Discharge Best Practices of High-Risk Infants From Regional Children's Hospital NICUs

OBJECTIVES

Lack of discharge preparedness after NICU hospitalization is associated with risk of readmission and parental stress. Complex infants cared for at regional children's hospital NICUs would benefit from a systematic approach to transition home. Our objective was to identify potential best practices for NICU discharge and examine priorities for incorporating these best practices in regional children's hospital NICUs.

METHODS

We used techniques from quality improvement, including fish bone and key driver diagrams, yielding 52 potential best practice statements for discharge preparation. Using the modified Delphi method, we surveyed stakeholders on their level of agreement for the statement to be included in the final guideline regarding discharge processes and parental education. Consensus was defined as 85% agreement among respondents. To identify implementation feasibility and understand unit-level priorities, a prioritization and feasibility assessment survey was used to rank the top best practices and performed gap analyses for the first prioritized intervention.

RESULTS

Fifty of the 52 statements met the predefined criteria for consensus. The prioritization survey of potential best practice statements named assessment of families' social determinants of health with a standardized tool as the top priority among respondents. Conducting gap analyses enabled an understanding of current practice, barriers, and affordances, allowing for implementation planning.

CONCLUSIONS

This multicenter and interdisciplinary expert panel reached a consensus on multiple potential best practices for complex discharge preparation from regional children's hospital NICUs. Better support for families navigating the complex NICU discharge process has the potential to improve infant health outcomes.

Association of Hospital Resource Utilization With Neurodevelopmental Outcomes in Neonates With Hypoxic-Ischemic Encephalopathy

IMPORTANCE

Intercenter variation exists in the management of hypoxic-ischemic encephalopathy (HIE). It is unclear whether increased resource utilization translates into improved neurodevelopmental outcomes.

OBJECTIVE

To determine if higher resource utilization during the first 4 days of age, quantified by hospital costs, is associated with survival without neurodevelopmental impairment (NDI) among infants with HIE.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective cohort analysis of neonates with HIE who underwent therapeutic hypothermia (TH) at US children's hospitals participating in the Children's Hospitals Neonatal Database between 2010 and 2016. Data were analyzed from December 2021 to December 2022.

EXPOSURES

Infants who survived to 4 days of age and had neurodevelopmental outcomes assessed at greater than 11 months of age were divided into 2 groups: (1) death or NDI and (2) survived without NDI. Resource utilization was defined as costs of hospitalization including neonatal neurocritical care (NNCC). Data were linked with Pediatric Health Information Systems to quantify standardized costs by terciles.

MAIN OUTCOMES AND MEASURES

The main outcome was death or NDI. Characteristics, outcomes, hospitalization, and NNCC costs were compared.

RESULTS

Among the 381 patients who were included, median (IQR) gestational age was 39 (38-40) weeks; maternal race included 79 (20.7%) Black mothers, 237 (62.2%) White mothers, and 58 (15.2%) mothers with other race; 80 (21%) died, 64 (17%) survived with NDI (combined death or NDI group: 144 patients [38%]), and 237 (62%) survived without NDI. The combined death or NDI group had a higher rate of infants with Apgar score at 10 minutes less than or equal to 5 (65.3% [94 of 144] vs 39.7% [94 of 237]; P < .001) and a lower rate of infants with mild or moderate HIE (36.1% [52 of 144] vs 82.3% [195 of 237]; P < .001) compared with the survived without NDI group. Compared with low-cost centers, there was no association between high- or medium-hospitalization cost centers and death or NDI. High- and medium-EEG cost centers had lower odds of death or NDI compared with low-cost centers (high vs low: OR, 0.30 [95% CI, 0.16-0.57]; medium vs low: OR, 0.29 [95% CI, 0.13-0.62]). High- and medium-laboratory cost centers had higher odds of death or NDI compared with low-cost centers (high vs low: OR, 2.35 [95% CI, 1.19-4.66]; medium vs low: OR, 1.93 [95% CI, 1.07-3.47]). High-antiseizure medication cost centers had higher odds of death or NDI compared with low-cost centers (high vs. low: OR, 3.72 [95% CI, 1.51-9.18]; medium vs low: OR, 1.56 [95% CI, 0.71-3.42]).

CONCLUSIONS AND RELEVANCE

Hospitalization costs during the first 4 days of age in neonates with HIE treated with TH were not associated with neurodevelopmental outcomes. Higher EEG costs were associated with lower odds of death or NDI yet higher laboratory and antiseizure medication costs were not. These findings serve as first steps toward identifying aspects of NNCC that are associated with outcomes.

