Conduction of the palmar cutaneous branch of the median nerve

The palmar cutaneous branch of the median nerve (PCBMN) usually arises about 5.5cm proximal to the radial styloid and innervates skin of the thenar eminence. The nerve may be injured by direct trauma or during surgery at the wrist. The action potential of the nerve was recorded in 50 nerves of 25 normal subjects, by antidromic stimulation of the median nerve 10cm from the surface recording electrode over the midthenar eminence. The mean latency and mean amplitude of the evoked response were 2.6 +/- 0.2msec and 12 +/- 4.6 mu v, respectively. The mean duration of the evoked potential was 1.78msec. The technique is simple and may be useful in evaluating lesions of the PCBMN.     

Ulnar palmar cutaneous nerve and hypothenar sensory conduction studies.

The ulnar palmar cutaneous nerve (UPCN) is potentially useful to the electrodiagnostician. However, no definitive nerve conduction study techniques for the UPCN have been reported. The UPCN supplies sensory innervation to the hypothenar palm. This study describes an orthodromic sensory conduction technique for the hypothenar palm. Data were collected from 20 normal limbed patients (ages 22-58). Potentials were recorded over the ulnar nerve 10cm proximally and at the elbow. Distal latency was 2.19 +/- 0.17msec, and distal amplitude was 12.7 +/- 6.9uv. Additionally, a modified collision technique was used in several subjects to examine the possibility of volume conduction to more than one ulnar nerve branch. The techniques described may be useful in selected cases of distal ulnar nerve pathology. A case is reported in which injury to the superficial sensory branch of the ulnar nerve, with sparing of the UPCN was demonstrated electrodiagnostically. Further study is needed to determine if the UPCN can consistently be electrophysiologically isolated.     

Median "pseudoneurapraxia" at the wrist: reassessment of palmar stimulation of the recurrent median nerve

OBJECTIVE: To determine the occurrence and effect of incidental deep ulnar nerve (DUN) costimulation during palmar stimulation of the recurrent median nerve (RMN). DESIGN: Observational. SETTING: Electromyography laboratory. PARTICIPANTS: Seventeen asymptomatic adult volunteers (34 hands) and 4 fresh cadaver hands. MAIN OUTCOME MEASURES: Median nerve stimulation at the wrist and careful incremental surface and subcutaneous (needle) palmar stimulation were performed while recording thenar and first dorsal interosseous manus compound muscle action potentials. Thenar palm-to-wrist amplitude difference (P -- W Delta) and palm-to-wrist amplitude ratio (P/W) were compared with published values. Correlation of DUN costimulation with falsely elevated P -- W Delta and P/W values was assessed. Multiplanar magnetic resonance imaging (MRI) and subsequent dissection of 4 fresh cadaver hands was done to measure the distance between the RMN and DUN at the palmar stimulation site. RESULTS: Two groups emerged: Group I (63%), with DUN stimulation, and II (37%), with no DUN stimulation. When DUN costimulation occurred (Group I), there was a statistically significant increase in P -- W Delta (p =.002 percutaneous, p =.02 subcutaneous) and P/W (p =.004 percutaneous, p =.007 subcutaneous) when compared with previously published data. Combining all trials on all hands, 53% and 25% had P -- W Delta values and P/W values that exceeded previously published normative data, respectively. The mean distance between the DUN and RMN at the palmar stimulation site was determined by dissection (1.2cm) and MRI (1.5cm). CONCLUSIONS: Close proximity of the DUN to the RMN causes frequent and often unavoidable DUN activation during palmar stimulation of the RMN. This inadvertent stimulation may cause a false diagnosis of median neurapraxia at the wrist.     

