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Wrist – Digit II, Wrist – Digit V

Surface Recording Technique, Antidromic Study
  • Giuliano Gentili
  • Mario Di Napoli
Chapter

Original Settings

Sensitivity was 20 μV/division, sweep speed was 2 ms/division, duration of pulse was 0.1–0.4 ms, and the machine used was a Tektronix electromyograph. Low-frequency filter, high-frequency filter, and rate of pulse were not specified.

Position

This study was performed in the supine position.

Recording

Following the antidromic method [1], signals were recorded using surface electrodes from the median and ulnar nerves separately (Fig. 1). For the median nerve (R1), the active recording electrode (A) was placed around the proximal interphalangeal joint of digit II; the reference electrode (R) was placed over the distal interphalangeal joint of digit II. For the ulnar nerve (R2), the active recording electrode (A) was placed around the proximal interphalangeal joint of digit V; the reference electrode (R) was placed over the distal interphalangeal joint of digit V. The proximal interphalangeal joint rather than the base of the finger was selected as the site for the proximal ring electrode to reduce or eliminate the volume-conducted motor response. Adjacent digits were kept from inadvertently contacting each other. Ground (G) was placed on the dorsum of the hand, between the recording and the stimulating electrodes (the figure shows the ground electrode placed on the palm). The author used the same technique described previously [2].
Fig. 1

Antidromic sensory nerve action potentials (SNAPs) recorded to digit II (upper trace) and to digit V (lower trace), stimulation of the median and ulnar nerves at the wrist

Stimulation

Stimulations were applied over the median and ulnar nerves at the wrist. Median and ulnar nerves were stimulated separately (S1, S2), both at 14 cm from the active recording electrode (A) placed around the proximal interphalangeal joint of digit II (R1) and digit V (R2). The cathodes were placed proximally. The author used only supramaximal stimulation with a duration of 0.1–0.4 ms.

Measurements

Peak to peak amplitude (μV) of the sensory nerve action potential (SNAP) was measured from the negative peak to the positive peak of the SNAP. In each hand of each volunteer, the amplitude of the median SNAP was also expressed as a percentage of the amplitude of the ulnar SNAP. Skin and room temperature data were not given. Median to ulnar amplitude ratio (Amp Rat) was determined by dividing the median digital sensory amplitude (stimulating at the wrist and recording to digit II) by the ulnar digital sensory amplitude (stimulating at the wrist and recording to digit V) as follows:
$$ \mathrm{Amplitude}\;\mathrm{ratio}\;\left(\%\right)=\frac{\mathrm{Digital}\kern0.24em \mathrm{sensory}\kern0.24em \mathrm{amplitude}\kern0.24em \mathrm{t}\mathrm{o}\kern0.24em \mathrm{t}\mathrm{he}\kern0.24em \mathrm{digit}\kern0.24em \mathrm{I}\mathrm{I},\kern0.24em \left(\mu \mathrm{V}\right)}{\mathrm{Digital}\kern0.24em \mathrm{sensory}\kern0.24em \mathrm{amplitude}\kern0.24em \mathrm{t}\mathrm{o}\kern0.24em \mathrm{t}\mathrm{he}\kern0.24em \mathrm{digit}\kern0.24em \mathrm{V},\kern0.24em \left(\mu \mathrm{V}\right)} $$
The author studied 100 normal hands from 50 healthy volunteers (Table 1) and 100 hands from 60 patients (Table 2) with the diagnosis of CTS (in 22 patients, the diagnosis was bilateral).
Table 1

Normal values [1]

Median nerve – peak to peak

Amplitude (μV) wrist–digit II

Mean ± SD

Range

All subjects

56.9 ± 21.5

20–128

Ulnar nerve – peak to peak

Amplitude (μV) wrist–digit V

Mean ± SD

Range

All subjects

47.5 ± 21.5

10–116

Median–ulnar nerves

Amplitude ratio (peak to peak)

Mean ± SD

Range

Limit of normal (−2 SD)

All subjects

1.254 ± 0.326

0.67–2.0

≥0.60

Median–ulnar nerves

Amplitude ratio (%)

<50

50–59

60–69

70–79

80–89

90–99

>100

All subjects (100 hands)

1

2

4

4

89

Table 2

Pathological values [1]

