Electrodiagnostic reference values for upper and lower limb nerve

AANEM PRACTICE TOPIC

ELECTRODIAGNOSTIC REFERENCE VALUES FOR UPPER AND LOWER

LIMB NERVE CONDUCTION STUDIES IN ADULT POPULATIONS

SHAN CHEN, MD, PhD,

MICHAEL ANDARY, MD, MS,

RALPH BUSCHBACHER, MD,

DAVID DEL TORO, MD,

BENN SMITH, MD,

YUEN SO, MD,

KUNO ZIMMERMANN, DO, PhD,

and TIMOTHY R. DILLINGHAM, MD

Department of Neurology, Rutgers, the State University of New Jersey, Robert Wood Johnson Medical School, New Brunswick, New

Jersey, USA

Department of Physical Medicine and Rehabilitation, College of Osteopathic Medicine, Michigan State University, East Lansing,

Michigan, USA

Department of Physical Medicine and Rehabilitation, Indiana University, Indianapolis, Indiana, USA

Department of Physical Medicine and Rehabilitation, Medical College of Wisconsin, Milwaukee, Wisconsin, USA

Department of Neurology, Mayo Clinic, Scottsdale, Arizona, USA

Department of Neurology, Stanford University, Stanford, California, USA

Qinqunxx Institute, Rosharon, Texas, USA

Department of Physical Medicine and Rehabilitation, University of Pennsylvania, 1800 Lombard Street, First Floor, Philadelphia,

Pennsylvania 19146, USA

Accepted 26 May 2016

ABSTRACT: Introduction: To address the need for greater

standardization within the field of electrodiagnostic medicine,

the Normative Data Task Force (NDTF) was formed to identify

nerve conduction studies (NCS) in the literature, evaluate them

using consensus-based methodological criteria derived by the

NDTF, and identify those suitable as a resource for NCS met-

rics. Methods: A comprehensive literature search was con-

ducted of published peer-reviewed scientific articles for 11

routinely performed sensory and motor NCS from 1990 to

2012. Results: Over 7,500 articles were found. After review

using consensus-based methodological criteria, only 1 study

each met all quality criteria for 10 nerves. Conclusion: The

NDTF selected only those studies that met all quality criteria

and were considered suitable as a clinical resource for

NCS metrics. The literature is, however, limited and these find-

ings should be confirmed by larger, multicenter collaborative

efforts.

Muscle Nerve 54: 371–377, 2016

Electrodiagnostic (EDx) testing is used extensively

to diagnose neuromuscular disorders but a univer-

sal standard for nerve conduction studies (NCS) is

not available.

1,2

Individual laboratories have been

encouraged to use their own techniques for per-

forming NCS and develop their own reference

data, “despite inherent methodological and statisti-

cal challenges with this approach.” Other EDx

physicians and laboratories have relied on refer-

ence data in textbooks or values passed along by

academic teaching laboratories. However, many

published studies

do not meet contemporary sta-

tistical and methodological standards. Nerve con-

duction testing can be challenging and is

dependent upon the skill of the EDx practi-

tioners,

instrumentation, and testing circumstan-

ces that have been discussed.

1,2

The American

Association of Neuromuscular & Electrodiagnostic

Medicine (AANEM) formed the Normative Data

Task Force (NDTF) to establish a set of evidence-

based criteria to screen the peer-reviewed pub-

lished literature.

1,2

The NDTF’s report details the

results of the review and selection of suitable

articles regarding 11 routinely studied nerves.

METHODS

A literature search was conducted on all studies

published in English or other languages translated

into English from 1990 to 2012 using the words “nerve

conduction” or “nerve conduction studies,” and the

names of the 11 sensory and motor nerves routinely

tested in the upper and lower extremities in the fol-

lowing databases: PubMed/Medline; EMBASE; Web

of Science; and Scopus. Speciﬁcally, the search terms

for the studied nerves included “radial sensory,”

“median sensory,” “ulnar sensory,” “median motor,”

“ulnar motor,” “medial antebrachial cutaneous,”

“lateral antebrachial cutaneous,” “sural,” “superﬁcial

peroneal,” “peroneal motor,” and “tibial motor.”

All studies identiﬁed by the initial search were

reviewed by an AANEM administrative staff mem-

ber or an NDTF member (Table 1) to determine

whether there was a sample size of >100 healthy

subjects.