Conduction studies of the medial cutaneous nerve of the forearm

The forearm medial cutaneous nerve is a pure sensory branch from the medial cord of the brachial plexus. Its fibers are derived from the eighth cervical and first thoracic nerves. A simple, easily reproducible antidromic technique for studying conduction of the forearm medial cutaneous nerve is described with the knowledge (obtained from cadaver dissections) of its exact topography. Sixty nerves were studied in 30 able-bodied adults, 15 women and 15 men. Surface stimulation was done over the medial aspect of the middle of the arm at a level where the nerve pierces the deep fascia. Surface recordings were made 18cm distally over the course of its volar branch. Action potentials were obtained in 100% of the subjects without electronic averaging. Mean values obtained were as follows: latency to onset 2.73 +/- 0.17 msec; latency to peak 3.31 +/- 0.19 msec; conduction velocity of the fastest fibers 65.9 +/- 4.3 m/s; amplitude 15.4 +/- 4.1 microvolts, and the mean difference in latency between the right and left nerves in the same subject was 0.1 msec. Conduction studies of this nerve should be useful in electrodiagnostic evaluation of peripheral neuropathy (particularly in below amputees), local neuropathic conditions, and entrapment syndromes involving the medial cord of the brachial plexus.     

Sensitivity of median sensory nerve conduction tests in digital branches for the diagnosis of carpal tunnel syndrome

OBJECTIVE: To compare the sensitivity of median sensory nerve conduction tests performed by stimulating digital branches in patients with carpal tunnel syndrome. DESIGN: A prospective study in 506 hands of patients with carpal tunnel syndrome diagnosed electrophysiologically. RESULTS: The sensitivity of median sensory nerve conduction tests across the first three digit-to-wrist segments and palm-to-wrist segment was determined. The most common abnormal electrophysiologic finding was the slowing of sensory nerve conduction velocity over the palm-to-wrist segment, which was detected in 98.5% of the hands. Slowing of sensory nerve conduction velocity over the digit 1-, 2-, and 3-to-wrist segments of the median nerve was found in 95.4%, 88%, and 82% of the hands, respectively. CONCLUSION: The sensory nerve conduction velocity test of the digit 1-to-wrist segment has the most sensitivity among the three digital branches of the median sensory nerve, and it may be used more widely in the electrodiagnosis of carpal tunnel syndrome.     

Left-hemisphere-dominant SII activation after bilateral median nerve stimulation

We used bilateral median nerve stimuli to find out possible hemispheric dominance in the activation of the second somatosensory cortex, SII. Somatosensory evoked fields (SEFs) were recorded from 14 healthy adults (7 right-handed, 7 left-handed) with a 306-channel neuromagnetometer. Electrical stimuli were applied once every 3 s simultaneously either to the left and right median nerves at the wrists or to the palmar skin of both thumbs. Sources of SEFs were modeled with four current dipoles, located in the SI and SII cortices of both hemispheres. The SI activation strengths did not differ between the hemispheres, whereas the SII responses were significantly stronger in the left than in the right hemisphere. In right-handers, the left/right SII ratios were 1.9 and 1.8 for wrist and thumb stimuli, respectively. The corresponding values were 1.5 and 1.7 in left-handers. The results indicate handedness-independent functional specialization of the human SII cortices.     

带血供溃变神经游离移植后肌电图及组织学变化

目的:从神经血供和溃变两方面对自体神经的移植效果进行分析,观察神经游离移植后的电生理及组织学变化。方法:实验于2001-01/2002-06在白求恩国际和平医院动物实验室完成。①实验分组及方法:选用Wistar大鼠120只,按随机数字表法分为7组,正常对照组12只;其余108只根据移植神经的溃变时间分为3组,分别为健康(未溃变)、溃变1,4周组,每组再根据是否存在尺神经血供分为带和不带血供神经移植组。以双上肢为观察对象,以尺神经桥接正中神经缺损。②实验评估:各组分别于术后第4,8,12周在移植尺神经的中段和正中神经远端距吻合口3mm处,分别取材进行显微解剖观察和光镜观察,测量移植尺神经及正中神经远端横截面轴突的数目,并计算出有髓神经轴突的再生率;于术后第12周测定神经传导速度、诱发电位波幅及潜伏期;术后第12周切取正中神经行电镜观察。结果:120只大鼠全部进入结果分析。①神经外观各组间无明显差异,健康神经移植组移植术后神经与周围组织间粘连最轻。②移植术后第8,12周,相同溃变时间带血供组的神经轴突再生率高于不带血供组(P<0.05);健康神经组高于溃变神经组(P<0.05)。健康神经组与溃变1周组神经纤维生长情况差异无显著性意义(P>0.05)。③移植术后12周,相同溃变时间带血供组的尺神经及正中神经传导速度、诱发电位波幅均高于不带血供组(P<0.05),潜伏期短于不带血供组(P<0.05),而带血供组组间以及不带血供组差异均无显著性意义(P>0.05)。④带血供溃变1周神经轴突生长最好。结论:带血供溃变神经移植优于不带血供的溃变神经,带血供的短期溃变神经可以用来代替健康神经移植。     

