Deriving reference values in electrodiagnostic medicine

Traditional methods for determining nerve conduction reference values have usually involved studying a group of normal controls, and determining the mean ± 2 standard deviations (SD) for each parameter. Recent studies suggest other factors should be taken into account. Height has a greater effect on conduction velocity than age or temperature. The common assumption that conduction values follow a normal, bell-shaped Gaussian distribution appears unwarranted. The curve for some conduction parameters is significantly skewed, making a mean ± 2 SD definition of normality inaccurate to a clinically important degree. In developing and using reference values one should consider height, age, and temperature, and calculate the mean ± 2 SD of the transformed data to remove the effects of skew. Reference values provide only a guide to the probability a given result came from a healthy or diseased individual; one should therefore seek multiple internally consistent abnormalities before diagnosing disease on the basis of electroneurography. © 1993 John Wiley & Sons, Inc.     

Hand-held myometry: reference values.

In thirteen major muscle groups of 50 healthy females and 50 males, aged 20-60 years, maximum voluntary contraction was measured with a hand-held dynamometer. The intrasession variation, the left-right variation, and the fifth and fiftieth centile values were calculated. The ratio of two observations within one session ranged from 0.85 to 1.18 and the ratio of left to right ranged from 0.82 to 1.22 (95% reference limits). In 20 volunteers the repeatability was tested after one week. The ratio of averages of three measurements in two successive weeks ranged from 0.82 to 1.23 (95% reference limits). There were only small differences between muscle groups concerning these ratios. A significant relation with age and weight/Quetelet Index could be demonstrated in some muscle groups. The mean strength of females is approximately two thirds of the strength of males. The data may be useful as reference values in the application of hand-held myometry.     

Cross-sectional area reference values for nerve ultrasonography

Ultrasound allows for a non-invasive structural assessment of nerves, muscles, and surrounding tissues, and therefore it is increasingly being used as a supplement to traditional electrodiagnostic studies. As investigators have begun to use ultrasound to explore peripheral nerves, it has become clear that conditions such as entrapment, hereditary neuropathies, acquired neuropathies, trauma, and nerve tumors result in an increase in nerve cross-sectional area. Reference values have not been published for the cross-sectional area of many nerves commonly studied in diseases of the peripheral nervous system, so our goal was to obtain reference values for the nerve cross-sectional area at the following sites: radial at antecubital fossa; radial at distal spiral groove; musculocutaneous in upper arm; trunks of the brachial plexus; vagus at carotid bifurcation; sciatic in distal thigh; tibial in popliteal fossa; tibial in proximal calf; tibial at ankle; peroneal in popliteal fossa; peroneal at fibular head; and sural in distal calf. Mean cross-sectional area, as well as side-to-side differences, are reported for each site, and qualitative data are provided to guide imaging at each site. The information provided in this study should serve as the starting point for quantitatively evaluating these nerve sites with ultrasound.     

Dorsal ulnar cutaneous nerve conduction: reference values

We investigated the reference values of the dorsal ulnar cutaneous nerve (DUC) sensory nerve conduction (SNC) in 66 healthy individuals. Measurements were processed using stimulating electrodes positioned between the ulnar bone and the flexor carpi ulnaris muscle, 11-13 cm proximal to the active electrode recording. Superficial recording electrodes were placed on the fourth intermetacarpal space. The mean sensory conduction velocity (SCV) in males was 63.7 - 0.16 x age +/- 3.36 m/s and in females was 57.7 +/- 3.37 m/s. The mean sensory nerve action potential (SNAP) amplitude in males was 19.5 +/- 10.7 microV and in females was 24.6 +/- 5.8 microV. The mean SNAP duration was 0.96 +/- 0.13 ms. No significant differences regarding the DUC-SCV, distal latency, and SNAP duration or amplitude were found between both sides of the same subject. The amplitude of the SNAP was higher in females than males. The effects of age on DUC-SCV were distinct for each gender.     

Single fiber EMG reference values: A collaborative effort

Single fiber electromyography (SFEMG) measurements of fiber density and jitter are used in the diagnosis of a variety of peripheral nervous system disorders. However, the normal values of these measurements for most muscles and age groups are not well documented in the literature. We present a retrospective and prospective multicenter collection of SFEMG jitter and fiber density data from control subjects obtained for the purpose of defining reference values for many muscles and different ages. The data and calculated upper limits for fiber density, individual pair jitter, and mean jitter are presented for each muscle in tabular and graphical format, for different age groups.     

