Changes in ulnar nerve conduction velocity across the elbow in different angles of elbow flexion

OBJECTIVES: The goal of this study is to determine the changes in motor and sensory nerve conduction velocity (NCV) of ulnar nerve at elbow area in different angles of elbow flexion and also to define the optimum angle at which there is an ideal correlation between the across elbow and below elbow NCVs of ulnar nerve. METHODS: Motor and sensory NCVs of ulnar nerve were studied in 50 able-bodied subjects (100 limbs) for the below elbow and across elbow segments to evaluate the effect of 5 different angles of elbow (0 degrees, 45 degrees, 90 degrees, 110 degrees 135 degrees of elbow flexion) on NCV changes of ulnar nerve. At each angle the across elbow NCVs were measured and compared with below elbow segments. RESULTS: At 0 degrees of elbow flexion the across elbow NCVs were found to be slower than below elbow segments and at 45 degrees there was no statistical difference between below elbow and across elbow NCV. At each subsequent angles of elbow flexion there was an increment in motor and sensory NCVs for the across elbow compared to below elbow segment (P < 0.05). This increment progressed as the degree of flexion increased, so the most erroneous increment was found at 135 degrees of elbow flexion. CONCLUSIONS: Since the 45 degrees of elbow flexion was found to be the position of least variation in motor and sensory NCVs between the across elbow and below elbow segments, this position of elbow flexion seems to be the ideal angle during nerve conduction study of ulnar nerve at elbow area. In this position the upper limit of normal difference between across elbow and below elbow motor NCVs (mean + 2SD) was calculated 8 m/sec.     

应用MEP，NCV联合诊断糖尿病性神经病

目的：探讨运动诱发电位（MEP）、神经传导速度（NCV）检测对糖尿病（DM）运动神经中枢及神经根、周围神经病变的诊断价值。方法：检测50例DM病人的MEP及NCV。结果：MEP异常率82％（41／50）。表现皮层、脊髓刺激MEP潜伏期延迟、波形分化欠佳,部分伴有中枢运动传导时间（CMCT）异常。MEP异常率与病程长短呈正相关;空腹血糖地MEP结果无明显影响。NCV异常率70％,主要表现运动神经传导速度（MCV）、感觉神经传导速度（SCV）减慢。结论：MEP、NC检查对诊断DM的锥体束功能损害及神经根、周围神经病变有重要价值,二者结合可对DM的神经系统功能提供全面客观指标。     

Unobtainable radial nerve F-waves in a case of radial nerve conduction block

We present here the first known case of an unobtainable radial nerve F-wave in a case of radial nerve conduction block. This case further demonstrates that F-waves are used not only to rule out neuropathy or radiculopathy, but also to detect conduction block.     

Reduced sensory nerve conduction velocity of the distal part of the radial nerve among patients with vibration syndrome

The present study was aimed at clarifying the effects of vibration syndrome (VS) on the distal part of the radial nerve, which is rarely affected by chronic entrapment. Thirty-one patients with VS due to previous exposure to vibration and 18 age-matched controls were examined for sensory nerve conduction velocities in the distal part of the radial nerve (SCV-DR) in the dorsal side of the hand. The patient group was divided into two subgroups, one of those with vibration-induced white finger (VWF) in the thumb or index finger where sensory nerves are innervated by the radial nerve (N = 21) and the other without VWF (N = 10). SCV-DR among the patients was significantly slower than in the controls (t = 3.55, p = 0.00138). The ANOVA of SCV-DR for the three groups showed F2, 46 = 5.25 (p = 0.0088). A significant difference was found between the controls and the VWF (+) group (p = 0.0233), but not between the controls and the VWF (-) group (p = 0.478) by multiple comparison using Scheffe's method. These findings suggest that VS affects the radial nerve with a direct vibration effect and/or a co-operative effect with direct circulatory disturbance manifested by VWF.     

Surgical anatomy of the radial nerve at the elbow

An anatomical study of the brachial portion of the radial nerve with surgical implications is proposed. Thirty specimens of arm from 20 fresh cadavers (11 male, 9 female) were used to examine the topographical relations of the radial nerve with reference to the following anatomical landmarks: acromion angle, medial and lateral epicondyles, point of division between the lateral and long heads of the triceps brachii, lateral intermuscular septum, site of division of the radial nerve into its superficial and posterior interosseous branches and entry and exit point of the posterior interosseous branch into the supinator muscle. The mean distances between the acromion angle and the medial and lateral levels of crossing the posterior aspect of the humerus were 109 (±11) and 157 (±11) mm, respectively. The mean length and calibre of the nerve in the groove were 59 (±4) and 6 (±1) mm, respectively. The division of the lateral and long heads of the triceps was found at a mean distance of 126 (±13) mm from the acromion angle. The mean distances between the lateral point of crossing the posterior aspect of the humerus and the medial and lateral epicondyles were 125 (±13) and 121 (±13) mm, respectively. The mean distance between the lateral point of crossing the posterior aspect of the humerus and the entry point in the lateral intermuscular septum (LIS) was 29 (±6) mm. The mean distances between the entry point of the nerve in the LIS and the medial and lateral epicondyles were 133 (±14) and 110 (±23) mm, respectively. Our study provides reliable and objective data of surgical anatomy of the radial nerve which should be always kept in mind by surgeons approaching to the surgery of the arm, in order to avoid iatrogenic injuries.     

