Moro reflex: Difference between revisions

{{Short description|Neurologic importance}}[[File:Moro reflex in four-day-old infant.ogv|thumbtime=6|thumb|The Moro reflex in a four-day-old infant: 1) the reflex is initiated by pulling the infant up from the floor and then releasing him; 2) he spreads his arms; 3) he pulls his arms in; 4) he cries (''10 seconds'')]]

The '''Moro reflex''' is an [[infantile reflex]] that develops between 25-3028 and 32 weeks of gestation and disappears betweenat 3-63–6 months of age. It is a response to a sudden loss of support and involves three distinct components:<ref name="Edwards 2019">{{Citation|lastlast1=Edwards|firstfirst1=Christopher W.|title=Moro Reflex|date=2019|url=http://www.ncbi.nlm.nih.gov/books/NBK542173/|work=StatPearls|publisher=StatPearls Publishing|pmid=31194330|access-date=2019-08-06|last2=Al Khalili|first2=Yasir}}</ref>

It is distinct from the [[Startle reaction|startle reflexresponse]].<ref>{{cite book |last=Fletcher |first=Mary Ann |title=Physical Diagnosis in Neonatology |year=1998 |publisher=Lippincott-Raven |location=Philadelphia |isbn=978-0397513864 |url=https://books.google.com/books?id=2chdTE4SHE8C&lpg=PA472&vqq=moro%20reflex&pg=PA472#v=snippet&q=moro%20reflex&f=false |accessdateaccess-date=7 February 2013 |page=472}}</ref> Unlike the startle reflexresponse, the Moro reflex does not decrease with repeated stimulation.<ref name=":0">{{Cite web|url=https://www.hindawi.com/journals/ijpedi/2012/191562/journal |title=The Grasp Reflex and Moro Reflex in Infants: Hierarchy of Primitive Reflex Responses |lastlast1=Suzuki |firstfirst1=Yasuhiro |last2=Toribe |first2=Yasuhisa |date=June 11, 2012 |websitejournal=International Journal of Pediatrics |volume=2012 |pages=191562 |doi=10.1155/2012/191562 |pmc=3384944 |pmid=22778756|access-date=2019-08-01 |last3=Futagi |first3=Yasuyuki |doi-access=free}}</ref> The primary significance of the Moro reflex is in evaluating integration of the [[central nervous system]].<ref name=":0"/>

== Eliciting the Moro Reflexreflex ==

==Clinical Significancesignificance ==

The Moro reflex may be observed in incomplete form in [[premature birth]] after the 25th week of [[gestation]], and is usually present in complete form by week 30 ([[third trimester]]).<ref>{{Citation|last name="Edwards|first=Christopher W.|title=Moro Reflex|date=2019|url=http:"//www.ncbi.nlm.nih.gov/books/NBK542173/|work=StatPearls|publisher=StatPearls Publishing|pmid=31194330|access-date=2019-08-06|last2=Al Khalili|first2=Yasir}}</ref> 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.<ref name=":0" /> Furthermore, absence during the neonatal period may warrant assessment for the possibility of developmental complications such as birth injury or interference with brain formation.<ref name=":0" /> Asymmetry of the Moro reflex is especially useful to note, as it is almost always a feature of root, [[plexus]], or nerve disease.<ref>{{Cite book|url=http://worldcat.org/oclc/878742566|title=Neurology of the newborn|last=Volpe|first=Joseph J.|journal=Major Problems in Clinical Pediatrics|date=2008|volume=22|publisher=Saunders/Elsevier|year=|isbn=9781416039952|locationpages=1–648|pagespmid=7022034|oclc=878742566}}</ref>

The Moro reflex is impaired or absent in infants with [[kernicterus]].<ref>{{Cite web|url=https://rarediseases.org/rare-diseases/kernicterus/|title=Kernicterus|website=NORD (National Organization for Rare Disorders)|language=en-US|access-date=2019-08-06}}</ref>

