Anna Packard, Jotham Manwaring and Dr. Ramona Hopkins, Psychology
A significant increase in misshapen or flattened heads (positional plagiocephaly) in infants has been recognized since pediatricians began advising parents to position their infants supine for sleep in 1992 in order to diminish the risk for Sudden Infant Death Syndrome (Back-to-Sleep Program, American Academy of Pediatrics, 1992). Prior to 1992, the incidence of positional plagiocephaly was quite rare (< 1/300) [Capri, 1999] and was usually observed in children who were neglected, institutionalized, or developmentally delayed (Figure 1). Recent research has found an association between supine positioning for sleep as a result of the Back-to-Sleep program and plagiocephaly (Turk, 1996). The incidence of plagiocephaly is now greater than 1/50 newborns (Kane, Mitchell, and Craven, 1996), resulting in upwards of 20 new referrals for cranial asymmetry per week in one of the authors’ clinical practice (KHM). Other unintended consequences of the Back to Sleep Program include a change in the roundedness of the head in the new generation of children. Prior to 1992 the normal Caucasian cephalic index or ratio of width-to-length was mean of 0.76; now it is 0.85 to 0.90 and this appears to be permanent. In addition, the infants with plagiocephaly have been shown to have delayed acquisition of gross motor skills, such as of rolling over and sitting, by approximately 2 months. Additionally, evidence of diminished motor coordination at 6 years has been showed compared to normocephalics peers.
Information regarding why some infants develop the oblique head shape of positional plagiocephaly compared to normocephalic infants when placed supine for sleep is lacking. Many health care professionals attribute the change in head shape as a result of decreased activity due to the infants’ “personality” (i.e. vulnerable infants appear to be less active, more easily consoled, and quieter in sleep). Delays in milestones suggest a “neurologic” basis may exist. Since the typical infant sleeps more than 16 hours per day, we determined that information regarding the mechanism(s) of plagiocephaly could be obtained by monitoring the infant’s sleep positions and activity coupled with a measure to determine depth of consciousness during sleep. We hypothesized that infants with positional plagiocephaly would have decreased arousal and activity (i.e. self re-positioning frequency) compared to their normal cohorts. In addition, we were interested in whether these infants have normal EEG patterns, compared to their normal cohorts, during sleep.
To conduct this study, we used two mechanisms of measurement. To measure sleep positions and activity throughout the night we used Gotchaâ, a home security camera system that employs a motion detection algorithm to monitor movement. We combined this system with an infrared camera placed over the crib for non-intrusive monitoring of movement. We used the Bispectral Indexâ (BISâ) monitor to measure the EEG patterns of the infants. This enabled us to measure the depth of sleep throughout the night. We monitored the sleep patterns of twenty infants, ages 3-5 months. We divided the infants into an experimental group (those with positional plagiocephaly) and a control group (the normocephalic infants). We analyzed the data obtained from two nights of monitoring for each infant and compared the sleep patterns of the experimental group with the control group.
We are still in the process of evaluating our results due to unforeseen complications. One problem is that of interpreting the data from the BIS monitor. Since there are only a couple published articles regarding the accuracy of using the BIS machine to monitor sleep, along with the scarce published research on infant sleep patterns, we do not feel we can define the stages of sleep in infants we monitored in the conventional nomenclature (stages I-IV, REM). We met with a pediatric neurologist to compare the data of a sleeping infant using both the standard electroencephalogram and BIS machine. Based on the EEG pattern, he indicated REM sleep and lightest stage sleep (stage I) in infants could be quantified by using the BIS monitor score of 75 or above (range of 0-100). We intend to use this as a marker to determine the amount of time an infant spends in REM sleep during the night of monitoring. Preliminarily, we have demonstrated that infants show the expected approximate 50% of sleep in such dream or slight sleep phases.
In spite of this problem, we have been able to accomplish one of our main goals; that of counting the number of times the infants reposition throughout the night. In order to do this, we had to define a “reposition” as moving the head to a new position and remaining in that position for a minimum of five minutes. We also had to define a “movement” as any movement where the infant’s head returned to its previous position, or did not stay in a new position for the required five minutes. These definitions enabled us to determine how many times the infants repositioned and moved their heads throughout the night and quantify the two groups.
Our hypothesis was that infants with positional plagiocephaly would not reposition as frequently as their normal cohorts, leading to the increased deformation of their cranium. Our preliminary findings show this to be true. The plagiocephalic infants tended to keep their heads in the same position throughout the night. Further, we discovered that they tended to favor the flattened side of their skull. This is also consistent with our hypothesis. However, we found that infants with positional plagiocephaly did not seem to be as “quiet” or motionless during sleep as we had predicted. It appears that plagiocephalic infants move as frequently as normocephalic infants. However, a key difference is that plagiocephalic infants exhibit decreased frequency of repositioning. We believe that our recordings accurately represent normal sleep. We monitored each infant for two nights and used the data from the second night of sleep to ensure accurate measurement (i.e. the infant is acclimated to the sensors). Our preliminary findings, however, require further investigation to draw final conclusions. We intend to conclude this study by the beginning of March 2004, and we believe that the results will reveal new insights into why certain children are prone to plagiocephaly. Our results may lead to new methods of early detection and intervention.