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Year : 2013  |  Volume : 2  |  Issue : 3  |  Page : 194-201

Measurement of F wave components in a sample of healthy Iraqis: Normative data

1 Neurophysiology Unit, Gazi-Al Hariri Hospital, Medical City, Baghdad, Iraq
2 Department of Medical Physiology, College of Medicine, Al Nahrain University, Baghdad, Iraq
3 Department of Medical Physiology, College of Medicine, Baghdad University, Baghdad, Iraq

Date of Web Publication14-Feb-2014

Correspondence Address:
Farqad B Hamdan
Department of Medical Physiology, College of Medicine, Al-Nahrain University, Baghdad
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2278-0521.127065

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Background: F-waves are late responses often incorporated during performance of nerve conduction studies and have become an integral part of the electrodiagnostic examination. Objective: To study uncommonly measured F-wave parameters and to establish normative data in our country. Materials and Methods: The study included 126 healthy individuals aged between 18 to 55 years. F-waves minimum, mean and maximum latencies, persistence, F-amplitude, F-conduction velocity, chronodispersion, Tacheodispersion, and F-ratio were studied by surface electrodes from the abductor pollicis brevis, abductor digiti minimi, abductor hallucis, and extensor digitorum brevis by stimulating the median, ulnar, tibial, and common peroneal nerves, respectively. Results: Different F-wave parameters were presented in the manuscript. F-wave latencies were correlated with limb length and height. Conclusion: F-wave latencies correlate better to the limb length than the height. The use of F-wave latencies without such correlation may lead to an erroneous conclusion. F-wave parameters should be performed in routine nerve conduction studies.

Keywords: F-wave parameters, healthy subjects, Iraqi

How to cite this article:
Mohsen SS, Hamdan FB, Mohammed NH. Measurement of F wave components in a sample of healthy Iraqis: Normative data. Saudi J Health Sci 2013;2:194-201

How to cite this URL:
Mohsen SS, Hamdan FB, Mohammed NH. Measurement of F wave components in a sample of healthy Iraqis: Normative data. Saudi J Health Sci [serial online] 2013 [cited 2022 Jan 22];2:194-201. Available from: https://www.saudijhealthsci.org/text.asp?2013/2/3/194/127065

  Introduction Top

F wave was first described and designated as a late response by Magladery and McDougal. [1] They are produced by antidromic activation "backfiring" of motor neurons, [2] thus its measurement helps in assessing motor conduction along the entire length of the peripheral axons, including the most proximal segment. [3]

F waves are low-amplitude and ubiquitous responses inherently variable in amplitude, latency and configuration but occur grouped within a consistent range of latencies. [2] Because of their utilities and ease, its measurement has since gained popularity in evaluation of a variety of neurologic conditions as part of routine nerve conduction studies.

Measuring F wave in the extremities is frequently used to evaluate peripheral nerve function, [4],[5] demyelinating radiculoneuropathies, [6] radiculopathies, [5],[7],[8] neurogenic atrophy, [9] spinal stenosis and multilevel root injury, [10] increased central excitability states such as upper motor neuron, [11] and central nervous system lesions. [12]

The accuracy of defining normal values is improved by considering F wave variables such as F wave latency which is directly related to height, limb length and to a lesser degree age, [13],[14],[15],[16] minimum F wave latency (Fmin), [17] F wave mean latency (Fmean), [18] F wave maximum latency (Fmax), [19],[20] F wave conduction velocity (FwCV), [21] F wave amplitude (Fampl), [22] F wave persistence (Fp), [23],[24] F wave chronodispersion (Fchrono), [25] F wave tacheodispersion (Ftacheo), [25],[26] and F wave ratio (Fr). [27]

The intension of this study is to evaluate various parameters of F wave in a sample of healthy individuals in our region as well as to study effect of different physiological parameters on it; and to compare our results with the normative data published in literature.

  Materials and Methods Top

This study was conduct at the EMG unit, Gazi Al-Hariri Teaching Hospital and Al-Kadhimiya Teaching Hospital, Baghdad-Iraq during the period from January to July 2011.

One hundred and twenty six healthy individuals were selected from healthy volunteers between age group of 18 to 55 years after getting their informed written consent to participate in the study. They comprised 68 females with mean age of 36.49 ± 9.93 years and 58 males with a mean age of 32.82 ± 10.27 years. An approval from Institutional Ethics Committee was obtained.

All subjects were included in the study when they have normal neurological examination, normal laboratory findings regarding serum sugar, electrolytes and renal function. A standardized questionnaire was used to exclude those with a history of systemic or neuromuscular diseases. Moreover, those with a history of alcohol abuse or medications that might affect the results, those with a history of diabetes mellitus, hypothyroidism and systemic diseases were excluded.

