neuron excitability. Therefore, learning how to control emotions should be important aspect of physical therapy.     

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.     

Neurophysiological Differences between Flail Arm Syndrome and Amyotrophic Lateral Sclerosis

There are many clinical features of flail arm syndrome (FAS) that are different from amyotrophic lateral sclerosis (ALS), suggesting they are probably different entities. Studies on electrophysiological differences between them are limited at present, and still inconclusive. Therefore, we aimed to find clinical and neurophysiological differences between FAS and ALS. Eighteen healthy control subjects, six FAS patients and forty-one ALS patients were recruited. The upper motor neuron signs (UMNS), split-hand index (SI), resting motor threshold (RMT), central motor conduction time (CMCT) were evaluated and compared. There was no obvious upper motor neuron signs in FAS. The SI and RMT level in FAS was similar to control subjects, but significantly lower than that of in ALS. Compared with control group, the RMT and SI in ALS group were both significantly increased to higher level. However, no significant difference of CMCT was found between any two of these three groups. The differences in clinical and neurophysiological findings between FAS and ALS, argue against they are the same disease entity. Since there was no obvious UMNS, no split-hand phenomenon, and no obvious changes of RMT and CMCT in FAS patients, the development of FAS might be probably not originated from motor cortex.     

Neurophysiological evaluation of central-peripheral sensory and motor pudendal fibres

Extensive neurophysiological investigations were carried out in 18 healthy volunteer subjects, and 6 patients with neurological disease. The tests consisted of spinal and scalp somatosensory evoked potentials (SEPs) to stimulation of the dorsal nerve of penis/clitoris, motor evoked potentials (MEPs) from the bulbocavernosus muscle (BC) and anal sphincter (AS) in response to scalp and sacral root stimulation, and measurement of sacral reflex latency (SRL) from BC and AS.In the control subjects, the mean sensory total conduction time (sensory TCT), as measured at the peak of the scalp P40 wave was 40.9 msec (range: 37.8–44.2). The mean sensory central conduction time (sensory CCT = spine-to-scalp conduction time) was 27.0 msec (range: 23.5–30.4).Transcranial brain stimulation was performed by using a magnetic stimulator both at rest and during voluntary contraction of the examined muscle. Sacral root stimulation was performed at rest. Motor total conduction times (motor TCT) to BC and AS muscles were respectively 28.8 and 30.0 msec at rest, and 22.5 and 22.8 msec during contraction. Motor central conduction times (motor CCT) to sacral cord segments controlling BC and AS muscles were respectively 22.4 and 21.2 msec at rest, and 15.1 and 12.4 msec during contraction.The mean latencies of SRL were respectively 31.4 msec in the bulbocavernosus muscle and 35.9 msec in the anal sphincter. Combined or isolated abnormalities of SEPs, MEPs and SRL were found in a small group of patients with neurological disorders primarily or secondarily affecting the genito-urinary tract.     

Somatosensory evoked potentials and magnetic resonance imaging in syringomyelia

Somatosensory evoked potentials (SEPs) to median and posterior tibial stimulation were obtained in 22 patients with syringomyelia. All patients had magnetic resonance imaging (MR) which defined the maximum transverse diameter of the syrinx as well as its longitudinal extension. SEP was abnormal in 16 (72%) patients. Median and posterior tibial SEPs were abnormal in 11 and 15 patients respectively. Both tests were abnormal in 10 patients. Ten patients showed absence of one or more central potentials (P/N13, N20, N22) and 7 patients demonstrated increased conduction times (N9–N20, P/N13–N20, N22–P40). The mean maximum transverse diameter of the syrinx was 7.5 mm in patients with normal SEPs and 16.2 mm in patients with abnormal SEPs. Abnormal SEP was observed in all 5 patients with loss of position sense, in 9 of 13 (69%) with loss of superficial pain and temperature, and 1 of 2 patients with motor deficit only. Central SEP abnormalities were observed in 3 of 5 patients with sensory deficits indistinguishable from a peripheral neuropathy and in 2 patients in the asymptomatic extremity. Three of 4 patients with syringomyelia and Chiari malformation had a normal SEP.     