Health Care Disparities in High-Risk Neonates

Long-standing health disparities in maternal reproductive health, infant morbidity and mortality, and long-term developmental outcomes are rooted in a foundation of structural racism. Social determinants of health profoundly affect reproductive health outcomes of Black and Hispanic women disproportionately; they have higher rates of death during pregnancy and preterm birth. Their infants are also more likely to be cared for in poorer quality neonatal intensive care units (NICUs), receive poorer quality of NICU care, and are less likely to be referred to an appropriate high-risk NICU follow-up program. Interventions that mitigate the impact of racism will help to eliminate health disparities.

Aberrant somatosensory phase synchronization in children with hemiplegic cerebral palsy

Children with hemiplegic cerebral palsy (HCP) often show disturbances of somatosensation. Despite extensive evidence of somatosensory deficits, neurophysiological alterations associated with somatosensory deficits in children with HCP have not been elucidated. Here, we aim to assess phase synchrony within and between contralateral primary (S1) and secondary (S2) somatosensory areas in children with HCP. Intra-regional and inter-regional phase synchronizations within and between S1 and S2 were estimated from somatosensory evoked fields (SEFs) in response to passive pneumatic stimulation of contralateral upper extremities and recorded with pediatric magnetoencephalography (MEG) in children with HCP and typically developing (TD) children. We found aberrant phase synchronizations within S1 and between S1 and S2 in both hemispheres in children with HCP. Specifically, the less-affected (LA) hemisphere demonstrated diminished phase synchronizations after the stimulus onset up to ~120 ms compared to the more-affected (MA) hemisphere and the dominant hemisphere of TD children, while the MA hemisphere showed enhanced phase synchronizations after ~100 ms compared to the LA hemisphere and the TD dominant hemisphere. Our findings indicate abnormal somatosensory functional connectivity in both hemispheres of children with HCP.

Predictive Models of Neurodevelopmental Outcomes After Neonatal Hypoxic-Ischemic Encephalopathy

OBJECTIVES

To develop predictive models for death or neurodevelopmental impairment (NDI) after neonatal hypoxic-ischemic encephalopathy (HIE) from data readily available at the time of NICU admission ("early") or discharge ("cumulative").

METHODS

In this retrospective cohort analysis, we used data from the Children's Hospitals Neonatal Consortium Database (2010-2016). Infants born at ≥35 weeks' gestation and treated with therapeutic hypothermia for HIE at 11 participating sites were included; infants without Bayley Scales of Infant Development scores documented after 11 months of age were excluded. The primary outcome was death or NDI. Multivariable models were generated with 80% of the cohort; validation was performed in the remaining 20%.

RESULTS

The primary outcome occurred in 242 of 486 infants; 180 died and 62 infants surviving to follow-up had NDI. HIE severity, epinephrine administration in the delivery room, and respiratory support and fraction of inspired oxygen of 0.21 at admission were significant in the early model. Severity of EEG findings was combined with HIE severity for the cumulative model, and additional significant variables included the use of steroids for blood pressure management and significant brain injury on MRI. Discovery models revealed areas under the curve of 0.852 for the early model and of 0.861 for the cumulative model, and both models performed well in the validation cohort (goodness-of-fit χ²: P = .24 and .06, respectively).

CONCLUSIONS

Establishing reliable predictive models will enable clinicians to more accurately evaluate HIE severity and may allow for more targeted early therapies for those at highest risk of death or NDI.