高频超声对上肢桡神经检测正常参考值的研究

目的测量正常人上肢桡神经在高频超声(HUS)下神经形态、声像学特点及横截面积(CSA)的正常值并探讨神经与周围组织的关系;为高频超声检侧外周神经疾病提供正常参考值。方法对临床检查正常的200例健康志愿者沿桡神经在神经预定的测量点上依次获取超声声像图及测量各点神经的横截面积,每个测量点重复测量三次取其平均值,并做神经CSA与身高、体重的相关性分析。结论高频超声下正常人上肢神经呈筛网状低回声图像,横截面呈圆形、卵圆形或三角形。测量桡神经各测量点处的神经横截面积,桡神经在肱骨外髁上4cm、桡神经沟处2点面积依次为(x珋±S)5.14±1.24 mm2、5.08±1.23mm2。左右上肢之间同一测量点比较神经横截面积P>0.05,桡神经的CSAs同年龄组男女之间比较P<0.05,桡神经在青、中、老三组CSA相比P>0.05。桡神经横截面积与身高、体重呈正相关性。桡神经横截面积与体重的最大相关系数是0.36(P<0.01),与身高的最大相关性系数是0.38(P<0.01)。结论桡神经在不同测量点其正常值不同,CSAs在性别对比中存在差异,青、中、老三组对比CSAs无差异,身高、体重与神经的大小呈正相关性。     

Sensory thresholds in older adults: Reproducibility and reference values

To evaluate the test–retest reproducibility of vibratory perception (VPT) and thermal discrimination (TDT) thresholds on the foot in older adults, we examined 20 50–76-year-old subjects with, and 19 without noninsulin-dependent diabetes mellitus. Adjusted reference values for both thresholds were obtained by assessing the relations with age, body height, and sex among 216 subjects with normal glucose tolerance, of the same age, sampled randomly from a geographically defined general population. The VPT appeared to be more reproducible than the TDT (reliability coefficient 0.89 vs. 0.54). The reproducibility of the VPT was inversely related to age and better for men than for women. Diabetes and glycemic level did not affect the reproducibility of either threshold. Both thresholds were related to age and height. Women had a higher VPT than men. The relations between sex and sensory thresholds at the lower limb, reported in previous studies, were probably confounded by height. © 1994 John Wiley & Sons, Inc.     

Measurement of reference values for certain proteins in cerebrospinal fluid

Reference values are presented for certain cerebrospinal fluid proteins and related indexes, based on determinations carried out on 46 patients with diffuse lower back pain using radial immunodiffusion and electroimmunoassay. A sex difference was noted in total protein and albumin values. The electroimmunoassay method with its sensitivity enhanced by the use of Coomassie Blue staining and optimal antiserum concentrations enabled a reference value to be determined for IgA in cerebrospinal fluid.     

Cerebrospinal fluid IgG in childhood: the establishment of reference values

A retrospective analysis of quantitative and qualitative immunoglobulin G (IgG) results from 253 children who were either medically and neurologically normal or highly unlikely to have abnormalities of CSF IgG is reported. Normal values in this reference population vary with age for CSF/albumin IgG ratio and CSF/serum IgG index and are significantly different from the adult reference values. The rate of false positivity is lower for quantitative values than for qualitative IgG determinations (oligoclonal bands).     

Radial Nerve F-wave reference values with surface electrodes from the anconeus muscle

Introduction: We sought to obtain normative values for radial nerve F-wave variables, recording with surface electrodes from the anconeus muscle. Methods: We tested 30 healthy participants (17 women, 13 men) and measured the following variables: number of F waves/40 traces (F%); minimum, maximum, and mean F-wave latency (FMIN, FMAX, FMED, respectively); F-wave chronodispersion (FCHR); interside differences of F% and FMIN (DF% and DFMIN, respectively). Results: The mean F% was 41.3%; the normative values of FMIN, FMED, FMAX, and FCHR were < 21.2, <22.1, <23.3, and < 4.0 ms, respectively; and normative values of DF% and DFMIN were < 16.6% and < 1.1 ms, respectively. Height was the sole independent predictor in a regression model of FMIN, FMED, and FMAX; this explained 37%–44% of the variability. Discussion: We identified a feasible and useful technique to record radial nerve F waves from the anconeus muscle and obtained normative values of F-wave variables. Muscle Nerve 59 :244–246, 2019     