Electrocardiographic abnormalities in patients with myotonic dystrophy.

In examining the incidence and progression of electrocardiographic abnormalities in 45 patients with myotonic dystrophy, 26 (58%) of whom at entry had at least 1 electrocardiographic abnormality, we found conduction abnormalities in 17 (38%). In 21 patients (47%), new abnormalities developed during follow-up (mean, 4.6 years). The overall incidence of electrocardiographic abnormalities increased to 78%, and the incidence of conduction defects increased to 62%. Second-degree or complete atrioventricular block did not develop in any of the patients. Pseudoinfarction patterns were common at entry and during follow-up and were not correlated with evidence of clinical coronary artery disease. There was no correlation between the presence of electrocardiographic abnormalities and apparent disease severity.     

Latency and amplitude abnormalities of the scalp far-field P14 to median nerve stimulation in multiple sclerosis. A SEP study of 122 patients recorded with a non-cephalic reference montage

The frequency and characteristics of P14 abnormalities were investigated in 122 patients with probable (68), or definite (54) multiple sclerosis by recording SEPs to median nerve stimulation with a non-cephalic reference montage. The most frequent SEP abnormality found in our series (62% of abnormal results) combined latency increase and amplitude reduction of P14. Interindividual variability, inherent in absolute amplitude measurements, was by-passed by calculating the ration between the amplitudes of far-field P9 and P14 components, which proved to be normally distributed in controls. In spite of the strong association (P ⪡ 0.001) between the P9–P14 interpeak interval (IPL) and the P9/P14 amplitude ratio in MS patients, the latter parameter was found to be the only abnormality in 12 patients whose P9–P14 and P14–N20 IPLs were normal. Also IPLs were increased in 12 patients with normal P14 amplitudes. These results suggest that adding the P9/P14 amplitude criterion to standard IPL data might be useful to detect conduction troubles in MS patients.     

Altered patterns of muscle activation during performance of four functional tasks in patients with shoulder disorders: interpretation from voluntary response index.

Altered motor control of the shoulder muscles during performance of a specific motor task in patients with shoulder disorders (SDs) has been an interesting subject to researchers. This study compared shoulder muscle activation patterns by surface electromyography (sEMG), including the upper trapezius (UT), lower trapezius (LT), and serratus anterior (SA) muscles, during four functional tasks in 25 patients with SDs and controls. A voluntary response index (VRI) was calculated, including magnitude and similarity index (SI), to quantify sEMG patterns during four functional tasks. Responsiveness and clinically meaningful levels of discrimination between patients and control for EMG magnitude and SI were determined. An altered pattern of motor control during four functional tasks was evident in the patients, in which greater EMG amplitude and abnormal EMG patterns were found. For SI among four functional tasks, normal subjects ranged from 0.80 to 1.00 while patients ranged from 0.70 to 0.99. High probabilities (97%) of discrimination between patients and normal subjects were found by SI method during an overhead height task (patients: 0.85-0.96, normal subjects: 0.95-1.00). Our results also suggest that an individual can be estimated to be abnormal when lower SI values are observed during the four functional tasks.     

Mononeuropathies of the radial nerve: clinical and neurographic findings in 91 consecutive cases.

