The relationship of median nerve F-wave parameters with severity and subtypes of carpal tunnel syndrome.
OBJECTIVE
F-wave analysis may help affirm or disprove a compression neuropathy. In this study we have analysed the effects of focal median nerve injury on F wave in Carpal Tunnel Syndrome (CTS).


METHODS
We studied 57 patients (100 hands) with clinical and electrophysiological CTS and 31 (62 hands) healthy subjects. Median nerve F-waves were evaluated following 10 supramaximal stimuli and recording from abductor pollicis brevis muscles. Minimum, maximum, and mean F-wave latencies, frequency of the F wave (Fp), chronodispersion (F<formula>_{CD}</formula>), mean F/M amplitude ratios (mF/M-amp) and F-wave conduction velocity (FwCV) were evaluated.


RESULTS
The CTS patients showed prolonged F-wave latencies, decreased Fp, and an increase of the F<formula>_{CD}</formula> as compared with normative values. Absent F wave was presented in 8 of 34 hands (23.5%) with severe CTS patients. In the severe group, the FwCV was significantly slower (p< 0.001) and the mF/M-amp was significantly higher (p< 0.001) than that of mild and moderate groups, respectively. Also, the mF/M-amp was significantly greater and Fp was lower in the axonal type than in the demyelinating type. The F<formula>_{CD}</formula> was not different among groups. A strong positive correlations between mMDL with Fmin (r=0.81, p< 0.000), Fmean (r=0.80, p< 0.000) and Fmax (r=0.71, p< 0.000) were revealed.


CONCLUSIONS
Results support the differing effects of demyelinating and axonal injury on F-waves and suggest that the mF/M-amp ratio and FwCV, which is influenced by neuronal damages in the distal segment of the median nerve, is useful in the discrimination of CTS severity.
Departments of Neurology, Faculty of Medicine, Ataturk University, Erzurum, Turkey.
Recep
R
Aygül
Departments of Neurology, Faculty of Medicine, Sakarya University, Sakarya, Turkey.
Dilcan
D
Kotan
Departments of Neurology, Faculty of Medicine, Ataturk University, Erzurum, Turkey.
Hızır
H
Ulvi
Departments of Neurology, Faculty of Medicine, Ataturk University, Erzurum, Turkey.
Mutlu
M
Kuyucu
Departments of Neurology, Faculty of Medicine, Ataturk University, Erzurum, Turkey.
Gökhan
G
Özdemir
Departments of Neurology, Faculty of Medicine, Ataturk University, Erzurum, Turkey.
Ayfer
A
Ertekin
Neurology Specialist, Medicana Hospital, Konya, Turkey.
Faruk Ömer
FÖ
Odabaş
D000328:Adult; D002349:Carpal Tunnel Syndrome / Q000175:diagnosis* / Q000503:physiopathology; D004568:Electrodiagnosis; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000503:physiopathology*; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology*; D012720:Severity of Illness Index
Carpal Tunnel Syndrome; median nerve F waves; nerve conduction studies; subtypes