More than a Moro: The case of a twitching infant


The case reads: 6-week-old female with twitching episodes. It helps to educate yourself regarding the Moro reflex.

Key Points


You are nearing the end of a busy emergency department (ED) shift when you pick up your last patient chart of the night and read: "6-week-old female with twitching episodes." You peek into the room and see concerned young parents attending to their calm infant. Anticipating that these new parents will simply need education regarding the Moro reflex, you approach the room confident that your night will end uneventfully.

The patient is a 6-week-old, full-term girl with an uncomplicated prenatal and perinatal history. Her parents report that they awoke last evening to a brief choking sound coming from their daughter's bassinet. They found the baby lying on her back with her neck extended, eyes deviated upwards, and legs held straight. All 4 of her extremities were twitching rhythmically.

She had 3 more similar episodes over the next 8 hours. Her fourth episode occurred the next morning in the gynecologist's office at her mother's 6-week postpartum appointment. A nurse witnessed the event and directed the parents to the ED for further evaluation.

Before last evening, her parents had not witnessed a similar event. They deny that the child has had a fever or any preceding illness.

Except for the time period immediately after each event, she has been behaving and feeding normally. She frequently has small volume emesis after feeds that are not associated with back arching or irritability.

Physical findings

This story is more concerning than you had anticipated; it certainly does not sound as though these events can be attributed to infantile reflexes.

You proceed with the exam. The child's vital signs include an axillary temperature of 36.3°C, heart rate of 156 beats per minute, respiratory rate of 54 breaths per minute, and oxygen saturation of 100%. Her weight is 5.5 kg, 1.6 kg more than her birth weight and at the 96th percentile. Her length is at the 64th percentile; her head circumference is at the 83rd percentile.

She is resting comfortably in her mother's arms, but she startles appropriately for the exam.

Her anterior fontanel is open, soft, and flat. Her pupils are equally round and reactive to light and accommodation; a red reflex is present bilaterally. There is no nasal discharge. Her oropharynx is moist without lesions or exudates.

Her cardiovascular exam reveals a regular rate and rhythm; she has no murmurs. Her lungs are clear to auscultation. Her abdomen has appropriate bowel sounds and is soft, nondistended, and nontender.

On neurologic exam, she has symmetric facial movements, but she does not track objects to midline. She is moving all of her extremities. Tone is appropriate. Moro, grasp, and Babinski reflexes are all present.

Her skin exam reveals a cluster of erythematous papules at her right mandibular angle that includes 1 discrete vesicle.

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