Thumb force deficit after lower median nerve block

PURPOSE: The purpose of this study was to characterize thumb motor dysfunction resulting from simulated lower median nerve lesions at the wrist. METHODS: Bupivacaine hydrochloride was injected into the carpal tunnel of six healthy subjects to locally anesthetize the median nerve. Motor function was subsequently evaluated by measuring maximal force production in all directions within the transverse plane perpendicular to the longitudinal axis of the thumb. Force envelopes were constructed using these measured multidirectional forces. RESULTS: Blockage of the median nerve resulted in decreased force magnitudes and thus smaller force envelopes. The average force decrease around the force envelope was 27.9%. A maximum decrease of 42.4% occurred in a direction combining abduction and slight flexion, while a minimum decrease of 10.5% occurred in a direction combining adduction and slight flexion. Relative decreases in adduction, extension, abduction, and flexion were 17.3%, 21.2%, 41.2% and 33.5%, respectively. Areas enclosed by pre- and post-block force envelopes were 20628 +/- 7747 N.N, and 10700 +/- 4474 N.N, respectively, representing an average decrease of 48.1%. Relative decreases in the adduction, extension, abduction, and flexion quadrant areas were 31.5%, 42.3%, 60.9%, and 52.3%, respectively. CONCLUSION: Lower median nerve lesion, simulated by a nerve block at the wrist, compromise normal motor function of the thumb. A median nerve block results in force deficits in all directions, with the most severe impairment in abduction and flexion. From our results, such a means of motor function assessment can potentially be applied to functionally evaluate peripheral neuropathies.     

正中神经前臂分支与旋前圆肌的关系以及旋前圆肌肌内神经分布研究

目的:为正中神经与旋前圆肌的临床应用提供形态学基础.方法:解剖观察30具成人尸体的正中神经前臂分支,并用Sihler′s肌内神经染色法对5具成人尸体的旋前圆肌进行染色,观察其肌内神经分支分布.结果:(1)正中神经前臂分支密集区最远一个束支距离肱骨内上髁(7.63 ± 1.15)cm,该距离占前臂长的29%.旋前圆肌长(14.01 ± 0.91)cm.旋前圆肌止点中点距离肱骨外上髁(13.31 ± 0.81)cm,该距离占前臂长的52%.(2)正中神经从其两侧各分出1支一级分支从旋前圆肌外上方进入该肌,其中尺侧支分布到旋前圆肌肱骨头近侧半,桡侧支分布到旋前圆肌肱骨头远侧半及其尺骨头.结论:正中神经前臂肌支有近端集中、偏向尺侧以及与旋前圆肌位置关系密切的分布特点,这些分布特点对前臂创伤修复有一定的参考意义.旋前圆肌有来自正中神经的较恒定的分支分布,该肌可分为肱骨头亚部与尺骨头亚部,供肌亚部移植.     