Abnormal Nutritive Sucking as an Indicator of Neonatal Brain Injury

A term neonate is born with the ability to suck; this neuronal network is already formed and functional by 28 weeks gestational age and continues to evolve into adulthood. Because of the necessity of acquiring nutrition, the complexity of the neuronal network needed to suck, and neuroplasticity in infancy, the skill of sucking has the unique ability to give insight into areas of the brain that may be damaged either during or before birth. Interpretation of the behaviors during sucking shows promise in guiding therapies and how to potentially repair the damage early in life, when neuroplasticity is high. Sucking requires coordinated suck-swallow-breathe actions and is classified into two basic types, nutritive and non-nutritive. Each type of suck has particular characteristics that can be measured and used to learn about the infant's neuronal circuitry. Basic sucking and swallowing are present in embryos and further develop to incorporate breathing ex utero. Due to the rhythmic nature of the suck-swallow-breathe process, these motor functions are controlled by central pattern generators. The coordination of swallowing, breathing, and sucking is an enormously complex sensorimotor process. Because of this complexity, brain injury before birth can have an effect on these sucking patterns. Clinical assessments allow evaluators to score the oral-motor pattern, however, they remain ultimately subjective. Thus, clinicians are in need of objective measures to identify the specific area of deficit in the sucking pattern of each infant to tailor therapies to their specific needs. Therapeutic approaches involve pacifiers, cheek/chin support, tactile, oral kinesthetic, auditory, vestibular, and/or visual sensorimotor inputs. These therapies are performed to train the infant to suck appropriately using these subjective assessments along with the experience of the therapist (usually a speech therapist), but newer, more objective measures are coming along. Recent studies have correlated pathological sucking patterns with neuroimaging data to get a map of the affected brain regions to better inform therapies. The purpose of this review is to provide a broad scope synopsis of the research field of infant nutritive and non-nutritive feeding, their underlying neurophysiology, and relationship of abnormal activity with brain injury in preterm and term infants.

Newborn intensive care survivors: a review and a plan for collaboration in Texas

BACKGROUND

Neonatal intensive care is a remarkable success story with dramatic improvements in survival rates for preterm newborns. Significant efforts and resources are invested to improve mortality and morbidity but much remains to be learned about the short and long-term effects of neonatal intensive care unit (NICU) interventions. Published guidelines recommend that infants discharged from the NICU be in an organized follow-up program that tracks medical and neurodevelopmental outcomes. Yet, there are no standardized guidelines for provision of follow-up services for high-risk infants. The National Institute of Child Health and Human Development Neonatal Research Network and the Vermont Oxford Network have made strides toward standardizing practices and conducting outcomes research, but only include a subset of developmental follow-up programs with a focus on extremely preterm infants. Several studies have been conducted to gain a better understanding of current practices in developmental follow-up. Some of the major themes in these studies are the lack of personnel and funding to provide comprehensive follow-up care; feeding difficulties as a primary issue for NICU survivors, families, and programs; wide variability in referral and follow-up care practices; and calls for standardized, systematic developmental surveillance to improve outcomes.

FINDINGS

We convened a one-day summit to discuss developmental follow-up practices in Texas involving four academic and three nonacademic centers. All seven centers described variable age and weight criteria for follow-up of NICU patients and a unique set of developmental practices, including duration of follow-up, types and timing of developmental assessments administered, education and communication with families and other health care providers, and referrals for services. Needs identified by the centers focused on two main themes: resources and comprehensive care. Participants identified key challenges for developmental follow-up, generated recommendations to address these challenges, and outlined components of a quality program.

CONCLUSIONS

The long-term goal is to ensure that all children maximize their potential; a goal supported through quality, comprehensive developmental follow-up care and outcomes research to continuously improve evidence-based practices. We aim to contribute to this goal through a statewide working group collaborating on research to standardize practices and inform policies that truly benefit children and their families.

Postnatal weight gain in preterm infants with severe bronchopulmonary dysplasia

OBJECTIVES

To characterize postnatal growth failure (PGF), defined as weight < 10th percentile for postmenstrual age (PMA) in preterm (≤ 27 weeks' gestation) infants with severe bronchopulmonary dysplasia (sBPD) at specified time points during hospitalization, and to compare these in subgroups of infants who died/underwent tracheostomy and others.

STUDY DESIGN

Retrospective review of data from the multicenter Children's Hospital Neonatal Database (CHND).

RESULTS

Our cohort (n = 375) had a mean ± standard deviation gestation of 25 ± 1.2 weeks and birth weight of 744 ± 196 g. At birth, 20% of infants were small for gestational age (SGA); age at referral to the CHND neonatal intensive care unit (NICU) was 46 ± 50 days. PGF rates at admission and at 36, 40, 44, and 48 weeks' PMA were 33, 53, 67, 66, and 79% of infants, respectively. Tube feedings were administered to > 70% and parenteral nutrition to a third of infants between 36 and 44 weeks' PMA. At discharge, 34% of infants required tube feedings and 50% had PGF. A significantly greater (38 versus 17%) proportion of infants who died/underwent tracheostomy (n = 69) were SGA, compared with those who did not (n = 306; p < 0.01).

