Effect of Menstrual Cycle in Long Latency Reflex of Abductor Pollicis Brevis Among Healthy Female Volunteers.

ABSTRACT

Background: Long Latency Reflex (LLR) is one of the late responses occurring after H reflex from a mixed nerve by submaximal stimulation. LLR has been found to be absent in patients with multiple sclerosis, spastic patients and in Huntington’s disease. A change in body temperature affects conduction velocity. It is a known fact that there is a change in body temperature during menstrual cycle. However, no studies are available to indicate changes in latency of LLR during the menstrual cycle. Aim: To determine the effect of menstrual cycle on Long Latency Reflex of Abductor Pollicis Brevis among healthy female volunteers. Material and Methods: A cross sectional study was carried out in 30 healthy female volunteers aged 20-30 yrs. The study was conducted between 9.00 a.m.-11.00 a.m using Digital Nerve Conduction/EMG/EP machine (Recorders Medicare system, India) in a laboratory maintained at 22º±3ºC. LLR was recorded during early follicular and mid-luteal phases by stimulation of median nerve while abducting the thumb and recording the EMG response of Abductor Pollicis Brevis. Body temperature was recorded. Latency of LLR obtained during two phases of menstrual cycle was compared. Result: The mean value of latency for LLR was 45.45±2.95 ms (mean±SD) in the mid luteal phase. It was significantly (Wilcoxon test, p<0.001) shorter than the value in the early follicular phase 47.10±2.51ms (mean±SD). This is possibly due to the higher body temperature in the mid luteal phase. Conclusion: Long Latency Reflex was found to be affected during the phases of the menstrual cycle in healthy female volunteers.