Abstracts that met the sample size inclu-

sion criteria were then reviewed by an NDTF

Abbreviations: AANEM, American Association of Neuromuscular & Elec-

trodiagnostic Medicine; ADFN, accessory deep fibular motor nerve; EDx,

electrodiagnostic; NCS, nerve conduction study; NCV, nerve conduction

velocity; NDTF, Normative Data Task Force

Key words: guidelines; nerve conduction; nerve conduction studies; nor-

mal values; normative data; reference values; standards of practice

Disclaimer: This article was prepared and reviewed by the American

Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) and

did not undergo separate peer review by Muscle & Nerve. Reviewed by

the AANEM Practice Issue Review Panel, April 2016. Approved by the

AANEM Board of Directors, April 2016.

Correspondence to: T.R. Dillingham; e-mail: timothy.dillingham@uphs.

upenn.edu

2016 American Association of Neuromuscular and Electrodiagnostic

Medicine

Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.

1002/mus.25203

AANEM Practice Topic MUSCLE & NERVE September 2016 371

member assigned to that particular nerve. Full

articles were obtained and reviewed in detail to

determine whether they were focused on deriving

normative data and if they appeared to meet

NDTF criteria. Articles that appeared to meet most

of the NDTF criteria were circulated to all mem-

bers for review. The members discussed each

review either in person or through e-mail. A stand-

ardized grading form was used to grade each arti-

cle. The techniques, statistical methods,

instrumentation, and study design were rated

based on 7 NDTF criteria as deﬁned in an accom-

panying article.

RESULTS

Over 7,500 studies were found dealing with 11

sensory and motor nerves (Table 1), and a total of

401 met the sample size criterion of >100 healthy

subjects. An initial evaluation of the articles led to

a recommendation that 83 undergo detailed

review. Studies that met all NDTF criteria were

identiﬁed, and results for each sensory or motor

nerve are described in Tables 2–5.

Sensory Nerves. Among sensory nerves, 1 article

met all NDTF criteria for: (1) superﬁcial radial sen-

sory nerve

; (2) median sensory nerve

; (3) ulnar

sensory nerve

; (4) medial antebrachial cutaneous

sensory nerve

; (5) lateral antebrachial cutaneous

sensory nerve

; and (6) sural sensory nerve.

The superﬁcial ﬁbular (peroneal) sensory nerve

was the only sensory nerve for which no studies

met NDTF criteria. The articles, their speciﬁc test-

ing conditions, and EDx parameters are outlined

in Tables 1–3.

In the sural nerve study chosen by the NDTF,

nerve responses were absent bilaterally in 4 per-

sons and were unilaterally absent in 4 others, yield-

ing recordable sural responses on both sides in

97% of subjects.

Sensory nerve conduction veloc-

ities were not calculated in the study selected, and

another study was cited that examined conduction

velocity but did not meet all NDTF criteria.

9,10

Quantile regression was used by this group to pro-

vide reference values (cut-offs) for velocities. The

third percentiles (lowest cut-off for normality)

were 43 m/s, 45 m/s, and 50 m/s for median,

ulnar, and radial sensory nerves, respectively. The

lower limit of normal for the sural sensory nerve

was 40 m/s. Median and ulnar sensory nerve

amplitudes were inﬂuenced by age and body mass

index (BMI) and these subgroups are shown in

table 3.

Motor Nerves. For the median motor nerve, 1,111

articles were initially identiﬁed, and 25 studies

were sent for NDTF review; only 3 met most of the

NDTF criteria, and 1 article met all criteria.

This

study included 249 subjects and considered the

effects of age, gender, and height on the NCS

parameters; separate reference data were provided

Table 1. Identification process for selecting studies meeting the Normative Data Taskforce (NDTF) criteria from the published literature

spanning 1990–2012.

Number of articles identified

results

Initial

review

NDTF

review

Final selected studies (first author and year) for reference

values [other studies with useful information]

Upper extremity nerves

Superficial radial sensory 418 18 5 Evanoff 2006

[Benatar 2009

]

Median sensory 1,326 101 9 Buschbacher 1999

[Grossart 2006,

* Falco 1992

]

Ulnar sensory 940 40 12 Buschbacher 1999

[Grossart 2006,

* Benatar 2009

]

Medial antebrachial cutaneous sensory 65 11 3 Prahlow 2006

Lateral antebrachial cutaneous sensory 91 10 6 Buschbacher 2000

Median motor 1,111 43 25 Buschbacher 1999

(to the abductor pollicis brevis) [Grossart

2006,

* Foley 2006

(to the pronator quadratus), Foley

2006

(to the pronator teres/flexor carpi radialis)]