Sural/radial nerve amplitude ratio: reference values in healthy subjects

The sural/radial nerve amplitude ratio (SRAR) has been proposed as a sensitive indicator of early-stage axonal polyneuropathy. However, previous studies did not take into account the effect of sex differences or different calculating methods. To obtain reference values and information on the variability of the SRAR in daily practice, we measured amplitudes of sural and superficial radial sensory nerve action potentials in 106 healthy adults, correlated them with epidemiological variables, and calculated the SRAR in several ways. Our results show that the SRAR is a robust measure, independent of age, weight, sex, or method of calculation. The use of bilateral measurements is recommended. The cut-off value (5th percentile) of 0.2 in these healthy subjects is much lower than found previously, especially compared to defining cut-off values by comparing patients with matched controls. Further study is needed to establish the clinical value of this SRAR in the early detection of axonal polyneuropathies.     

Normal controls and biological reference values in child psychiatry: defining normal

About half of adults volunteering as normal control research subjects may be rejected because of significant psychopathology, but no parallel study has been done to date for pediatric subjects. Of 152 applicants (ages 6 to 18) for participation as paid normal controls, 44% were found ineligible and at least 31.8% of the child volunteers had probable or certain psychiatric disorders. Successive screenings, including rating scales and structured interviews, were necessary to obtain controls meeting a defined standard of psychiatric health. Careful scrutiny of child volunteers in biological psychiatric research is needed to assure meaningful comparisons.     

Ultrasonographic reference values for assessing normal radial nerve ultrasonography in the normal population

High-resolution ultrasound has been used recently to characterize median and ulnar nerves,but is seldom used to characterize radial nerves.The radial nerve is more frequently involved in entrapment syndromes than the ulnar and median nerves.However,the reference standard for normal radial nerves has not been established.Thus,this study measured the cross-sectional areas of radial nerves of 200 healthy male or female volunteers,aged 18 to 75,using high-resolution ultrasound.The results showed that mean cross-sectional areas of radial nerves at 4 cm upon the lateral epicondyle of the humerus and mid-humerus(midpoint between the elbow crease and axilla) were 5.14 ± 1.24 and 5.08 ± 1.23 mm2,respectively.The age and the dominant side did not affect the results,but the above-mentioned cross-sectional areas were larger in males(5.31 ± 1.25 and 5.19 ± 1.23 mm2) than in females(4.93 ± 1.21 and 4.93 ± 1.23 mm2,respectively).In addition,the cross-sectional areas of radial nerves were positively correlated with height and weight(r = 0.38,0.36,respectively,both P 0.05).These data provide basic clinical data for the use of high-resolution ultrasound for the future diagnosis,treatment,and prognostic evaluation of peripheral neuropathies.     

Cross sectional area reference values for sonography of peripheral nerves and brachial plexus

ObjectiveUltrasound measurements of the cross sectional area (CSA) variability have been recently introduced to quantify pathological changes in peripheral nerves (PN).MethodsReference values from 75 healthy subjects and their correlation to age, height, weight and sex are reported.ResultsThe mean values in PN were: (1) intranerve CSA-variability: median 1.05 (SD ± 0.13), ulnar 1.53 (SD ± 0.51), fibular 1.33 (SD ± 0.37), tibial 1.39 (SD ± 0.39), (2) internerve CSA-variability 1.76 (SD ± 0.37), (3) intraplexus CSA-variability 1.52 (SD ± 0.37), (4) side-to-side difference ratio of the CSA-variability: median 1.21 (SD ± 0.04), ulnar 1.2 (SD ± 0.25), fibular 1.19 (SD ± 0.23), tibial 1.28 (SD ± 0.24) and brachial plexus 1.19 (SD ± 0.23). CSA did not correlate with height in PN, but correlated with weight in the ulnar nerve [Guyon’s canal, r = 0.411, p = 0.0237, elbow r = 0.409, p = 0.0248]. Significant changes between sex were found only in the ulnar (Guyon’s canal, p = 0.0265), fibular (popliteal fossa, p = 0.0336) and sural nerve (p = 0.048). CSA decreased with age in the median (axilla, p = 0.0236), and radial nerve (spiral groove, p = 0.0037) and increased in the tibial nerve (ankle, p < 0.0001).ConclusionsThe CSA reference values reported seem to correlate at certain sites with age, weight and sex but not with height.SignificanceThe new CSA variability measures may be helpful in investigating pathologies of the PN.