F-ratio, a surrogate marker of carpal tunnel syndrome

To explore the correlation of F-ratio and F-wave minimal latency (FWML) in carpal tunnel syndrome (CTS).

This retrospective study was conducted from January 2006 to January 2007 at the clinical physiology lab, King Abdul-Aziz University Hospital, Riyadh, Saudi Arabia. Motor and sensory nerve conduction studies, FMW latencies of median and ulnar nerves, and F-ratio were carried out in 54 CTS patients and 30 controls.

Out of 54 CTS patients, there were 14 were males (26%), and 40 females (74%), CTS was bilateral in 32 (59%), and unilateral in 22 (41%) patients. Fifty-one patients (94.4%) had involvement of the right hand, 28 patients (51.8%) had dyslipidemia and 20 patients (37%) had hypertension. The FWML (ms) in the right median nerve was 25.46+/-2.2, and 25.79+/-1.7 in the right ulnar nerve in the control group (p=0.5224), while it was 29.1+/-3.35 in the right median nerve and 26.46+/-4.35 in the right ulnar nerve in patients with CTS (p=0.0008). A similar statistically significant increase in the median nerve latency was observed in the left hand. A statistically significant reduction in the F-ratio was found consistently in all patients with CTS in both the hands (p=0.0001).

The present study reveals prolongation of FWML in the median nerve, and a statistically significant reduction of F-ratio in all CTS patients. A significant inverse correlation was found between FWML and F-ratio in CTS patients. Both FWML and F-ratio support the diagnosis of CTS.