Ulnar motor 1,211 47 5 Buschbacher 1999

[Grossart 2006,

* Ehler 2013,

Falco 1992

]

Lower extremity nerves

Sural sensory nerve 1,512 23 7 Buschbacher 2003

[Falco 1994

]

Superficial fibular (peroneal) sensory 157 33 2 No primary article was found that sufficiently met the criteria for

quality [Kushnir 2005,

Falco 1994

]

Fibular (peroneal) motor 161 65 5 Buschbacher 1999

[Mathis 2011

(to the accessory peroneal)]

Tibial motor 539 10 4 Buschbacher 1999

(to the abductor hallicus), Buschbacher

1999

(to the flexor digiti minimi brevis)

Total 7,531 401 83

Articles in italics are those that did not meet all NDTF criteria, but contain potentially useful information.

*Studies of median and ulnar comparison analyses from the primary studies, yet published separately. Findings were derived from the primary sample using

the same methodology, inclusion criteria, and statistical analyses.

372 AANEM Practice Topic MUSCLE & NERVE September 2016

if the effect of the relevant variable was signiﬁcant

at P  0.01. For amplitude, age but not gender

was found to be relevant, and these reference

values are shown in Table 4. For both latencies

and conduction velocities, gender and age were

found to have small but signiﬁcant effects, and

these subgroups are shown in Table 4. Height had

no signiﬁcant effect on the median motor NCS

parameters.

Two other articles that met all crite-

ria examined median motor nerve conduction to

the pronator quadratus

and to the pronator teres

and ﬂexor carpi radialis muscles.

Fortheulnarmotornerve,1,211articleswere

initially identiﬁed, and 1 article met all criteria

(Table 4). There were no age or gender effects,

thus the tabulated nerve conduction parameters,

including velocity changes across the elbow, are

shown in Table 4. The upper limits of nerve

Table 2. Standardized techniques for major motor and sensory nerve conduction studies in adults.

Techniques (recommend) Machine Settings

Electrode placement: ground electrode always placed

between the stimulating and recording electrodes

Nerves G1 G2 Stimulating site (SS)

Distance

(G1 to SS)

(cm)

Display

sensitivity

(lV/div) sensory,

(mV/div) motor

Sweep

(ms/div)

Superficial radial

sensory

Extensor pollicis longus

tendon

Base of thumb Along the radius 10 5–10 1

Median sensory Index finger 4 cm distal to G1 Wrist: between the flexor carpi

radialis and the palmaris longus

tendons

14 20 1

Slightly distal to the second

MCP

Palm: midway between the

14-cm stimulation point

and G1

Ulnar sensory Fifth digit 4 cm distal to G1 Slightly to the radial side of the

flexor carpi ulnaris tendon

14 20 1

Slightly distal to the fifth

MCP

Medial antebrachial

cutaneous sensory

Medial forearm Distal: 3 cm bar Midway between the medial epi-

condyle and the distal biceps

tendon

10 10 1

Lateral antebrachial

cutaneous sensory

On a line to the radial

pulse

Distal: 3 cm bar Just lateral to the distal biceps

tendon

10 10 1

Median motor Abductor pollicis brevis

motor point

Distal to first MCP Wrist: between the flexor carpi

radialis and the palmaris longus

tendons

852

Midpoint of wrist crease

and the first MCP

Elbow: medial to the brachial pulse

Ulnar motor Hypothenar eminence Slightly distal to the

fifth MCP joint

Wrist: slightly radial to the flexor

carpi ulnaris tendon

852

Halfway between the

pisiform and the

MCP

Elbow flexion to 908 Below elbow: 4 cm distal to the

medial epicondyle

Above elbow: 10 cm proximal to

the below-elbow site, measured

in a curve behind the medial

epicondyle to a point slightly

volar to the triceps muscle

Axillary: 10 cm proximal to above-

elbow site

Sural sensory Posteroinferior to the

lateral malleolus

Distal: 3 cm bar At or slightly lateral to the calf

midline

14 2–5 1

Peroneal (fibular)

motor

Midpoint of extensor

digitorum brevis

Just distal to

fifth MTP

Ankle: lateral to the tibialis

anterior tendon

855

Below fibular head: posteroinferior

to the fibular head

Above fibular head: 10 cm proxi-

mal to the below fibular head

site and slightly medial to the

tendon of the biceps femoris

Tibial motor Medial foot (slightly

anterior/inferior to the

navicular tubercle)