Median nerve – peak to peak

Amplitude (μV) wrist–digit II

Mean ± SD

Range

Group I – CTS with normal DSL

27.0 ± 15.5

2.4–70

Group II – peak DSL between 3.9 and 4.9 ms

22.7 ± 12.3

8–60

Group III – peak DSL ≥5.0 ms

15.2 ± 7.9

4–30

Group IV – absent median DSL

Ulnar nerve – peak to peak

Amplitude (μV) wrist–digit V

Mean ± SD

Range

Group I – CTS with normal DSL

32.9 ± 13.5

12–60

Group II – peak DSL between 3.9 and 4.9 ms

28.1 ± 15.4

10–76

Group III – peak DSL ≥5.0 ms

26.9 ± 12.2

10–50

Group IV – absent median DSL

19.4 ± 6.9

10–30

Median–ulnar nerves

Amplitude ratio (%)

<50

50–59

60–69

70–79

80–89

90–99

>100

Group I (17 hands)

3

2

1

3

1

7

Group II (31 hands)

4

5

4

4

4

10

Group III (14 hands)

5

4

5

Group IV (20 hands)

Comment

For Felsenthal [1], with reference to the normal values, the amplitude of the median SNAP usually equaled or exceeded the amplitude of the ulnar response (89 of 100 normal hands). The author compared the antidromic technique with the orthodromic technique described by Loong and Seah [3]. Since 1965, the difference in amplitude has been observed using orthodromic or antidromic techniques: the amplitudes of the evoked potential are typically smaller using the former technique. The amplitude of the observed response decreases with increasing distance from the source of the action potential. If one electrode is closer to the nerve than the other, its contribution will be increased so that mainly up-going or mainly down-going potentials may be recorded from the same nerve merely due to lateral displacement of one electrode. With the antidromic technique, the ring electrodes about digit II and digit V are probably equidistant from the digital nerves, but with surface electrodes, it is difficult to assure that both electrodes are equidistant from the nerve. The interelectrode distance is another factor that affects the amplitude of the SNAPs. The increase in amplitude secondary to increased interelectrode distance helps explain why the amplitude of the ulnar SNAP in some volunteers equals or exceeds that of the median SNAP (11 of 100 normal hands). Other factors like a smaller median contribution to the sensory innervation of the digit II or an excessive skin impedance may reduce the amplitude of the SNAP.

Comment

The criteria used by Felsenthal [1] for the diagnosis of carpal tunnel syndrome (CTS) included distal sensory latency (DSL) to onset of greater than 3.1 ms (onset latency was measured from the stimulus onset to the onset of the negative deflection of SNAP), DSL to peak of greater than 3.8 ms (peak latency was measured from the stimulus onset to the peak of the negative deflection of SNAP), greater than 0.4 ms difference between the median and ulnar DSL measured either to onset or peak, distal motor latency (DML) greater than 4.0 ms to onset, and greater than 1.0 ms difference between the median and ulnar DML in the same hand. The patients were subdivided into 4 groups. Group I was composed of all patients with normal median sensory latencies and either greater than 0.4 ms difference between the median and ulnar DSL or in two patients greater than 1.0 ms difference between the median and ulnar DML. Group II included all cases of CTS with DSL to peak of between 3.9 and 4.9 ms. Group III was composed of all patients with a latency to peak greater than 4.9 ms. Group IV included all cases with absent median DSL.

