Abusive Head Injury as a Cause of Apparent Life-Threatening Events in Infancy

Background  An apparent life-threatening event (ALTE) refers to the sudden occurrence of a breathing abnormality, color change, or alteration in muscle tone or mental status in an infant. Several patients with ALTEs admitted to our institution were found to have sustained abusive head injuries.

Objective  To systematically examine the possible causes of ALTEs and their relative frequencies.

Study Design  Prospective consecutive case series of 243 infants younger than 12 months admitted to a tertiary care academic medical center for evaluation of an ALTE during a 32-month interval.

Results  Thirty-five different causes of ALTEs were identified. Six subjects (2.5%) were diagnosed as having abusive head injuries, or 1 admission every 5 months. Three patients died in the hospital, 2 of whom were diagnosed as having abusive head injuries.

Conclusions  A wide spectrum of diseases and disorders can precipitate an ALTE. Among them, abusive head injury, a recently recognized cause, occurs frequently enough to obligate its inclusion in the differential diagnosis. An ophthalmologic evaluation with dilated fundus examination and cranial imaging should therefore be considered early in the investigation unless another cause becomes apparent soon after admission.

AN APPARENT life-threatening event (ALTE) refers to the sudden occurrence in an infant of symptoms that appear frightening to the infant's caretakers.¹ The symptoms include breathing abnormality, color change, or alteration in muscle tone or mental status. Although the infant usually recovers quickly and has no lasting ill effects, these symptoms may signal a serious disorder. Infants who have experienced an ALTE typically undergo extensive testing in the hospital, but 23% to 39% of them are nevertheless discharged without a diagnosis.^2-4

Each year, The Children's Hospital at Westchester Medical Center admits approximately 90 patients for evaluation following ALTEs. In 1995, several of these patients were discharged with diagnoses that had not initially been included in the differential diagnosis: shaken baby syndrome.^5,6 This unexpected finding suggested the need to investigate whether inflicted head injury should be routinely considered in the evaluation of an ALTE.

The present article summarizes a 32-month prospective study of patients with ALTEs admitted to the medical center. The goals were to characterize this group of patients, ascertain the relative frequencies of different proximate causes of the events, and assess the magnitude of the problem of abusive head injury.

The Children's Hospital at Westchester Medical Center is a 104-bed tertiary care referral hospital located 32 km (20 miles) north of New York City in Westchester County. The medical center is the major academic teaching affiliate of New York Medical College. It serves patients representing a broad demographic and socioeconomic spectrum and a geographic region that includes urban, suburban, and rural areas in the Hudson Valley of New York State, northern New Jersey, western Connecticut, and New York City.

This study is based on data from a consecutive series of infants younger than 12 months who were admitted to the medical center between November 1, 1996, and June 30, 1999, after presenting to the hospital emergency department because of ALTE symptoms. To be enrolled in the study, an infant must have experienced the sudden occurrence of 1 or more of the following (from the initial history)¹:

• Breathing irregularity (eg, apnea, labored or shallow breathing, choking, and gagging)

• Color change indicative of decreased oxygenation (eg, cyanosis and pallor)

• Altered muscle tone or mental status (eg, hypotonia, hypertonia, clonic movements, and unresponsiveness)

If a patient was admitted for an ALTE more than once during the study, only the first admission has been included.

A physician data manager (V.V.M.) visited the pediatric floor of the hospital and the 14-bed pediatric intensive care unit on a daily basis to examine the histories and admitting diagnoses in the medical charts of all newly admitted infants to identify study subjects. Patients meeting the inclusion criteria were enrolled in the study and followed up until discharge.

A standardized data collection instrument was used to record sociodemographic data, the initial history and physical examination, diagnostic testing done in the hospital, the hospital course, the final diagnosis of the attending physician of record as documented in the medical chart, and the discharge disposition. The data manager obtained this information by reviewing the hospital chart and, when necessary, obtaining clarification by speaking with the patient's physicians. She collected the data within 24 hours of admission and updated the information on a daily basis until discharge.

To support demographic comparisons between study subjects and all other patients younger than 12 months admitted to the hospital during the study, the following data were obtained from the hospital computer system: sex, date of birth, and ethnicity.

The study was approved by the institutional review board of New York Medical College.

During the 32-month study, 243 patients met the enrollment criteria (Table 1). Their mean age was 12.0 weeks (range, 3.0 days to 11.9 months). The median age of study patients was 4.2 weeks younger than that of all other admitted patients younger than 12 months (median age, 8.9 and 13.1 weeks, respectively; P<.001). Study subjects did not differ significantly from other admitted patients with respect to sex or ethnicity.

One hundred thirty patients (53.5%) had 1 ALTE spell, and 113 patients (46.5%) had 2 or more spells before admission. One hundred ninety-one patients (78.6%) had breathing irregularity, 164 (67.5%) had color change, and 163 (67.1%) had altered muscle tone or mental status (Table 2). The most common individual symptoms were apnea (52.7% of patients), cyanosis (51.0%), hypotonia (35.0%), unresponsiveness (18.1%), labored breathing (18.1%), and lethargy (16.0%). Twenty-six patients (10.7%) received prehospital resuscitation from caretakers, and 24 patients (9.9%) were resuscitated by emergency personnel. Resuscitative measures included mouth-to-mouth, chest compressions, oxygen, manual resuscitator (Ambu bag), and intubation.