Slightly distal to

first MTP (medial

aspect of joint)

Ankle: posterior to the medial

malleolus

855

Knee: midpopliteal fossa

For all studies, temperature was maintained above 328C for the upper extremity and above 318 C for the lower extremity. The temperature was measured

on the dorsum of the hand for all upper limb NCS, both motor and sensory. Temperature was recorded over the dorsum of the foot for the sural sensory,

tibial motor, and peroneal (fibular) motor nerve conduction. Sensory nerve studies: Frequency filters at 20 H

Z (low) and 2 kHZ (high). Motor nerve studies:

Frequency filters at 2–3 H

Z (low) and 10 kHZ (high). MCP, metacarpopha langeal joint; MTP, metatarsophalangeal joint.

AANEM Practice Topic MUSCLE & NERVE September 2016 373

conduction velocity slowing from below elbow to

across elbow were 15m/s or 23%, providing ref-

erence values useful in assessing for suspected

ulnar neuropathy at the elbow.

The ﬁbular (peroneal) motor nerve literature

review revealed 161 studies, and 1 article that stud-

ied the ﬁbular (peroneal) motor nerve to the

extensor digitorum brevis muscle was selected.

This study of 242 subjects considered the inﬂuence

of age and height as well as side-to-side and seg-

mental differences. Increasing height was found to

correlate with decreasing conduction velocity, and

increasing age was found to correlate with

decreases in both conduction velocity and

amplitude (Table 4). The upper limit (at the 97th

percentile) of normal drop in velocity from the

lower leg to the across-knee segment was 6 m/s or

12%, and the upper limit of normal drop in ampli-

tudes from below to above the ﬁbular head was

25%.

Of note, the amplitude in the older

age category was less than half that of the younger

age group (Table 4).

One study

examined both the accessory deep

ﬁbular (peroneal) motor nerve [ADPN, a branch

of superﬁcial ﬁbular (peroneal) motor nerve] and

the deep ﬁbular (peroneal) motor nerve conduc-

tion to the extensor digitorum brevis muscle in

200 subjects. This article is mentioned because it

contains information regarding the prevalence of

the ADPN in normal individuals, which is 13.5%.

For the tibial motor nerve, 539 studies were ini-

tially identiﬁed, and 2 met all NDTF criteria. One

article that studied tibial motor nerve conduction

to the abductor hallucis was selected.

This study

of 250 subjects considered the inﬂuence of inde-

pendent variables of age, gender, and height on

the NCS parameters and included side-to-side and

segmental differences. Similar to the ﬁbular motor

Table 3. Reference values for 6 major sensory nerve conduction studies in adults.

Nerves

Amplitude: lower limit (3rd percentile) (lV)

Latency: upper limit (97th

percentile) (ms)

Size (N) Onset-to-peak Peak-to-peak Onset Peak

Superficial radial sensory

(antidromic, 10 cm)

212

7 11 2.2 2.8

Median sensory*

(antidromic to second digit,

wrist 14 cm, palm 7 cm)

258

11 (wrist) 13 (wrist) 3.3 (wrist) 4 (wrist)

6 (palm) 8 (palm) 1.6 (palm) 2.3 (palm)

Amplitude (wrist) by age and BMI

†

(19–49)

BMI <24

17 19

(19–49)

BMI 24

11 13

(50–79)

BMI <24

915

(50–79)

BMI 24

Ulnar sensory (antidromic

to fifth digit, 14 cm)

258

10 9 3.1 4.0

Amplitude (wrist) by age and BMI

†

(19–49)

BMI <24

14 13

(19–49)

BMI 24

11 8

(50–79)

BMI <24

10 13

(50–79)

BMI 24

Medial antebrachial cutaneous sensory

(antidromic, 10 cm)

207

4 3 2.6

Lateral antebrachial cutaneous sensory

(antidromic, 10 cm)

213

5 6 2.5

Sural sensory (antidromic, 14 cm) 230

4 4 3.6 4.5

BMIs calculated as follows: BMI 5 (W/H

), where W is the patient’s weight (in kilograms) and H is the patient’s height (in meters).

*Median sensory NCS data shown were recorded at digit 2. Normative data recorded at digit 3 are also available in the same article.

The digit 3 findings

are similar in magnitude to data derived from digit 2.