F-waves were studied by micromed-8 channel EMG device, serial No. GH17H9NW315431B, model 171S, Italy. The room temperature was maintained relatively around 25 o C during the examination. The subjects were lying comfortably in the supine position and standardized technique was used to obtain and record action potentials for motor function measurements. [3]

The recording surface electrode was placed on abductor pollicis brevis for median, on abductor digiti minimi for ulnar nerve, on extensor digitorum brevis for peroneal and on abductor hallucis for tibial nerve. Reference electrode was placed 4 cm distally over first metacarpo-phalangeal joint for median, over fifth metacarpo-phalangeal joint for ulnar, over the proximal portion between third and fourth metatarso-phalangeal joint for peroneal and over proximal portion of first metatarso- phalangeal joint for tibial nerve. Stimulation of nerve was done at wrist for median and ulnar nerves and ankle for tibial and common peroneal nerves and the ground electrode was placed between stimulation and recording surface electrode.

The Fmin, Fmean and Fmax latencies, Fc, Fp, FwCV, and Fr values were determined for each nerve. Ftacheo was calculated by subtracting the minimum F wave conduction velocity (FWCV min) from maximum F wave conduction velocity (FWCV max).

Each nerve was stimulated supramaximally with stimulus frequency of 1 Hz, pulse duration of 0.2 ms and recordings were made with a sweep speed of 5 or 8 ms/cm and sensitivity of 0.2-0.5 mV/cm. For each nerve 10 successive stimuli were applied. [28]

The upper limb length was measured with a tape from the stimulus point to the C7 spinous process with the limb extended and abducted 90 o pronated for measurement of the ulnar nerve and supinated for the median nerve along the course of the nerve via the axilla and mid-clavicular point. For the lower limb, surface measurement followed the nerve course from the stimulus site to the T12 spinous process by way of the knee and greater trochanter of the femur.

Statistical package for the social science (SPSS), version 16 and Microsoft Office Excel 2007 were used for analyzing the data. ANOVA was used to analyze the relations among numeric data. The upper limit of the normal values was defined as mean plus two standard deviation (SD). Pearson's correlation coefficient was used to study correlation between two numeric variables. The probability limit (P value) of less than 0.05 was considered to be statistically significant.

  Results Top

The demographic features of 126 subjects enrolled in this study were presented in [Table 1]. Different F wave parameters for the upper and lower limbs are depicted in [Table 2].
Table 1: Demographic feature of the studied groups

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Table 2: Different F-wave parameters of the tested nerves

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Age showed significant effect on ulnar Flat mean, Fampl mim, and Fr max (P = <0.05). Moreover, age showed significant effect on median Flat mean (P = <0.05). Other F wave parameters not affected by age [Table 3].
Figure 3: Correlation between lower limb length and tibial F minimum amplitude

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The gender had significant effect on ulnar Flat min (P = <0.05). Furthermore, it has significant effect on peroneal Fr min, Fr mean Fr max (P = <0.01), and Fc (P = <0.05) but none to other F wave parameters.

A positive correlations was observed between upper limb length and each of ulnar Fr max (P = <0.05) and Fc (P = <0.01) but not with the rest of parameters. Moreover, a positive correlation (P = 0.01) was shown between body height and ulnar Fp [Table 4] and [Figure 1].
Figure 1: Correlation between upper limb length and body height with ulnar F wave chronodipersion, maximum ratio, and persistence

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Figure 4: Correlation between lower limb length and peroneal F minimum latency, minimum conduction velocity, minimum amplitude

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Upper limb length was not correlated with different median F wave parameters while body height was negatively correlated (P = <0.05) with Fr mean [Table 5] and [Figure 2].
Figure 2: Correlation between body height and median F mean ratio

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Figure 5: Correlation between body height and peroneal F minimum conduction velocity and minimum amplitude

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The lower limb length but not the body height was correlated (P = 0.001) with tibial Fampl min out of the total F wave parameters [Table 6] and [Figure 3].{Figure 3}
Table 6: Correlations between limb length and body height and different F-wave parameters of tibial nerve

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The lower limb length was positively correlated with peroneal Flat min, Fcv min (P = <0.01) and with Famp min (P = <0.0001). Moreover, body height was also positively correlated with Fcv min (P = <0.01) and Famp min (P = <0.05) as shown in [Table 7] and [Figure 4] and [Figure 5].{Figure 4}{Figure 5}
Table 7: Correlations between limb length and body height and different F wave parameters of the peroneal nerve

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  Discussion Top

Nerve conduction study is useful diagnostic technique in many disorders affecting the nerves function since a specific diagnosis of the peripheral nerves and muscles disorders cannot be established by clinical evaluation alone. [3] F wave study is a type of nerve conduction procedure often performed as an integral part of electrodiagnosis.