Bolton and Carter [4] studying 20 healthy subjects (10 men, age range 23–43 years, mean age 31 years; 10 women, age range 23–60 years, mean age 30 years) performed the antidromic sensory digit II and digit V recordings, in order to compare the amplitude of the evoked SNAPs with the sex of the subjects and the circumference of the wrist and of the finger studied. No fixed distance was used for the median and ulnar wrist stimulations, and the authors did not specify if both nerves were stimulated at the same distance (for men, the median nerve mean distance between the recording and stimulating electrodes was 15.6 cm, range 14.2–16.5 cm, and the ulnar nerve mean distance between the recording and the stimulating electrodes was 10.8 cm, range 11.8–13.5 cm; for women, the median nerve mean distance between the recording and the stimulating electrodes was 13.7 cm, range 11.8–15.1 cm, and the ulnar nerve mean distance between the recording and stimulating electrodes was 11.2 cm, range 9.9–12.5 cm). The authors did not perform a comparative conduction study between the median and ulnar amplitude SNAPs as Felsenthal’s method, but they investigated the role of the sex and the circumference of the wrist and of the finger on the amplitude of the evoked sensory responses. They used a DISA 14E11 constant voltage stimulating unit for supramaximal stimulation (0.1-ms duration), and TECA ring electrodes were placed at the level of the proximal crease of the digit for both median and ulnar nerves recordings. Skin temperature was recorded distally in the palm before each recording (the men mean temperature was 33.1 °C, range 31.0–34.8 °C; the women mean temperature was 32.5 °C, range 31.0–34.0 °C). Evoked action potentials were displayed on a Hewlett Packard 141B oscilloscope (frequency setting 10 Hz–2 kHz). The authors measured the negative peak amplitude because in the antidromic conduction, they frequently observed in sensory responses a distortion from muscle compound action potential. In the median and ulnar antidromic study to digit II and digit V, respectively, the authors observed a greater SNAP amplitudes in women than men, and they explained this difference by men having digits of greater circumference than women. They suggested taking into account this considerable diagnostic error when comparing the results in an individual patient with control data that included both sexes, especially when the axonal degeneration predominates and the maximum nerve conduction velocity remains near normal, the main effect being a reduction in the SNAP amplitude.

Monga and Laidlow [5] performed antidromic sensory conduction studies of both nerves using ring electrodes for recording and stimulating median and ulnar nerves at 14-cm fixed distance at the wrist using the same protocol by Felsenthal [1]. They studied 15 normal (Table 3) subjects (9 women and 6 men, mean age 40.3 years, age range 25–72 years) and 30 patients (21 women and 9 men, mean age 45.6 years, age range 21–83 years) with a history compatible with CTS. The authors used a TECA M model electromyograph equipment, and the sensory studies were performed in a room with a temperature of 23 °C. The skin temperature was not given.
Table 3

Normal values [5]

Median–ulnar nerves

Amplitude ratio (onset to peak)

Mean ± SD

Range

Limit of normal (−2 SD)

All subjects

1.29 ± 0.28

0.62–2.0

≥0.72

Jackson and Clifford [6] using a TECA model TD10A electromyograph (factory-set filters combination: 20 Hz–2 kHz for surface sensory recordings and 2 Hz–10 kHz for surface motor recordings) performed five different tests on 38 hands from 38 normal volunteers (Group A – 76 % women, mean age 42.2 ± 12.1 years, age range 21–69 years) and 123 patients having symptoms of CTS (Tables 4 and 5). After the electrodiagnostic examination that included both nerve conduction studies (NCS) and electromyography (EMG), the patients were subdivided into three groups: Group B (the mildest cases of median compression at the wrist, having normal findings on conventional NCS and EMG), Group C (more severe cases of median compression at the wrist, demonstrating abnormal conventional NCS but normal EMG), and Group D (most severe cases of median nerve compression at the wrist, demonstrating abnormal NCS and abnormal EMG). Group B was composed by 43 hands from 40 subjects (90 % women, mean age 43.5 ± 11.8 years, age range 21–66 years), Group C was composed by 55 hands from 53 subjects (75 % women, mean age 53.8 ± 12.8 years, age range 31–82 years), and Group D was composed by 33 hands from 30 subjects (83 % women, mean age 62.7 ± 17.3 years, age range 23–85 years).
Table 4

Normal values [6]

Median–ulnar nerves

Amplitude ratio (onset to peak)

Mean ± SD

Range

Limit of normal (−2 SD)

All subjects

1.21 ± 0.32

0.84–1.80

≥0.57

Table 5

Pathological values [6]

Median–ulnar nerves

Mean ± SD

Range

Limit of normal (−2 SD)

Distal latency difference (ms)

Group B

0.41 ± 0.36

0.0–2.90

≤0.35

Group C

1.72 ± 1.10

0.30–5.30

≤0.35

Group D

2.39 ± 1.77

0.40–6.30

≤0.35

Median–ulnar nerves

Amplitude ratio (onset to peak)

Mean ± SD

Range

Limit of normal (−2 SD)