†

The lower limits of onset-to-peak and peak-to-peak amplitudes are shown as mean – 2 SD, showing the statistically significant effects of age and BMI on

the amplitudes of the median and ulnar sensory nerves at the wrist (P < 0.01). Data sets normalized by square-root transformation.

374 AANEM Practice Topic MUSCLE & NERVE September 2016

nerve,

increasing height was found to correlate

with decreasing conduction velocity, and increas-

ing age was found to correlate with decreases in

velocity and amplitude (Table 4). The upper limit

of normal drop in amplitude from the ankle to

the knee was 10.3 mV, or 71% (larger than the ﬁb-

ular motor segmental drop).

This degree of

amplitude drop is unusual and surprising to some

clinicians. It can be misinterpreted to represent

conduction block due to demyelinating neuropa-

thy. This amplitude drop in normal subjects is

most likely due to temporal dispersion and phase

cancellation between the multiple distal tibial-

innervated foot muscles recorded by the reference

electrode.

One other article also met all the crite-

ria and evaluated the lateral tibial motor nerve

conduction to the ﬂexor digit minimi brevis mus-

cle, a less commonly used technique for testing

this nerve.

Median-to-Ulnar and Ulnar-to-Median Motor and Sen-

sory Nerve Comparisons.

Comparisons of median

and ulnar motor nerve conduction across the wrist,

(intra-hand comparisons) are helpful in minimiz-

ing the confounding effects of age, height, and

limb temperature. A comparison of these latency

comparisons provides reference values and utilizes

the same methodology, sample, and non-

parametric statistics as in the main articles (Table

5).

The distribution of median-to-ulnar motor

latency comparisons differed from ulnar-to-median

motor latency comparisons. For the median-to-

Table 4. Reference values for 4 major motor nerve conduction studies in adults.

Distal amplitude (mV) Conduction velocity (m/s) Distal latency (ms)

Nerves

Size

(N) Subgroups

Low

limit

3rd% Subgroups

Low

limit

3rd% Subgroups

Upper

limit

97th%

Median

motor

249

All ages 4.1* All ages 49* All ages 4.5*

Amplitude by age CV by age and gender Distal latency by age and gender

19–39 y 5.9 19–39 y, men 49 19–49 y, men 4.6

40–59 y 4.2 19–39 y, women 53 19–49 y, women 4.4

60–79 y 3.8 40–79 y, men 47 50–79 y, men 4.7

40–79 y, women 51 50–79 y, women 4.4

Ulnar

motor

248

All ages 7.9* Below elbow 52* All ages 3.7*

Across elbow 43*

Above elbow 50*

CV drop across the elbow 15*

CV drop across the elbow (%) 23%*

Fibular

(peroneal)

motor

242

All ages 1.3* CV ankle to below

fibular head

38* All ages 6.5*

CV ankle to below fibular head

by age and height

19–39 y, <170 cm 43

19–39 y, >170 cm 37

40–79 y, <170 cm 39

40–79 y, >170 cm 36

Amplitude by age

19–39 y 2.6 CV across fibular head 42*

40–79 y 1.1 CV drop across the

fibular head

% drop in amplitude from

ankle to below fibula

32%*

% drop in amplitude

across fibular head

25%* % drop in CV across

fibular head

12%*

Tibial

motor

250

All ages 4.4* All ages 39* All ages 6.1*

Amplitude by age CV by age and height

19–29 y 5.8 19–49 y, <160 cm 44

30–59 y 5.3 19–49 y, 160–170 cm 42

60–79 y 1.1 19–49 y, 170 cm 37

Amplitude drop from

ankle to knee

10.3* 50–79 y, <160 cm 40

% drop in amplitude

from ankle to knee

71%* 50–79 y, 160–170 cm

50–79 y, 170 cm

*Values for the entire sample for each nerve encompassing all ages.

AANEM Practice Topic MUSCLE & NERVE September 2016 375

ulnar motor comparisons, when the median nerve

was investigated, the maximal difference (97th per-

centile) in onset latency for persons age <50 years

was 1.4 ms and for patients age >50 years it was

1.7 ms. In contrast, when the ulnar nerve was the

nerve of interest, the ulnar-to-median latency com-

parison was 0.0 ms for the younger group and –0.3

ms for the older group. This means that the ulnar

motor latency should not be longer than the

median motor latency. If it is, then ulnar nerve

pathology across the wrist may be present.