There were 35 different discharge diagnoses (Table 3). Six patients (2.5%) had final diagnoses of abusive head injury. These diagnoses required evidence of intracranial hemorrhage that could not be explained by an accident or nontraumatic process and that was accompanied by other supportive findings consistent with child abuse. Those supportive findings included retinal hemorrhages; unexplained fractures involving ribs, long bones, or the skull; and unexplained abrasions or ecchymoses of the head, face, neck, or chest (Table 4).

Because 39 patients were discharged without diagnoses, some cases of child abuse might have gone undetected. Our finding of 2.5% with an abusive head injury must therefore be considered a lower limit. At the same time, only 4 of the 39 patients underwent neither a retinal examination nor a cranial imaging study, so it is unlikely that many cases of abusive head trauma were missed.

The median length of stay of study subjects was 5 days (range, 1-98 days). Eighty-two patients had subsequent events witnessed in the hospital, most of which involved apnea, seizurelike activity, or cyanosis. Three subjects died in the hospital. They were 5 weeks, 4 months, and 7 months of age, with a final diagnosis of unknown cause in the 5-week-old and diagnoses of abusive head injury in the other 2.

The concept of a sudden, unanticipated, near-fatal event in an infant began to receive attention about 25 years ago. Such an event was referred to as near-miss for sudden infant death syndrome because of the perceived close relation to sudden infant death syndrome.^7-9 The term apparent life-threatening event entered the medical literature in the late 1980s to distinguish it more clearly from sudden infant death syndrome, as it became evident that no definite link could be established.^2,3,10,11 In 1986, ALTE was officially defined by the National Institute of Child Health and Human Development.¹

Researchers have examined potential causes of ALTEs at the microscopic and macroscopic levels. Many disorders present with similar symptoms, but the connection between specific diseases and an ALTE remains controversial. Recent studies^4,12,13 have focused on the heterogeneity of this disorder and the need to establish guidelines for evaluation and treatment.

The possibility of a link between ALTEs and abusive head injury came to our attention in 1995, when 5 patients admitted to our medical center for evaluation of an ALTE were found to have shaken baby syndrome.⁵ The initial history and physical examination revealed no apparent cause, but the discovery of retinal hemorrhages in 4 of the infants and the development of focal seizures in the fifth patient prompted further evaluation that led to the diagnosis of child abuse.

The occurrence of several cases of inflicted head injury in our 32-month series has corroborated earlier observations⁵ and other recently reported findings of child abuse among patients with ALTEs.¹⁴ In the present series, 1 in 40 (95% confidence interval, 1 in 20 to 1 in 100) ALTE admissions was linked to an abusive head injury, which translates to approximately 1 admission every 5 months. Because an infant who has sustained an abusive head injury may appear well on presentation, with no external signs of abuse,^5,15,16 intentional head injury must be considered in a patient who has an ALTE unless an alternative cause is readily apparent.

Several forms of child abuse other than inflicted head injury have been implicated in ALTEs: intentional poisoning,¹⁷ intentional smothering,¹⁸ and Munchausen syndrome by proxy.¹⁹ Because all of these are difficult to diagnose, physicians must be vigilant to avoid overlooking instances of child abuse. Toxicology screens are needed to rule out intentional or unintentional poisoning.¹⁷ A history of bleeding from the nose and mouth, or unexplained apneas occurring only in the presence of the same caregiver, suggests the possibility of intentional smothering.^18,20 Investigators have used covert video surveillance of parent-infant interactions to confirm suspected cases of intentional suffocation and Munchausen syndrome by proxy.²⁰

A 1993 study²¹ reported a series of 157 patients with severe ALTEs in which abuse (deliberate suffocation or fabricated history and data) accounted for 32% of diagnosed cases. This alarmingly high percentage underscores the need to investigate various forms of child abuse when evaluating patients with ALTEs—a task that requires a team approach with expertise from psychiatry, social work, child protective services, and law enforcement.

A wide spectrum of diseases and disorders can precipitate an ALTE. Among them, abusive head injury—a recently recognized cause—occurs frequently enough to obligate its inclusion in the differential diagnosis even if the physician observes no clues suggestive of an intracranial pathologic condition. Therefore, unless the physical examination and initial test results strongly suggest another cause, the clinician should consider taking steps to evaluate a possible inflicted injury, beginning with a dilated funduscopic examination and head imaging studies.

Article

Corresponding author and reprints: Robin L. Altman, MD, Department of Pediatrics, New York Medical College, Munger Pavilion, Valhalla, NY 10595 (e-mail: robin_altman@nymc.edu).

Accepted for publication April 15, 2003.

This study was supported by grant R03 HD35189 from the National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Md.

We thank Scott Schroeder, MD, for helping develop the initial idea for this study; and Patricia Patrick, BS, and Amy Cleary, BA, for assistance with data management.

Infants who have had an ALTE often appear normal by the time they receive medical attention. Although a wide spectrum of diseases and disorders can precipitate such an event, many of these patients never receive a definitive diagnosis even after extensive testing. Evaluation of an ALTE can therefore be a difficult and frustrating process.

The present study, based on a consecutive series of 243 patients with ALTEs, confirms a hypothesized link between abusive head injury and ALTEs. This cause occurs frequently enough to obligate its inclusion in the differential diagnosis.