Group B

1.11 ± 0.36

0.36–2.1

≥0.57

Group C

0.72 ± 0.38

0.0–2.2

≥0.57

Group D

0.34 ± 0.39

0.0–1.4

≥0.57

Aygül et al. [7] performed several median sensory and motor nerve conduction studies to evaluate prospectively the sensitivities of conventional and new electrophysiological techniques and to investigate their relationship with the body mass index (BMI). They performed electrophysiological studies with a Medelec TECA Premiere Plus vE05 electromyograph (20 Hz–3 kHz frequency filter). All tests were done in similar temperature conditions, and skin temperature at the hand was measured and maintained at or above 32 °C. They studied 60 hands (Table 6) of 30 healthy subjects (26 women and 4 men – BMI 26.5 ± 3.6, mean age 44.3 ± 8 years, age range 18–62 years) and 165 hands (Table 7) of 92 patients with clinical diagnosis of CTS (81 women and 11 men, mean age 45.7 ± 10.4 years, age range 18–72 years).
Table 6

Normal values [7]

Median–ulnar nerves

Amplitude ratio (onset to peak)

Mean ± SD

Range

All subjects

D2M–D5U SNAP ratio

1.21 ± 0.36

0.61–2.3

Table 7

Pathological values [7]

Median–ulnar nerves

Amplitude ratio (onset to peak)

Mean ± SD

Range

Limit of normal

All subjects

D2M–D5U SNAP ratio

0.80 ± 0.41

0.14–2.2

≥0.50

Comment

For Aygül et al. [7], the antidromic sensory median digit II–ulnar digit V SNAP ratio (D2M–D5U SNAP ratio) was abnormal in 45 hands (27 %), and it was the least sensitive test for the diagnosis of CTS. The authors observed that measurement of D2M–D5U SNAP ratio was abnormal in obese patients than in nonobese patients when compared to the BMI. Pathological waveform and values in a case of CTS are reported (Fig. 2).
Fig. 2

Antidromic sensory nerve action potentials (SNAPs) recorded to digit II (upper trace) and to digit V (lower trace), in very mild CTS – grade 1 by Bland’s CTS classification scale [8], stimulation of the median and ulnar nerves at the wrist

References

  1. 1.
    Felsenthal G (1978) Comparison of evoked potentials in same hand in normal subjects and patients with carpal tunnel syndrome. Am J Phys Med Rehabil 57:228–232Google Scholar
  2. 2.
    Felsenthal G (1977) Median and ulnar distal motor and sensory latencies in the same normal subjects. Arch Phys Med Rehabil 58:297–302PubMedGoogle Scholar
  3. 3.
    Loong SC, Seah CS (1971) Comparison of median and ulnar sensory nerve action potentials in the diagnosis of the carpal tunnel syndrome. J Neurol Neurosurg Psychiatry 34:750–754PubMedCentralPubMedCrossRefGoogle Scholar
  4. 4.
    Bolton CF, Carter KM (1980) Human sensory nerve compound action potential amplitude: variation with sex and finger circumference. J Neurol Neurosurg Psychiatry 43:925–928PubMedCentralPubMedCrossRefGoogle Scholar
  5. 5.
    Monga TN, Laidlow DM (1982) Carpal tunnel syndrome measurement of sensory potentials using ring and index fingers. Am J Phys Med Rehabil 61:123–129Google Scholar
  6. 6.
    Jackson DA, Clifford JC (1989) Electrodiagnosis of mild carpal tunnel syndrome. Arch Phys Med Rehabil 70:199–204PubMedGoogle Scholar
  7. 7.
    Aygül R, Ulvi H, Kotan D et al (2009) Sensitivities of conventional and new electrophysiological techniques in carpal tunnel syndrome and their relationship to body mass index. J Brachial Plex Peripher Nerve Inj 4:12PubMedCentralPubMedCrossRefGoogle Scholar
  8. 8.
    Bland JDP (2000) A neurophysiological grading scale for carpal tunnel syndrome. Muscle Nerve 23:1280–1283PubMedCrossRefGoogle Scholar

Copyright information

© Springer International Publishing Switzerland 2015

Authors and Affiliations

  • Giuliano Gentili
    • 1
  • Mario Di Napoli
    • 1
  1. 1.Neurological ServiceS. Camillo de’ Lellis General HospitalRietiItaly

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