The Moro reflex is an infantile reflex normally presents starting from 32 weeks gestation and disappears by 3 or 6 months of age as a response to a sudden loss of support, when the infant feels as if it is falling. It involves three distinct components:
The primary significance of the Moro reflex is in evaluating integration of the central nervous system. It is distinct from the startle reflex.[1] Unlike the startle reflex, the Moro reflex does not decrease with repeated stimulation.[2]
Eliciting the Moro Reflex
Ernst Moro elicited the Moro reflex by slapping the pillow on both sides of the infant's head. Other methods have been used since then, including rapidly lowering the infant (while supported) to a sudden stop and pinching the skin of the abdomen. Today, the most common method is the head drop, where the infant is supported in both hands and tilted suddenly so the head is a few centimeters lower than the level of the body.[2]
Clinical Significance
The Moro reflex may be observed in incomplete form in premature birth after the 28th week of gestation, and is usually present in complete form by week 34 (third trimester)[citation needed]. Absence or asymmetry of either abduction or adduction by 2 to 3 months age can be regarded as abnormal, as can persistence of the reflex in infants older than 6 months.[2] Furthermore, absence during the neonatal period may warrant assessment for the possibility of developmental complications such as birth injury or interference with brain formation.[2] Asymmetry of the Moro reflex is especially useful to note, as it is almost always a feature of root, plexus, or nerve disease.[3]
Absence of the Moro reflex is normally indicative of a disorder of the motor system or a generalized disturbance of the central nervous system. The Moro reflex is impaired in the early stage of kernicterus and it is absent in the late stage of kernicterus.
An exaggerated Moro reflex can be seen in infants with several brain damage that occurred in-utero, including microcephaly and hydrancephaly.[4] Exaggeration of the Moro reflex, either due to low threshold or excessive clutching, often occurs in newborns with moderate hypoxic-ischemic encephalopathy.[5] The Moro reflex is also exaggerated in infants withdrawing from narcotics.[6]
Persistence of the Moro response beyond 6 months of age is noted only in infants with severe neurological defects.[7] In individuals with cerebral palsy, persistence and exacerbation of this reflex is common.
History
The Moro reflex was first described in western medicine by Austrian pediatrician Ernst Moro (1874–1951) in 1918. Moro referred to it as the Umklammerungsreflex (embracing reflex).[8] In this publication, he stated: "When a young infant is placed on the examination table and one taps with hands on both sides of the pillow, there follows a rapid symmetrical extending abduction of both extremities, which approach each other in adduction immediately thereafter". According to him, this reflex should disappear after the infant's first 3–6 months of life. Since then, the moro reflex has been used to detect early neurological problems in infants.[8] Absence or prolonged retention of Moro reflex can be signs that the infants need neurological attention.[9]
Function
The Moro reflex may be a survival instinct to help the infant cling to its mother. If the infant lost its balance, the reflex caused the infant to embrace its mother and regain its hold on the mother’s body.[10]
References
- ^ Fletcher, Mary Ann (1998). Physical Diagnosis in Neonatology. Philadelphia: Lippincott-Raven. p. 472. ISBN 978-0397513864. Retrieved 7 February 2013.
- ^ a b c d Suzuki, Yasuhiro; Toribe, Yasuhisa; Futagi, Yasuyuki (2012). "The Grasp Reflex and Moro Reflex in Infants: Hierarchy of Primitive Reflex Responses". International Journal of Pediatrics. doi:10.1155/2012/191562. PMC 3384944. PMID 22778756. Retrieved 2019-08-01.
{{cite web}}: CS1 maint: unflagged free DOI (link) - ^ Volpe, Joseph J. (2008). Neurology of the newborn. Saunders/Elsevier. ISBN 9781416039952. OCLC 878742566.
- ^ Multiple authors. "Moro Reflex - an overview". ScienceDirect Topics. Retrieved 2019-08-01.
{{cite web}}: Cite has empty unknown parameter:|dead-url=(help) - ^ "179 Neonatal Neurology", SpringerReference, Springer-Verlag, 2011, doi:10.1007/springerreference_226504, retrieved 2019-08-05
- ^ Chasnoff, Ira J.; Burns, William J. (1984). "The Moro Reaction: A Scoring System for Neonatal Narcotic Withdrawal". Developmental Medicine & Child Neurology. 26 (4): 484–489. doi:10.1111/j.1469-8749.1984.tb04475.x. ISSN 1469-8749.
- ^ Samuels, Martin A.; Ropper, Allan H. (2009). "Normal Development and Deviations in Development of the Nervous System". Adams and Victor's Principles of Neurology (9th ed.). New York: McGraw-Hill Medical. ISBN 9780071499927. Retrieved 7 February 2013.
- ^ a b Weirich, Angela; Hoffmann, Georg F. (2005-10-01). "Ernst Moro (1874–1951)—A great pediatric career started at the rise of university-based pediatric research but was curtailed in the shadows of Nazi laws". European Journal of Pediatrics. 164 (10): 599–606. doi:10.1007/s00431-005-1703-2. ISSN 1432-1076.
- ^ Edwards, Christopher W.; Al Khalili, Yasir (2019), "Moro Reflex", StatPearls, StatPearls Publishing, PMID 31194330, retrieved 2019-08-01
- ^ Berk, Laura E. (2009). Child Development (8th ed.). Boston: Pearson. ISBN 978-0-205-61559-9. Retrieved 7 February 2013.