CONCLUSIONS

Infants with sBPD commonly had progressive PGF during their NICU hospitalization. Fetal growth restriction may be a marker of adverse outcomes in this population.

Death or neurodevelopmental impairment at 18 to 22 months corrected age in a randomized trial of early dexamethasone to prevent death or chronic lung disease in extremely low birth weight infants

OBJECTIVE

To evaluate the incidence of death or neurodevelopmental impairment (NDI) at 18-22 months corrected age in subjects enrolled in a trial of early dexamethasone treatment to prevent death or chronic lung disease in extremely low birth weight infants.

STUDY DESIGN

Evaluation of infants at 18-22 months corrected age included anthropomorphic measurements, a standard neurological examination, and the Bayley Scales of Infant Development-II, including the Mental Developmental Index and the Psychomotor Developmental Index. NDI was defined as moderate or severe cerebral palsy, Mental Developmental Index or Psychomotor Developmental Index <70, blindness, or hearing impairment.

RESULTS

Death or NDI at 18-22 months corrected age was similar in the dexamethasone and placebo groups (65% vs 66%, P = .99 among those with known outcome). The proportion of survivors with NDI was also similar, as were mean values for weight, length, and head circumference and the proportion of infants with poor growth (50% vs 41%, P = .42 for weight less than 10th percentile); 49% of infants in the placebo group received treatment with corticosteroid compared with 32% in the dexamethasone group (P = .02).

CONCLUSION

The risk of death or NDI and rate of poor growth were high but similar in the dexamethasone and placebo groups. The lack of a discernible effect of early dexamethasone on neurodevelopmental outcome may be due to frequent clinical corticosteroid use in the placebo group.

Impact of prenatal evaluation and protocol-based perinatal management on congenital diaphragmatic hernia outcomes

BACKGROUND/PURPOSE

Although intuitive, the benefit of prenatal evaluation and multidisciplinary perinatal management for fetuses with congenital diaphragmatic hernia (CDH) is unproven. We compared the outcome of prenatally diagnosed patients with CDH whose perinatal management was by a predefined protocol with those who were diagnosed postnatally and managed by the same team. We hypothesized that patients with CDH undergoing prenatal evaluation with perinatal planning would demonstrate improved outcome.

METHODS

Retrospective chart review of all patients with Bochdalek-type CDH at a single institution between 2004 and 2009 was performed. Patients were stratified by history of perinatal management, and data were analyzed by Fisher's Exact test and Student's t test.

RESULTS

Of 116 patients, 71 fetuses presented in the prenatal period and delivered at our facility (PRE), whereas 45 infants were either outborn or postnatally diagnosed (POST). There were more high-risk patients in the PRE group compared with the POST group as indicated by higher rates of liver herniation (63% vs 36%, P = .03), need for patch repair (57% vs 27%, P = .004), and extracorporeal membrane oxygenation use (35% vs 18%, P = .05). Despite differences in risk, there was no difference in 6-month survival between groups (73% vs 73%).

CONCLUSIONS

Patients with CDH diagnosed prenatally are a higher risk group. Prenatal evaluation and multidisciplinary perinatal management allows for improved outcome in these patients.

Neurodevelopmental outcomes of premature infants with severe respiratory failure enrolled in a randomized controlled trial of inhaled nitric oxide

OBJECTIVES

We hypothesized that inhaled nitric oxide (iNO) would not decrease death or neurodevelopmental impairment (NDI) in infants enrolled in the National Institute of Child Health and Human Development Preemie iNO Trial (PiNO) trial, nor improve neurodevelopmental outcomes in the follow-up group.

STUDY DESIGN

Infants <34 weeks of age, weighing <1500 g, with severe respiratory failure were enrolled in the multicenter, randomized, controlled trial. NDI at 18 to 22 months corrected age was defined as: moderate to severe cerebral palsy (CP; Mental Developmental Index or Psychomotor score Developmental Index <70), blindness, or deafness.

RESULTS

Of 420 patients enrolled, 109 who received iNO (52%) and 98 who received placebo (47%) died. The follow-up rate in survivors was 90%. iNO did not reduce death or NDI (78% versus 73%; relative risk [RR], 1.07; 95% CI, 0.95-1.19), or NDI or Mental Developmental Index <70 in the follow-up group. Moderate-severe CP was slightly higher with iNO (RR, 2.41; 95% CI, 1.01-5.75), as was death or CP in infants weighing <1000 g (RR, 1.22; 95% CI, 1.05-1.43).

