Latency, Duration and Persistence of Fersen Reflex in Infants

Abstract

The latency and duration of Fersen reflex were measured in 24 normal full-term infants from 0 to 10 months of age, 54 normal preterm infants from 0 to 5 months of corrected age, and 17 children with developmental disabilities aged 0 month to 3 years including 5 cases with disturbance of central coordination, 8 cases with cerebral palsy and 4 cases with severe mental and motor disabilities.
To perform the Fersen reflex study, a pick-up electrode was placed over the belly of the rectus femoris. The infant's heel was hit with a patella hammer which triggered the sweep of the electromyography (EMG) at the same time. The latency and duration of the muscle action potential which occurred with the extension of the infant's lower extremity were measured by EMG.
The latency of Fersen reflex in normal full term infants was constant during the first 10 months. The mean value was approximately 10 msec and similar to that of normal preterm infants, which was also constant during the first 5 months. Such short latency as that of H reflex in infancy suggested that this reflex was monosynaptic. With respect to the latency of Fersen reflex, there was no difference between normal infants and children with developmental disabilities. However, the duration of Fersen reflex in children with cerebral palsy was significantly prolonged that that of normal infants. In addition, marked persistence of Fersen reflex over the first year was observed in children with cerebral palsy, while this reflex tended to diminish after 4 months of age in normal infants.
With these findings, it seems difficult to distinguish infants with developmental disabilities from normal infants by comparing the latency of Fersen reflex. In Fersen reflex, the intensity of the response and the persistence should be evaluated than the latency.