The palmomental reflex was studied in 611 normal subjects and 184 mentally retarded subjects (including 48 patients with Down’s syndrome). The reflex was present in 66 per cent of normal children under the age of three years but it was elicited in only 9 per cent of normal adults. In retarded children under the age of three years it was present in 81 per cent, but it did not sharply decline thereafter, as in normal subjects, and was still present in 44 per cent of the mentally retarded adults. The highest frequency was found in adults with Down’s syndrome.
The palmo-mental reflex appears to be a primitive reflex which persists if there is developmental delay or which may re-emerge in acquired brain disease and it is suggested that the reflex is a useful clinical sign.
