Infant Head Lag

Etiology

Essentially, infant head lag can be physiological or pathological. Physiological head lag is attributed to the expected delay in the development of the neuromuscular pathway. In contrast, pathological infant head lag can be caused by myogenic and/or neurogenic deviations and several underlying problems, resulting in postural instability and axial hypotonicity.

Head lag could result from abnormal sensory functioning. Failure to detect a change in head position (attributable to abnormal feedback from the vestibular-ocular righting and proprioception systems) could lead to an inability to make the necessary motor adjustments in anticipation of a change in positioning.[3] This explanation is reasonable, considering previous research suggesting problems with anticipatory motor and postural control, and in the addition of sensory input.[8][9][8]

According to several studies, head and neck control is affected by various medical conditions such as prematurity, cerebral injury, low birth weight, and environmental factors, including extensive mechanical ventilation in the neonatal period.[10][11][12] Head lag also provides useful clinical information regarding the muscle tone of a preterm infant. The delay in head righting during infancy may be attributed to poorly developed muscle tone in preemies. Healthy preterm infants without any identifiable neurological pathology may have poor motor development, contrasted with term infants, and prolonged head lag in preterm infants has been documented even at term-equivalent age.[13][14]

Epidemiology

Head lag is more prevalent in preterm infants up to term-equivalent age; contrarily, most full-term infants can maintain their head position during the pull-to-sit test.[1][13] An article published by the American Journal of Occupational Therapy investigated changes in head lag across postmenstrual age (PMA) in infants born before 30 weeks gestation. It revealed that 90% of infants exhibited head lag at 30 weeks PMA, about 60.5% at 34 weeks PMA, and 57.8% at term-equivalent age. More head lag was also witnessed in infants who had perinatal complications.[1] 

One prospective study at Hadassah Medical Centre in Jerusalem, Israel, found that only 4% of full-term newborn infants had head lag on routine clinical examination. However, 20% of these infants with head lag had other risk factors, including vacuum delivery, probable sepsis, and congenital malformations. In the remaining 80% (i.e., the group without risk factors), 62.5% had mild head lag, and 37.5% had moderate to severe head lag.[15] 

History and Physical

The routine newborn/infant examination involves a neurological assessment of muscle tone. Head and neck control is a critical component of that examination. Mild head lag is a common finding in newborns and usually resolves by itself; however, the presence of severe persistent head lag beyond 3 to 4 months of age typically points to disorders related to hypotonia and muscle weakness in infancy.[15] Thus, obtaining a comprehensive history is crucial in narrowing the long list of differential diagnoses for hypotonia.

Specific attention must be given to pregnancy, birth history, post-natal period, developmental milestones, and family history. Perinatal risk factors include low gestational age, polyhydramnios, breech presentation, parental age, drug or teratogen exposure, consanguinity, maternal diseases (epilepsy/diabetes), congenital infections (TORCHES), or post-natal insults (sepsis and prolonged NICU stay). 

A complete physical examination is necessary to assess for potential syndromes and other associated causes of infantile hypotonia. Dysmorphic features increase the chances of CNS dysfunction as an explanation for hypotonia, and a finding of ptosis is suggestive of neuromuscular junction disorders.[16] 

When assessing tone, it helps to keep the child relaxed, not crying, and alert. Truncal and nuchal tone examination is done using vertical and horizontal suspension tests. On horizontal suspension, the infant should maintain a straight back with the head upright and limbs flexed. On vertical suspension, a vigorous infant should keep the head upright while sitting. The degree of head lag is measured by how far the head falls posteriorly behind the shoulders during the pull-to-sit test.[13] 

Head lag can be divided into three categories based on severity. Mild head lag is when the infant tries to maintain his/her head when pulled forward to a sitting position. Moderate head lag occurred when no effort was made to keep the head in an upright position while being pulled forward, but he/she could maintain the head position while sitting. Severe head lag is when an infant cannot raise his head during the pull-to-sit maneuver and failed to hold his/her head upright while sitting.[15]

Evaluation

A detailed and schematic approach is required in the evaluation of a newborn with head lag. This approach starts with a comprehensive clinical examination and history. Isolated infant head lag before 3 to 4 months, in the absence of other features of hypotonia or syndromic face, can be observed with little concern for further investigations. However, persistent head lag or severe head lag with or without other generalized hypotonia features needs to be worked extensively. 

A study in Israel found that a simple clinical test, a "feeding test,” could differentiate physiological from pathological infant head lag. In that study, healthy newborns were fed with a follow-up post-prandial reassessment of their head lag. Fifteen minutes after feeding, about 92% showed improvement or complete disappearance of head lag with a rise in serum glucose, and the remaining infants with persistent head lag were later diagnosed with pathological causes (Soto syndrome, hypothyroidism, and cerebral palsy).[15] 

Investigations to consider based on the suspected differential diagnosis for pathological head lag include TSH, free T4, electrolytes (including calcium), septic screen, and more specific tests like CT/MRI head/neck, EEG, karyotype, urine and serum amino acids, urine organic acids, blood gas, serum ammonia, liver function tests, aldolase, creatine kinase and appropriate referral to a neurologist.[17]

Treatment / Management

Physiological infant head lag has a benign presentation, and watchful waiting is most times sufficient, as most of the cases will resolve before the age of four months (and four months corrected gestational age in preterm infants) without any intervention. However, an interdisciplinary approach is required to assess and manage pathological head lag (i.e., persistent head lag after four months or severe head lag before four months of age) while addressing the underlying etiology. A pediatrician, child neurologist, medical geneticist, a physical and occupational therapist can work together to accomplish optimal results.

Systematic reviews have demonstrated that early intervention, through specific motor training routines and global developmental programs where parents are taught how to promote infant development, maybe the most reliable approach to promoting infant motor and cognitive development for groups at risk of developmental motor disorder.[18] Occupational therapists and physical therapists play an essential role in addressing sensorimotor skills to improve infants' participation. Some motor training routines include home exercises like reverse cradling, tummy time, toys, and strengthening the neck muscles.(A1)

Differential Diagnosis

Most pathologic causes of infant head lag are linked to conditions causing neonatal/infantile hypotonia. These conditions make up a list of differential diagnoses to consider when assessing an infant with persistent or severe head lag. This includes chromosome disorders (i.e., Prader Willi), Hypoxic-ischemic injuries, cerebral dysgenesis, spinal cord injuries, spinal muscular atrophies, congenital hypomyelination neuropathy, familial dysautonomia, infantile neuronal degeneration, CNS infections (i.e., meningitis and encephalitis), infantile botulism, congenital and transient myasthenia gravis, muscular dystrophies, metabolic myopathies (i.e., hypothyroidism), central core disease/fiber myopathies and other congenital myopathies.[17]

Prognosis

Otherwise, healthy infants with physiological head lag have a good prognosis; typically, symptoms resolve without intervention. On the other hand, pathological head lag is dependent on early effective physical therapy and treatment of the underlying etiology.

Complications

Infants with head lag can have trouble breastfeeding due to poor latching. Other problems are specific to the associated secondary cause, e.g., respiratory distress in infantile myasthenia gravis.