CONCLUSIONS

In this extremely ill cohort, iNO did not reduce death or NDI or improve neurodevelopmental outcomes. Routine iNO use in premature infants should be limited to research settings until further data are available.

Real-time polymerase chain reaction for the rapid detection of group B streptococcal colonization in neonates

BACKGROUND

Group B streptococcal (GBS) infection remains a leading cause of neonatal sepsis. Currently, the management guidelines of neonates born to women with unknown GBS status at delivery are unclear. In this cohort, who undergo at least a 48-hour observation, a rapid method of detection of GBS colonization would allow targeted evaluation and treatment, as well as prevent delayed discharge.

OBJECTIVE

The goal of this research was to evaluate the validity of rapid fluorescent real-time polymerase chain reaction in comparison with standard culture to detect GBS colonization in infants born to women whose GBS status is unknown at delivery.

DESIGN/METHODS

Neonates at >32 weeks' gestation born to women whose GBS status was unknown at delivery were included. Samples were obtained from the ear, nose, rectum, and gastric aspirate for immediate culture and real-time polymerase chain reaction after DNA extraction using the LightCycler. Melting point curves were generated, and confirmatory agar gel electrophoresis was performed.

RESULTS

The study population (n = 94) had a mean +/- SD gestational age of 38 +/- 2 weeks and birth weight of 3002 +/- 548 g. The rates of GBS colonization by culture were 17% and 51% by real-time polymerase chain reaction. The 4 surface sites had comparable rates of GBS. The overall sensitivities, specificities, and positive and negative predictive values of real-time polymerase chain reaction were: 90%, 80.3%, 28%, and 98.9%.

CONCLUSIONS

Real-time polymerase chain reaction resulted in a threefold higher rate of detection of GBS colonization and had an excellent negative predictive value in a cohort of neonates with unknown maternal GBS status at delivery. Thus, real-time polymerase chain reaction would be a useful clinical tool in the management of those infants potentially at risk for invasive GBS infection and would allow earlier discharge for those found to be not at risk.

Altered prostaglandin E1 dosage during extracorporeal membrane oxygenation in a newborn with ductal-dependent congenital heart disease

We describe a neonate with ductal-dependent congenital heart disease on extracorporeal membrane oxygenation (ECMO) for persistent pulmonary hypertension, who required markedly high doses of prostaglandin E1 (PGE1) to maintain patency of the ductus arteriosus: The effects of ECMO on the pharmacokinetics of PGE1 are discussed.

Postmarketing surveillance for human teratogenicity: a model approach

BACKGROUND

Most congenital defects associated with prenatal exposures are notable for a pattern of major and minor malformations, rather than for a single major malformation. Thus, traditional epidemiological methods are not universally effective in identifying new teratogens. The purpose of this report is to outline a complementary approach that can be used in addition to other more established methods to provide the most comprehensive evaluation of prenatal exposures with respect to teratogenicity.

METHODS

We describe a multicenter prospective cohort study design involving dysmorphological assessment of liveborn infants. This design uses the Organization of Teratology Information Services, a North American network of information providers who also collaborate for research purposes. Procedures for subject selection, methods for data collection, standard criteria for outcome classification, and the approach to analysis are detailed.

RESULTS

The focused cohort study design allows for evaluation of a spectrum of adverse pregnancy outcomes ranging from spontaneous abortion to functional deficit. While sample sizes are typically inadequate to identify increased risks for single major malformations, the use of dysmorphological examinations to classify structural anomalies provides the unique advantage of screening for a pattern of malformation among exposed infants.

CONCLUSIONS

As the known human teratogens are generally associated with patterns of structural defects, it is only when studies of this type are used in combination with more traditional methods that we can achieve an acceptable level of confidence regarding the risk or safety of specific exposures during pregnancy.

The effectiveness of risk-based intrapartum chemoprophylaxis for the prevention of early-onset neonatal group B streptococcal disease

OBJECTIVE

Our purpose was to evaluate the effectiveness of a risk-based intrapartum antibiotic prophylaxis strategy for the prevention of early-onset neonatal group B streptococcal disease.

STUDY DESIGN

Cases and controls were selected from infants born to women with one or more risk factors: preterm labor or rupture of membranes, prolonged rupture of membranes (>18 hours), fever during labor, or previous child with group B streptococcal disease. Cases were matched with controls by birth hospital and gestational age. Data abstracted from medical records were analyzed to estimate the effectiveness of intrapartum antibiotic prophylaxis.

