Affiliations: [a] Departments of Neurology, Faculty of Medicine, Ataturk University, Erzurum, Turkey | [b] Departments of Neurology, Faculty of Medicine, Sakarya University, Sakarya, Turkey | [c] Neurology Specialist, Medicana Hospital, Konya, Turkey
Correspondence:
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Address for correspondence: Dilcan Kotan, Departments of Neurology, Faculty of Medicine, Sakarya University, Sakarya, Turkey. E-mail: dilcankotan@yahoo.com
Note: [1] Presented in part at the 13th European Congress of Clinical Neurophysiology 4–8 May 2008, Istanbul, Turkey.
Abstract: Purpose: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). Method: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 (FCD), 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 FCD 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 FCD 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. Conclusion: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.
Keywords: Carpal Tunnel Syndrome, median nerve F waves, nerve conduction studies, subtypes
