Moro Reflex

Original Editor - Muskan Rastogi Top Contributors - Muskan Rastogi, Kim Jackson, Cindy John-Chu and Ahmed M Diab

Introduction

It was first described by Ernst Moro in 1918 and is a primitive infantile reflex. It is easily confused with a startle pattern or reflex. This reflex is said to be of labyrinthine origin.

Position

Head Drop Method: Supine position. Suspend the baby horizontally, in a symmetrical supine position such that the therapist's one hand behind the chest and the other supports the head. The infant's head should be in the midline position.

It is important to guarantee that both the infant's hands are open at the moment of elicitation of the reflex so as not to produce any asymmetrical response. Also, ensure that the baby is awake and not crying during the examination.

Baby Drop Method: Same as the head drop method.

Stimulus

Head Drop Method: Dropping the head of the baby by a few centimetres.

Baby Drop Method: The therapist lowers their hands rapidly about 10 to 20 cm and brings them to an abrupt halt.

Subcutaneous Stimulus: Painful stimulus to the subcutaneous tissue of the epigastrium. ( considered to be a more sensitive technique)

Response

Normal Response

Initial Phase: Abduction of the upper extremities and extension of the arms. The fingers extend, and there is a slight extension of the neck and spine.

After Phase: Arms adduct and the hands come to the front of the body before returning to the infant's side.

Abnormal Response

The disintegration of the reflex within 2 to 3 months of age.

Persistence of the response beyond 6 months of age.

Asymmetrical response.

Duration

This reflex can be stimulated in all neonates during the first 12 weeks of age and disintegrates by 6 months of age.

The examiner holds the infant in the supine position and drops the head slowly downwards. Abduction of upper extremities followed by extension of arms with a fingers extension is seen.

Neural Mechanism

This reflex is primarily elicited with the help of vestibular nuclei. It is mediated by the brainstem and therefore its centre seems to be in the lower region of the pons to the medulla. The efferent pathways of the response seem to originate in the vestibulospinal and/or reticulospinal neurons and the reflex movement is generated by the subcortical structures without cortical participation.

The Difference between Moro and Startle Reflex

The startle reflex, the response to a sudden stimulus, is one of the defensive reactions and consists essentially of flexion movements. It differs from the Moro response which is characterized by extension.

The startle reaction is induced by an auditory stimulus which shows clear habituation in premature infants, whereas the Moro reflex does not

The startle reaction can not be elicited in anencephalic newborns, while the Moro reflex was always elicited in these infants.

Clinical Significance

• The absence or premature disappearance of the Moro reflex can result from a birth injury, severe asphyxia during the birthing process, intracranial haemorrhage, infection, brain malformation, and general muscular weakness of any cause, and cerebral palsy of the spastic type.
• Asymmetrical Moro is said to be caused due to a local injury.
• Damage to a peripheral nerve, cervical cord, or a fracture of the clavicle are common causes which lead to an asymmetric Moro Reflex and causes inhibition of the reflex on the affected side.
• Prolonged retention of the reflex is said to be a sign of spastic cerebral palsy.
• A study showed a clear association between retained primitive reflexes and delay in motor development in very low birth weight infants.
• A hyperactive response of the reflex is a common feature of neonatal withdrawal from maternal drug abuse including volatile substances, heroin, and opioids and may also be detected in infants with a severe bilateral intrauterine disturbance such as hydranencephaly.
• ADHD is linked to persistent Moro Reflex in school children.