4 predominance of ﬁnger ﬂexors over extensors in their upper limbs, which may cause a facilitated palmar grasp reﬂex on the aﬀected side(s) in spastic hemiplegia and quadriplegia. On the other hand, in children with CP of the athetoid type, the deviation of reciprocal innervation always leads to excess reciprocal inhibition. Any attempt at movement produces excessive relaxation of the antagonists, inducing an extreme range of movements [62]. Although the released control of the spinal reﬂex mechanism because of a lesion in the basal ganglia seems to be the most likely cause of facilitation of the plantar grasp reﬂex in these children, the excessive relaxation of toe extensors, in response to the toe ﬂexion at the moment of elicitation of the reﬂex, may be another factor causing an exaggerated response. Children with athetosis generally exhibit decreased tonus of ﬁnger muscles, especially of ﬂexors, which causes a weak grasp and the release of objects too easily [62]. The relative predominance of ﬁnger extensors over ﬂexors, in addition to the speciﬁc weakness of the ﬁnger muscles, may be a factor causing the diminished palmar grasp reﬂex in these children. In infants, the maturation of cortical connections over- rides the generators of primitive reﬂexes in the spinal cord and brain stem with age and eventually leads to the disappearance of the primitive reﬂexes and the emergence of righting and equilibrium reactions [34, 63]. The disap- pearance and emergence of these reﬂex mechanisms were demonstrated to be chronologically related to the attainment of motor milestones in normal children [24]. In children with MR, however, the process of evolution of these reﬂex mechanisms is prolonged, in accordance with the retardation of maturation in brain function, resulting in retention of primitive reﬂexes and the delayed attainment of motor milestones [24, 29, 34, 64]. 3. The Moro Reﬂex 3.1. Elicitation. In his original method, Moro [9] elicited the reﬂex by hitting the pillow on either side of an infant’s head with the hands. Later a variety of methods for eliciting the reﬂex were devised including hitting on the table surface, warm or cold application to the chest or stomach, and a tap on the abdomen [10, 11]. Nowadays, however, the head drop method is the most common, because a slight drop of the infant’s head relative to the body axis in the supine position is generally accepted as the most eﬀective technique for eliciting the reﬂex [10, 11, 19]. For elicitation in this method, the infant is held suspended in a symmetrical supine position with one of the examiner’s hands behind the chest and the other supporting the head, and the head being held in a midline position and then dropped back a few cm. It is important to ensure that both the subject’s hands are open at the moment of elicitation of the reﬂex so as not to provoke an asymmetrical response [14]. Infants should be tested while they are awake, but not crying [18]. The drop of the baby method is an alternative one for eliciting the reﬂex: the infant is suspended horizontally, as in the head drop method, and then the examiner lowers his or her hands rapidly about 10 to 20 cm and brings them to an abrupt halt. There is no dorsiﬂexion of the neck with International Journal of Pediatrics this technique [18]. On the other hand, Lesny´ [65] reported that a nociceptive stimulus applied to the infant’s skin and subcutaneous tissue of the epigastrium by pinching was eﬀective for eliciting the reﬂex. The initial phase of the response comprises abduction of the upper limbs at the shoulders and extension of the forearms at the elbows, with slight extension of the spine and retraction of the head. The forearms are supinated and the digits extended, except for the semiﬂexed index ﬁngers and thumbs, forming the shape of a “C”. There is sometimes a slight tremor or clonus-like rhythmic movements of the limbs. Subsequently the arms adduct at the shoulders and the forearms ﬂex at the elbows: the upper limbs describe an arc-like movement, bringing the hands in front of the body, which ﬁnally return to the original position [10, 11, 18]. The responses of the lower limbs are usually eliminated from the evaluation, because they show wide variability among the normal population [11, 19, 20]. With this reﬂex, habituation develops only on an experimental basis with intensively repetitive trials, that is, not in the clinical setting [17, 66]. No signiﬁcant diﬀerence in the response has been reported at birth or through the ﬁrst 5 months of age between the term cephalic-presenting and breech-presenting infant groups [67]. 3.2. Clinical Signiﬁcance 3.2.1. Responses in Normal Infants. The study of the Moro reﬂex in normal term infants has been undertaken by many authors. The results obtained with the head drop method are well consistent. The reﬂex can be elicited in all infants during the ﬁrst 12 weeks of age. After the neonatal period, however, the response becomes increasingly less typical with age, eventually consisting only of abduction and extension of the upper limbs. Beyond 12 weeks of age, the proportion of infants exhibiting a negative response rapidly increases, reaching about 80% at 20 weeks of age [25]. The reﬂex usually disappears by 6 months of age [11, 31, 68–70]. Several authors compared the Moro reﬂex in preterm infants tested at 40 weeks PCA or at 4 months of corrected age with that in term infants. Although none of the studies conﬁrmed the outcome in the subjects, there is a general agreement as to the similarity in the response between the two groups, especially when only infants with no or low perinatal risk factors are compared [1, 71–75]. 3.2.2. Abnormal Responses. Based on the ﬁndings in normal infants, the absence or diminution of the Moro reﬂex within 2 to 3 months of age and the persistence of the response beyond 6 months of age can be regarded as abnormal. The absence of the response during the neonatal period and early infancy is of especial clinical signiﬁcance and may indicate a compromised condition or disorder including birth injury, severe birth asphyxia, intracranial hemorrhage, infection, brain malformation, general muscular weakness of any cause, and CP of the spastic type [10, 31, 69, 76, 77]. On the other hand, a hyperactive response of the reﬂex is a common feature of neonatal withdrawal from maternal drug