Retrospective features of 91 consecutive cases (68 men, 23 women; mean age 44.4 years) of radial mononeuropathy diagnosed over the last 8 years in two electromyography (EMG) services are reported to define the clinical and electrophysiological findings of radial neuropathies in relation to traumatic and non-traumatic causes and site of injury. The occurrence of radial neuropathy was 0.65 x 100 first electromyographic examinations. The most frequent site of damage was the main trunk at the spiral groove of the humerus (36%); the most frequent cause was nerve trauma (70%) due to fracture (36%). In neuropathies of the main trunk and posterior interosseous (PI) nerve, "complete nerve injury" was observed in 36% of cases, conduction motor block in 33% and motor conduction velocity slowing in 46%. At least one of these findings was present in 51%, whereas motor neurography was normal in 13% of cases. Sensory action potential (SAP) anomalies were observed in 51% of cases. In neuropathy of the superficial radial nerve, no SAP was detected in 30% of cases; in all others except one, SAP was reduced in amplitude. Non-traumatic neuropathies showed severer conduction block and less severe anomalies of SAP than traumatic neuropathies. No differences were found between men and women. EMG is essential for confirming the site of injury and neurographic study may be helpful for diagnosis, providing information about lesion type and severity.     

The diabetic polyneuropathy. I. Relation between impaired function in peripheral nerves and clinical findings

789 patients with diabetes mellitus were studied by clinical and electroneurographical investigation. Motor and sensory conduction velocities of the median nerve and motor conduction velocity of the tibial nerve were determined. 86.1% of the patients suffered from juvenile diabetes, and 13.9% from maturity onset diabetes. Average duration of the disease was 9.5 years, average age of the patients was 26.7 years. Clinical signs of polyneuropathy were found in 19.1%. In 40.9% of the patients at least one of 3 conduction velocities was found to be delayed. Patients with clinical signs of polyneuropathy exhibited delayed nerve conduction velocities and delayed distal latencies. Diagnosis of polyneuropathy almost with certainty is possible by determining the three nerve conduction velocities and the three corresponding distal latencies. 22% of patients without clinical signs of polyneuropathy exhibited electroneurographical signs of impaired peripheral nerve function. Heredity, body weight, lipid metabolism, actual metabolic balance, and treatment were found to be without any significant influence on nerve conduction velocity.     

Neurophysiological study to assess the severity of each site through the motor neuron fiber in entrapment neuropathy

The purpose of this study is to evaluate prospectively the sensitivities of conventional and new electrophysiological techniques and to investigate their relationship with the body mass index (BMI) in a population of patients suspected of having carpal tunnel syndrome (CTS). In this study, 165 hands of 92 consecutive patients (81 female, 11 male) with clinical diagnosis of CTS were compared to reference population of 60 hands of 30 healthy subjects (26 female and 4 male). Extensive sensory and motor nerve conduction studies (NCSs) were performed in the diagnosis of subtle CTS patients. Also, the patients were divided into subgroups and sensitivities were determined according to BMI. The mean BMI was found to be significantly higher in the CTS than in the control group (p < 0.001). The sensitivity of the median sensory nerve latency (mSDL) and median motor distal latency (mMDL) were 75.8% and 68.5%, respectively. The most sensitive parameters of sensory and motor NCSs were the difference between median and ulnar sensory distal latencies to the fourth digit [(D4M-D4U), (77%)] and the median motor terminal latency index [(mTLI), (70.3%)], while the median-to-ulnar sensory action potential amplitude ratio (27%) and the median-thenar to ulnar-hypothenar motor action potential amplitude ratio (15%) were least sensitive tests. Sensory tests were more sensitive than motor NCSs. Combining mSDL with D4M-D4U, and mMDL with mTLI allowed for the detection of abnormalities in 150 (91%) and 132 (80%) hands, respectively. Measurements of all NCSs parameters were abnormal in obese than in non-obese patients when compared to the BMI. The newer nerve conduction techniques and combining different NCSs tests are more sensitive than single conventional NCS test for the diagnosis of suspected CTS. Meanwhile, CTS is associated with increasing BMI.     