Electrophysiologic study of the anterior interosseous nerve

Nerve conduction studies of the anterior interosseous nerve were performed on 26 healthy subjects (6 women and 20 men, aged 24 to 63 years). The compound muscle action potential from the pronator quadratus muscle was obtained by using surface electrodes placed over the dorsal aspect of the distal forearm and median nerve stimulation at the elbow. The latency of the evoked potential was determined over distances that ranged from 17.5-28 cm from the elbow to the pronator quadratus muscle; this resulted in latencies of 3.5 ms (+/- 0.4) and 3.6 ms (+/- 0.4) for the left and right extremities, respectively, with a side-to-side difference of 0.1 ms (+/- 0.1). The amplitude of the potentials recorded was 3.1 mV (+/- 0.8); a difference in amplitude of 11.4% (+/- 7.7%) between extremities was seen. Although duration measurements were obtained, the frequent presence of biomodal peaks made interpretation difficult. This bimodal pattern was felt to represent either two heads of the pronator quadratus or another muscle innervated by the anterior interosseous nerve. The technique in the present study is easy to perform, allows better assessment of the compound muscle action potentials obtained and provides for side-to-side comparisons of latency and amplitude. This technique aids the electromyographer in evaluation of suspected cases of injury to the anterior interosseous nerve, particularly in unilateral cases.     

正中神经损伤后手部感觉功能的康复训练

目的 观察正中神经损伤后早期康复训练对手部感觉功能恢复的影响。方法 将70例正中神经损伤患者随机分为康复组及对照组，康复组于术后2周开始康复治疗，并在康复治疗前及治疗过程中，参照国际标准分别评定手的感觉等级及两点辨别觉，对照组仅行一般处理。经过1个疗程(6—8周)治疗后，进行第2次评定，以后每1个疗程评定1次，共4-5次。结果 康复组患者手的感觉功能优良率达88％，有效率达97％。结论 感觉康复训练能够促进正中神经损伤患者手的感觉功能恢复。     

Electrophysiologic investigation of mandibular nerve injury

Isolated lesions of the mandibular branch of the trigeminal nerve have only rarely been reported. We report the occurrence of an isolated lesion of the mandibular nerve associated with a unilateral mandibular fracture, and its substantiation electrophysiologically. A 65-year-old man was involved in a motor vehicle accident resulting in multiple fractures, including a unilateral mandibular fracture and temporomandibular joint dislocation. No evidence of intracranial pathology by CT scan was noted and the neurologic examination was nonfocal except for dysfunction of the mandibular nerve ipsilateral to the fracture site. Bilateral facial nerve latency and blink reflexes were normal. EMG evaluation of the muscles of facial expression and mastication demonstrated denervation confined to the muscles innervated by the mandibular branch of the trigeminal nerve. In patients complaining of facial sensory dysfunction, malocclusion, or weakness of muscles of mastication after mandibular fracture, an electrophysiologic examination can assist in evaluating cranial nerve integrity.     

Dorsal ulnar cutaneous nerve conduction studies in an asymptomatic population

OBJECTIVES: To establish the average distal sensory latency and amplitude of the dorsal ulnar cutaneous nerve under controlled temperature and settings. DESIGN: Dorsal ulnar cutaneous nerve conduction studies were performed with a bar electrode between the fourth and fifth metacarpals. The nerve was stimulated at 8 and 10cm from the active electrode. The temperature of the limbs under study was kept at 32 degrees C to 35 degrees C. PARTICIPANTS: Fifty-four arms of 27 subjects were studied. RESULTS: Results showed that distal sensory latencies were normally distributed. The average distal sensory latencies at 8cm and 10cm were 1.84 +/- .20msec and 2.09 +/- .21msec, respectively, with average amplitudes of 26.5 +/- 9.7microV and 23.5 +/- 8.8microV. Comparison with a previously reported study in which the limb temperature was not controlled showed a statistically significant difference. CONCLUSION: It is important to use standardized technique and to measure and maintain optimal temperature of the arm under study to prevent erroneous results and misdiagnosis.     