RESULTS

We analyzed data from 109 cases and 207 controls. Nineteen (17%) case versus 69 (33%) control mothers received an acceptable regimen of intrapartum antibiotic prophylaxis. In adjusted analyses, the effectiveness of intrapartum antibiotic prophylaxis was 86% (95% confidence interval, 66%-94%). When the first dose of antibiotics was given > or =2 hours before delivery, the effectiveness increased to 89% (95% confidence interval, 70%-96%); when it was given within 2 hours of delivery, the effectiveness was 71% (95% confidence interval, -8%-92%). Effectiveness was lowest in mothers with intrapartum fever (72%, 95% confidence interval, -9%-93%). On the basis of a 70% prevalence of maternal risk factors expected among cases in the absence of intrapartum antibiotic prophylaxis, we estimate that the risk-based strategy could reduce early-onset group B streptococcal disease by 60%.

CONCLUSIONS

The risk-based approach to intrapartum antibiotic prophylaxis is effective in preventing early-onset group B streptococcal disease. To achieve the maximum preventive effect, the first dose of antibiotics should be administered at least 2 hours before delivery.

Does changing paternity contribute to the risk of intrauterine growth retardation?

An immune reaction initiated by paternal antigens may be necessary for healthy placental development, pregnancy maintenance and infant growth. An inadequate immune response may result in intrauterine growth retardation (IUGR). We hypothesised that a change in paternity may interfere with the immune response and cause poor placentation with resultant IUGR. In this paper we examine the risk of IUGR associated with changes in paternity. We used the Utah Successive Pregnancies Data Set that contains information on women across their pregnancies. We restricted the analysis to 141,817 women with two or three pregnancies. Women who did not have an IUGR infant in the previous pregnancy were at a 20-30% greater risk of developing IUGR if they had changed partners. Women who had a previous IUGR infant were at no increased risk for IUGR after a change in paternity. These results may point to an immune mechanism or may be as a result of residual confounding of unmeasured risk factors for IUGR. Further studies with data that contain more sociodemographic and biological risk factors for IUGR are necessary to exclude residual confounding.

Mammalian muscle cells bear a cell-autonomous, heritable memory of their rostrocaudal position

We previously documented a greater than 100-fold rostrocaudal gradient of chloramphenicol acetyltransferase (CAT) expression in the muscles of adult mice that bear a myosin light chain-CAT transgene: successively more caudal muscles express successively higher levels of CAT. Here we studied the development and maintenance of this positional information in vitro. CAT levels reflect the rostrocaudal positions of the muscles from which the cells are derived in cultures established from adult muscles, in clones derived from individual adult myogenic (satellite) cells, in cultures prepared from embryonic myoblasts, and in cell lines derived by retrovirus-mediated transfer of an oncogene to satellite cells. Our results suggest that myoblasts bear a positional memory that is established in embryos, retained in adults, cell autonomous, heritable, stable to transformation, and accessible to study in clonal cell lines.

Selective expression of an acetylcholine receptor-lacZ transgene in synaptic nuclei of adult muscle fibers

Acetylcholine receptors (AChRs) are highly concentrated in the postsynaptic membrane at the neuromuscular junction. To investigate mechanisms that lead to the formation or maintenance of this synaptic specialization, we generated transgenic mice in which regulatory elements from the AChR alpha or epsilon-subunit genes are linked to a gene for a reporter protein that is targeted to the nucleus (nlacZ). Both transgenes were selectively expressed and developmentally regulated in muscle; nuclei in both extrafusal (ordinary) and intrafusal (spindle) muscle fibers were labeled. Within individual muscle fibers from epsilon-nlacZ mice, nuclei near synaptic sites were nlacZ-positive, whereas extrasynaptic nuclei were nlacZ-negative. In contrast, nlacZ was expressed in both synaptic and extrasynaptic nuclei when under the control of regulatory elements from the AChR alpha-subunit gene; however, synaptic nuclei were somewhat more intensely stained than extrasynaptic nuclei in a minority of muscle fibers from these mice. Together, our results provide direct evidence for molecular differences between synaptic and extrasynaptic nuclei within a single cytoplasm, and suggest that the motor nerve regulates synapse formation by selectively affecting transcription in synaptic nuclei.