Median and ulnar sensory nerve latency compari-

sons, in contrast to the motor nerve comparisons,

did not show a substantial age inﬂuence. For the

entire group, the median-to-ulnar peak latency

comparison had an upper (97th percentile)

limit of 0.4 ms, whereas the ulnar-to-median

upper limit comparison was similar at 0.5 ms

(Table 5).

DISCUSSION

The NDTF ﬁrst developed standardized criteria

and then applied the criteria to screen and review

the published literature dealing with normative

results for 11 routinely performed sensory and

motor NCS in the upper and lower extremities.

The techniques and instrument settings used in

these studies are readily programmed into modern

EDx equipment and are easily duplicated.

After review of >7,500 studies, 401 had the

required sample sizes of >100, and 10 studies were

identiﬁed for the 11 nerves (a single acceptable

study for each nerve). The reasons that so few

studies met these criteria are likely multifactorial.

Conducting large-scale normative studies is time-

consuming and requires signiﬁcant resources,

meeting a sample size of >100 subjects is daunt-

ing, and funding sources are limited. Many studies

obtained reference data in the context of studying

a target disorder and used healthy subjects as a

control. Data from many studies did not address

the non-Gaussian distribution of NCS parameters

and often derived cut-off values using the mean

and standard deviations rather than percentiles.

The ﬁnal selected studies emanated from a sin-

gle research group and have both strengths and lim-

itations. Sample sizes were all >200 subjects and

provided statistical power to the analyses. These

analyses included multiple covariates known to

inﬂuence NCS parameters: age; gender; body mass

index; and height. The studies, however, reﬂect

ﬁndings from a single regional population of

healthy adults and a single EDx laboratory. Future

studies from other laboratories that sample subjects

from other geographical regions will be necessary to

validate these data and fully conﬁrm the level of

generalizability for the results. Until such data are

available, EDx physicians may use these normative

data now in their clinical practices.

Future studies of this type or a laboratory wish-

ing to develop its own set of metrics should utilize

the NDTF criteria to carefully address testing

methods and study design. These NDTF selection

criteria can assist journal editors and reviewers

when evaluating manuscripts submitted for

publication.

The NDTF limited the scope of the work to

commonly tested nerves in adult populations.

Future efforts should address reference values for

less commonly tested nerves and should include

late responses (F-waves and H-reﬂexes) and studies

on pediatric populations.

In the future, a multicenter study with a larger

and more geographically and ethnically diverse

sample would be useful to better clarify the gener-

alizability of these studies and more precisely

examine the important inﬂuences of age, gender,

height, and body mass index on clinical NCS

parameters.

CONCLUSIONS

The NDTF used consensus criteria to systemati-

cally review published studies on NCS on 11 com-

monly tested nerves and identiﬁed only 1 study

that met all criteria for each of the 10 nerves. This

Table 5. Median and ulnar latency differences for sensory and motor nerves.

Differences in sensory latencies

(ms) between nerves*

Differences in motor latencies (ms) between

nerves by age group

†

Onset latency Peak latency Ages 19–49 y Ages 50–79 y All

Median compared with (minus) ulnar 0.5 0.4 1.4 1.7 1.5

Ulnar compared with (minus) median 0.3 0.5 0.0 20.3 0.0

*Upper limit of normal is the 97th percentile of the observed differences distribution. There were no age effects, thus the data are combined. Differences in

sensory latencies are shown with wrist stimulation over the median nerve at 14 cm recording over digit 3, and stimulation over the ulnar nerve at 14 cm

recording over digit 5.

†

Upper limit of normal is the 97th percentile of the observed differences distribution for the onset latency. There were age effects, thus cut-offs are shown

by age subgroups. Differences in motor latencies are shown with wrist stimulation over each nerve at 8 cm from recording electrodes over abductor pollicis

brevis for median and abductor digiti minimi for ulnar.

376 AANEM Practice Topic MUSCLE & NERVE September 2016

limited set of reference metrics may be suitable for

consideration for use by EDx practitioners.

The NDTF gratefully acknowledges the assistance of the AANEM

Practice Issue Review Panel for review and critique of the manu-

script. The NDTF also acknowledges Carrie Winter, Shirlyn

Adkins, Seng Vang, Catherine French, and Adam Blaszkiewicz for

their tireless administrative support of this project. The authors

thank Larry Robinson, MD, and William Litchy, MD, for their

thoughtful input in the early stages of this project. We also thank

Katie McCausland, DO, for assistance with the ulnar and ﬁbular

(peroneal) motor nerves.

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