An exaggerated Moro reflex can be seen in infants with severalsevere brain damage that occurred in-utero, including [[microcephaly]] and [[Hydranencephaly|hydrancephalyhydranencephaly]].<ref>{{Cite web|url=https://www.sciencedirect.com/topics/medicine-and-dentistry/moro-reflex|title=Moro Reflex - an overview|last=Multiple authors|first=|date=|website=ScienceDirect Topics|archive-url=|archive-date=|dead-url=|access-date=2019-08-01}}</ref> Exaggeration of the Moro reflex, either due to low threshold or excessive clutching, often occurs in newborns with moderate hypoxic-ischemic encephalopathy.<ref>{{Citation|title=179 Neonatal Neurology|date=2011|url=http://www.springerreference.com/index/doi/10.1007/SpringerReference_226504|work=SpringerReference|publisher=Springer-Verlag|language=en|doi=10.1007/springerreference_226504|access-date=2019-08-05}}</ref> The Moro reflex is also exaggerated in infants withdrawing from narcotics.<ref>{{Cite journal|lastlast1=Chasnoff|firstfirst1=Ira J.|last2=Burns|first2=William J.|date=1984|title=The Moro Reaction: A Scoring System for Neonatal Narcotic Withdrawal|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-8749.1984.tb04475.x|journal=Developmental Medicine & Child Neurology|volume=26|issue=4|pages=484–489|doi=10.1111/j.1469-8749.1984.tb04475.x|pmid=6479468|s2cid=36440317|issn=1469-8749}}</ref>

Persistence of the Moro reflex beyond 6 months of age is noted only in infants with severe neurological defects, including [[cerebral palsy]].<ref>{{cite book |last1=Samuels |first1=Martin A. |authorlink1author-link1=Martin A. Samuels |last2=Ropper |first2=Allan H. |title=Adams and Victor's Principles of Neurology |year=2009 |publisher=McGraw-Hill Medical |location=New York |isbn=9780071499927 |chapter-url=http://www.mhprofessional.com/product.php?isbn=007149992X |edition=9th |accessdateaccess-date=7 February 2013 |chapter=Normal Development and Deviations in Development of the Nervous System}}</ref><ref>{{Cite journal|lastlast1=Agarwal|firstfirst1=Anil|last2=Verma|first2=Indreshwar|date=December 2012-12|title=Cerebral palsy in children: An overview|url=https://linkinghub.elsevier.com/retrieve/pii/S0976566212000446|journal=Journal of Clinical Orthopaedics and Trauma|language=en|volume=3|issue=2|pages=77–81|doi=10.1016/j.jcot.2012.09.001|pmc=PMC38728053872805|pmid=26403442}}</ref>

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).<ref name=":1" /> 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 moroMoro reflex has been used to detect early neurological problems in infants.<ref name=":1">{{Cite journal|lastlast1=Weirich|firstfirst1=Angela|last2=Hoffmann|first2=Georg F.|s2cid=27343540|date=2005-10-01|title=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|url=https://doi.org/10.1007/s00431-005-1703-2|journal=European Journal of Pediatrics|volume=164|issue=10|pages=599–606|doi=10.1007/s00431-005-1703-2|pmid=15931526|issn=1432-1076}}</ref> Absence or prolonged retention of Moro reflex can be signs that the infants need neurological attention.<ref>{{Citation|lastlast1=Edwards|firstfirst1=Christopher W.|title=Moro Reflex|date=2019|url=http://www.ncbi.nlm.nih.gov/books/NBK542173/|work=StatPearls|publisher=StatPearls Publishing|pmid=31194330|access-date=2019-08-01|last2=Al Khalili|first2=Yasir}}</ref>

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.<ref name=berk>{{cite book |last=Berk |first=Laura E. |title=Child Development |year=2009 |publisher=Pearson |location=Boston |isbn=978-0-205-61559-9 |url=httphttps://wwwarchive.mypearsonstore.comorg/bookstoredetails/child-development-9780205615599childdevelopment02berk |edition=8th |accessdateaccess-date=7 February 2013 |url-access=registration }}</ref> The Moro reflex might also be an alarm signal from the baby who is about to lose support, and the spread arms provide extremities for where to be grabbed by its handler to prevent a fall. <ref>{{cite book |last=Altin |first=Simon Peter |author-link= |date=2024 |title=Paleothinking: Going Back in Time to Understand Human Nature |url= |location= |publisher=KDP |page=67 |isbn=979-8875858369}}</ref>