Electrophysiologic responses of human sural nerve to temperature

The purpose of this study was to assess the conduction, specifically the latency and amplitude of the sensory nerve action potential (SNAP), of the sural nerve as a function of intraneural temperature of the leg. The electrophysiologic responses of the sural nerve were determined at different temperatures in 22 healthy adults. Distal sensory latency and amplitude of the sural SNAP was determined at 1 degree C intervals over a limb temperature range of 23 degrees to 40 degrees C. Limb temperature was monitored with a thermistor probe placed subcutaneously near the sural nerve. Ice bath soaks were used for cooling and infrared radiation for warming the limbs. An analysis of covariance was performed for the SNAP latencies and amplitudes to determine the effect of gender and leg (right or left) at each temperature level. No effect of gender or leg on neural conduction was detected in individual subjects. A regression analysis was then used on pooled data to determine the effect of temperature on sural SNAP latency and amplitude. An inverse linear change in the latency of sural SNAP was observed over the temperature ranges used. Mean latency increased 0.1 msec per 1 degree C increase in subcutaneous temperature. A direct relationship between amplitude of the SNAP and temperature was determined. Mean amplitude increased 0.3 muV per 1 degree C increase in subcutaneous temperature. The results of this study support previous reports, which state that SNAP latency is indirectly related to the intraneural temperature. Clinical electromyographers must monitor the temperature of the lower leg and foot whenever sensorineural conduction of the lower limbs is performed.     

大鼠颈神经前支受压后电生理及解剖学改变

目的观察大鼠颈神经前支受压后的电镜及电生理改变,设计大鼠颈神经前支受压模型。方法Wistar雄性大鼠,用直径1 mm硅胶管,纵形切开,于接近背根神经节远端套入颈6神经前支,以丝线在硅胶管外轻松结扎。结扎前、术后2周及4周测定肌皮神经躯体诱发电位,并于2周、4周取受压部位神经段、对侧正常神经及双侧背根神经节作电镜检查。结果受压2周及4周后肌皮神经躯体诱发电位波幅低于结扎前,潜伏期比结扎前延长,差异有统计学意义。受压段神经呈纤维变性、神经脱髓鞘及炎症改变。结论本模型具有切实可行、经济、方便的特点,可作为颈神经受压进一步研究的实验模型。     

正中神经或尺神经损伤后手掌不同部位交感神经皮肤反应研究

目的研究正中神经和尺神经绝对支配区交感神经皮肤反应（SSR）的特征及其临床意义。 方法以健康志愿者30人（正常组）、正中神经损伤患者10例（正中神经损伤组）、尺神经损伤患者10例（尺神经损伤组）以及正中神经、尺神经均损伤患者3例（正中神经尺神经损伤组）为研究对象,采用神经肌电图电刺激方法引出SSR,分别在掌心、小鱼际、示指和小指指腹记录潜伏期和波幅,并进行统计学分析。 结果正中神经完全损伤后,示指指腹SSR消失,掌心SSR波幅降低,而小指指腹SSR正常;尺神经损伤后,小指指腹SSR消失,小鱼际SSR波幅降低,而示指指腹SSR正常。正中神经和尺神经均损伤后,整个掌面均不能引出SSR。 结论掌心和小鱼际SSR受正中神经和尺神经双重影响;示指指腹和小指指腹SSR分别受正中神经和尺神经单一神经通路上的交感神经调控;示指指腹和小指指腹是检测单神经通路上交感传出功能的理想部位。     

In-continuity neuroma of the median nerve at the elbow

Neuromas are a hyperplastic disorganised proliferation of cells that represent an attempt at nerve regeneration after trauma. They can be classified into terminal and in-continuity neuromas; the latter are observed when the nerve stumps are both connected. We present here the case of a 46-year-old male who sustained a deep cut at the volar aspect of the right elbow while repairing a glass. The injury caused partial transection of the median nerve, which was initially unrecognised. After several months, the patient presented pain at the volar aspect of the elbow, worsening with manual compression at the site of previous injury. Ultrasound showed an in-continuity neuroma with a hypoechoic and enlarged median nerve at the site of the sutured wound. The case report shows that ultrasound may be helpful in confirming the clinical diagnosis of neuroma and that it is useful to evaluate the percentage of the area affected by the lesion.