肌电图检查评估腕管综合征手术效果的临床分析

目的:探讨采用肌电图检查评估腕管综合征的手术治疗效果。方法:选取35例(患侧手共39侧)临床确诊为腕管综合征并接受腕管切开减压术治疗的患者,于手术前后分别行肌电图检查,应用正中神经传导检查和拇短展肌针极肌电图检查,分析患者手术前和手术后腕部正中神经功能的变化情况。结果:手术后,患者正中神经感觉传导潜伏期异常率(33%)、正中神经运动传导潜伏期异常率(36%)较手术前(72%、74%)明显下降(P0.05),正中神经感觉传导波幅(7.40±5.05)较手术前(4.86±3.60)显著降低(P0.001),拇短展肌静息状态下失神经电位的异常率(69%)、重收缩时募集电位异常率(13%)均较手术前(85%、26%)明显下降(P0.05)。患者手术前后正中神经感觉传导速度和运动传导速度对比差异无统计学意义(P0.05)。结论:腕管切开减压术可解除正中神经卡压状态,明显恢复正中神经功能,增强拇短展肌肌力,临床治疗效果好。肌电图检查可为腕管综合征患者手术治疗效果的评估提供客观的依据。     

Magnetic stimulation of the corticospinal tracts in Pelizaeus-Merzbacher disease

To evaluate conduction abnormalities of the corticospinal tracts (CSTs) in Pelizaeus-Merzbacher disease (PMD), magnetic stimulation at three levels was carried out in 3 boys with PMD aged between 9 and 12 years. They were all diagnosed as having a duplicated proteolipid protein gene. The motor cortex and cervical spinal roots were stimulated with a round coil, whereas a double cone coil was used for brain-stem stimulation. Surface electromyographic (EMG) recording was performed on the first dorsal interosseous muscles. Despite a normal EMG response to cervical stimulation, magnetic shock of the motor cortex elicited no EMG activity, even in the case with less motor symptoms. This discrepancy between the electrophysiological and clinical findings is likely due to slowing conduction, which reduces the temporal summation of multiple descending volleys magnetically elicited. A partial conduction block may also occur because of the lack of an EMG response to brain-stem stimulation. Thus, we speculated that the spastic paresis in PMD is associated with both slowing conduction and a partial conduction block in the CSTs.     

The assessment of severe head injury by short-latency somatosensory and brain-stem auditory evoked potentials

The relative prognostic value of short-latency somatosensory evoked potentials (SEPs) and brain-stem auditory evoked potentials (BAEPs) was assessed in 35 patients with post-traumatic coma. Analysis of the evoked potentials was restricted to those recorded within the first 4 days following head injury. Abnormal SEPs were defined as an increase in central somatosensory conduction time or an absence of the initial cortical potential following stimulation of either median nerve. Abnormal BAEPs were classified as an increase in the wave I–V interval or the loss of any or all of its 3 most stable components (waves I, III and V) following stimulation of either ear. SEPs reliably both good and bad outcomes. All 17 patients in whom SEPs were graded as normal had a favourable outcome and 15 of 18 patients in whom SEPs were abnormal had an unfavourable outcome. Although abnormal BAEPs were associated with an unfavourable outcome in almost all patients (6 of 7), only 19 of 28 patients with normal BAEPs had a favourable outcome. The finding of normal BAEPs was therefore of little prognostic significance. These results confirm the superiority and greater sensitivity of the SEP in detecting abnormalities of brain function shortly after severe head trauma.     

Abnormalities of parietal and prerolandic somatosensory evoked potentials in Huntington's disease

Cervical, parietal and prerolandic somatosensory evoked potentials (SEPs) to median nerve stimulation at the wrist were recorded with an earlobe reference in 24 patients with Huntington's disease (HD) and in 24 age-matched normal controls. Cortical responses of abnormal wave form and reduced amplitude were constantly observed in HD patients. SEP changes affected more severely the prerolandic (P22/N30) pattern, which could not be recognized in two-thirds of patients, than the parietal (N20/P27) pattern, which could be identified in all cases. The N20 latency and the central conduction time (N13–N20 interval) were significantly increased. The occurrence of abnormalities of central conduction and of a predominant involvement of the prerolandic SEP pattern suggests an impairment of impulse transmission along the somatosensory lemniscal pathway at subcortical, possibly thalamic, level in HD.