The lateral tongue reflex in human neonates.

We undertook an investigation of the lateral tongue reflex to determine whether reflex sensitivity was systematically related to selected perinatal factors. The subjects were 24 male and 27 female newborns with a mean age of 28.9 hr. (SD = 16.8, range 5--72 hr.). The lateral tongue reflex was elicited by applying tactile stimulation of varying intensity to the lateral edge of the tongue approximately 1 cm off midline. Eight different stimuli from the Semmes-Weinstein esthesiometer were used; forces ranged from 68 mg to 3.6 gm. A total of 32 stimulations were given in two repetitions of 16 each (8 on the right side and 8 on the left side). The mean number of positive responses was 19.9 (SD = 3.2, range 13--25), with a 5% response at the lowest level of stimulation and a 100% response at the highest level. There were not differences in total number of positive responses or thresholds on the right and left sides, or in Repetitions I and II. There were no differences between males and females, vaginally and caesarian delivered infants, or resuscitated and non-resuscitated infants. No systematic differences were observed as a function of length of labor, obstetric medications, postnatal age at time of testing, Apgar scores, birth weight, or gestational age. The results suggest that the lateral tongue reflex is a stable and reproducible response that could be used to measure oral sensation, both in normal neonates and in subjects with various anatomical and/or neurosensory deficits.