The median F minimum and maximum latency and F chronodispersion in present study is in keeping with published studies. [29],[30] F chronodispersion values were in agreement with the findings of Ghosh, [30] but not with the observation of Panayiotopoulos. [31]

The F mean CV harmonize with findings of Cornwall and Nelson, [32],[33] likewise, F minimum CV coexistent with the observation of Kohara et al., [33] but in contrast to others, [32] in addition, F ratio was not consistent with Ghosh [30] findings.

With regard to ulnar nerve, F minimum, mean, and maximum latency and F chronodispersion was similar to that found by other researchers. [12],[29],[30],[34] Yet, our observation concerning F chronodispersion was higher than the findings of Kohora et al. [33] Ulnar F persistence, tacheodispoersion, F ratio, and F minimum, mean, and maximum CV values of the present study were in accordance with that of Kimura [35] but different from findings of others. [12],[30] Ulnar F minimum, mean, and maximum amplitude were different from those recorded by Chroni et al., [12] but within the range reported by other authors. [33]

Considering the tibial nerve, the F minimum, mean and maximum latency and F chronodispersion, F tacheodispersion, F persistence, and F minimum CV values were nearly similar to those reported worldwide. [20],[29],[33],[34],[36] The F minimum CV was different from that noticed by Fisher et al. [37] On the contrary, F mean CV was lower than that demonstrated by Fisher et al., [37] but higher than the value reported by Ohgaki et al. [38] The latter group found higher F ratio values than in our study.

In our study, common peroneal F minimum, mean, and maximum latency values were coexistent with the observation of other researchers, [5],[34],[39],[40] but different from the findings of Alavian-Ghanavini and Haghpanah [20] and Hatamian and Imamhadi. [15]

Our observation of F mean amplitude, F chronodispersion and F tacheodispersion were in accordance with the values published worldwide [36],[39],[40],[41] but higher than those reported by others. [5],[20],42

F wave latency has been reported to increase with height by 0.2 ms/cm in the upper and 0.4 ms/cm in the lower limbs. [29] The present data confirm in apart the well-known correlation of F wave latencies to the limb length and height.

In assessing the F minimum latency of the ulnar nerve, for example, a value (30.7 msec) considered below an upper limit of normal for a tall (180cm) subject would clearly indicate an abnormal delay for a short individual (160cm). F chronodispersion of median ulnar, tibial nerves remains the same regardless of the change in limb length and height also shown by others. [28]

Any index based on height has an inherent limitation because limb lengths vary in different individuals with the same height. Thus, limb index correlating latency and limb length showed a narrower range of variability than the height index. Similarly, F conduction velocity, based on the limb length, provide a practical measure in all individuals, regardless of their height. [33],[35]

Most of F wave values in the current study were coexistent with the published researches but few showing a considerable difference which could be attributed to difference in the distance between the stimulating and recording electrodes, age of the subjects studied, number of the subjects examined, diversity of the methods and techniques (studies differ in maneuvering, setting, recording the electrical response, and equipment used) and ethnic group studied.

Some studies were done on Caucasian subjects, others on Asian; however, none of the studies done between Caucasian populations living in different geographical areas. At present it is difficult to attribute the differences to a single factor. On the other hand, the diversity could have resulted for variables that were not yet considered by workers such as body built and climatic dwelling conditions.

Although some have recommended that normal values be segregated by sex, as a surrogate measure for anatomical difference we feel it is more appropriate to incorporate age, height and finger circumference into regression models used to predict normal values because there is considerable overlap between the female and male distributions of these factors.

In conclusion, association between each F wave measure and independent variables known or hypothesized to affect F wave was found to be statistically significant, biologically plausible, and clinically important and the use of F wave latencies without such correction may lead to an erroneous conclusion.

  Acknowledgment Top

We would like to thank all members of Neurophysiology Unit in Al-Kadhimiya Teaching Hospital and Gazi Al-Hariri Hospital, Medical city for their great help and their cooperation. Our gratitude also extended to all subjects who participated in this work.

  References Top

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37.Ohgaki K, Nakano K, Shigeta H, Kitagawa Y, Nakamura N, Iwamoto K, et al. Ratio of motor nerve conduction velocity to F-wave conduction velocity in diabetic neuropathy. Diabetes Care 1998;21:615-8.  Back to cited text no. 37
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  [Figure 1], [Figure 2], [Table 3], [Table 4], [Table 5]

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]


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