Effects of weak antagonist on fast elbow flexion movements in man

Summary By using a mathematical model and experiments involving electrical simulation of antagonistic muscles, we have formed the hypothesis (Wierzbicka et al. 1986) that in one-joint movements the antagonist muscle not only provides braking torque but also controls movement time. To get additional experimental support for this hypothesis, we studied elbow flexion movements performed by patients with spinal cord injury at the C 5–6 level who had relatively normal strength in their biceps muscle and little or no voluntary control of the triceps. Seven quadriplegic patients and six control subjects performed elbow flexion movements of 10°, 20°, and 30° as fast and accurately as possible. Despite the lack of antagonist, patients used the same pulse height strategy as control subjects to scale their responses with movement amplitude. However, patients' movement time was on average twice that of control subjects, and durations of both accelerative and decelerative phases of movement were increased. Movement speed and acceleration were reduced to 20–50% of the corresponding values of control subjects. Patients tended to overshoot the target to a larger extent than control subjects, particularly 10° targets, with nearly twice the error. We performed the same experiments using an external torque motor to assist the weak triceps. When a constant extensor torque of 2.5 or 5 Nm was provided by the motor, patients were able to move faster, and movement accuracy improved to within the normal range. These results provide direct evidence that the lack of an antagonist has an important effect on completion time and accuracy of fast goal-directed movements.     

Relation between height and the maximum conduction velocity of the ulnar motor nerve in human subjects

The maximum motor nerve conduction velocity of the right and left ulnar motor nerve was measured in more than 650 healthy medical students of both sexes. There was no side difference in the maximum conduction velocity. The shorter person has a statistically significant higher conduction velocity than the taller person. Comparison of students of both sexes showed a slightly higher conduction velocity in females. However, with regard to its relation to height, the conduction velocity was higher in males.     

A mathematical model for peripheral nerve conduction velocity

OBJECTIVE: To derive a mathematical model for peripheral axon geometry, and apply it to the prediction of latencies along a nerve. DESIGN: Retrospective review of data from individuals with bilaterally normal EMG/NCS, those with a diagnosis of carpal tunnel syndrome alone, and data from previous researchers. SETTING: Electrodiagnostic laboratory at a teaching hospital. SUBJECTS: Twenty-two (22) individuals with bilaterally normal EMG/NCS, and 61 hands from 40 individuals with carpal tunnel syndrome. Data from previous researchers was also utilized. RESULTS: Applying an exponentially tapering axon model to normal data yielded a formula for latency (L = kd 0.775) where k is a constant, and d is the distance from the distal end of the nerve. This formula produced a correlation of 0.777 for predicting median distal motor latencies using the proximal latency, and 0.676 for the ulnar nerve. The largest difference between predicted and actual distal latency was 0.48 msecs for the median nerve and 0.60 msecs for the ulnar nerve. This formula correctly classified as abnormal 3 (37.5%) out of 8 carpal tunnel syndrome cases with completely normal motor studies by standard criteria. This formula also agreed well with the data of other researchers, predicting normal distal latencies, F wave latencies, and identifying abnormal data. CONCLUSIONS: A single model for axon geometry based on uniform exponential tapering accurately predicts latencies for many nerves, and can detect subtle neuropathology.     

Calculation of the conduction velocity of short nerve fibres

The conduction velocity v of a nerve fibre is calculated from the time delay Δ of a propagating action potential between two recording sites along the fibre. However, the conventional method of determining Δ cannot be applied to short nerve fibres. Therefore several linear signal analysis methods for the estimation of Δ have been compared with regard to the reproducibility of their results obtained from pairs of simultaneously recorded action potentials at several small inter-electrode distances. It was found that, estimating Δ from the cross-correlogram and as a second one a variant of this method (maximum likelihood time delay estimation) give the most reliable values of v in short nerve fibres.     

Estimation of nerve conduction velocity using surface multielectrode.

The nerve conduction velocity (NCV) was measured by using the multichannel surface EMG technique. The subjects were 7 healthy volunteers (20-49 years). The evoked responses were recorded from the tibialis anterior muscle when electrically stimulating the common peroneal nerve. The distribution and propagation pattern of the nerve action potentials (NAPs) preceding M-waves could be obtained by the multichannel surface EMG. The NCV of the fastest nerve fibers could be estimated from the time delays of the latencies of the NAPs. The average NCV (ANCV) of active nerve fibers could be also estimated from the time delays of the peak latencies of the NAPs. In 4 of 7 normal subjects, the shortest latencies and the fastest NCVs were obtained with threshold stimulation. The mean values of the NCV and the ANCV with supramaximal stimulation in 7 normal deep peroneal nerves calculated by this method were 55.9 +/- 6.5 m/s and 43.3 +/- 3.2 m/s respectively.