Case 2: Acute lethargy in a two-month-old infant

A previously healthy eight-week-old male infant was transferred from a peripheral hospital after presenting with acute lethargy. During a visit with his father for the weekend, the child apparently awoke with an intense episode of loud and unusual crying lasting 20 min, followed by a decreased level of consciousness with no associated abnormal movements or cyanosis. He had been well just before the event, with no fever, vomiting, diarrhea or rash. His parents brought him to their community hospital, where he was noted to be lethargic and difficult to arouse, with pale, mottled skin and a rectal temperature of 35ºC. Intravenous ceftriaxone, vancomycin and acyclovir were immediately started for possible sepsis before blood and cerebrospinal fluid cultures were drawn.

The infant was otherwise healthy following an uncomplicated prenatal course and term vaginal delivery with a birthweight of 3.6 kg. The mother and father, aged 18 and 20 years, respectively, were healthy and had no other children.

After transfer from the peripheral site approximately 8 h after the initial episode, his level of consciousness was appropriate and he was interacting normally. Vital signs were stable, with a temperature of 37.8ºC, and his weight was 5.5 kg. The anterior fontanelle was full, but not tense, and the neurological examination was normal. His retinas were not examined. The rest of the physical examination was unremarkable.

A cranial ultrasound performed in the periphery was reportedly normal. A full septic workup was performed following transfer and initiation of antimicrobials. Complete blood count and urine dip were within normal limits. Cerebrospinal fluid appeared bloody, with negative Gram stain, 200×10⁶/L leukocytes (48% neutrophils), 49,800×10⁶/L erythrocytes, 1.13 g/L protein and 2.6 mmol/L glucose (62% of blood glucose). Coagulation studies were normal, and serum glucose was 4.2 mmol/L. Electrocardiogram, toxicology screen, metabolic amino acid screen and abdominal ultrasound were all normal. Further testing revealed the diagnosis.

CASE 2 DIAGNOSIS: SHAKEN BABY SYNDROME

Based on a history of intense crying followed by lethargy and a decreased level of consciousness, the differential diagnosis included sepsis, meningitis or encephalitis, head trauma (including shaken baby syndrome [SBS]), intussusception, seizure disorder, toxic ingestion, cardiac arrhythmia or inborn errors of metabolism. A cranial computed tomography (CT) scan was performed, which revealed multiple acute subdural hematomas (Figure 3). Ophthalmological examination after pupil dilation revealed pre-, sub- and intraretinal hemorrhages in the left eye, extending throughout the entire retina, including its peripheral edge. Vitreous hemorrhage was also present. These findings were suggestive of SBS; this was later confirmed when the father admitted to having shaken the infant in response to the inconsolable crying.

Figure 3.

An acute parafalcine subdural hematoma can be seen on this cranial computed tomography scan with contrast

SBS is frequently defined as a constellation of intracranial, intraocular, cervical spine and skeletal injuries resulting from nonaccidental injury in infants. It occurs when an infant is subjected to rapid acceleration, deceleration and rotational forces, and accounts for 95% of fatal or life-threatening injuries attributed to child abuse. While it is suggested that a minimum of 40 cases of SBS occur per year in Canada, the true incidence is unknown due to the number of cases that do not receive medical attention and the high rates of missed diagnoses (1).

The diagnosis of SBS often requires a high index of suspicion because the signs and symptoms may be mild and nonspecific. The common manifestations of vomiting, fever, irritability and lethargy are seen in a myriad of conditions, making it difficult to discern when further investigation for head trauma is warranted. A five-year retrospective study (2) in the United States found that the diagnosis of SBS was initially missed despite symptoms in 31% of cases; a mean of 2.8 physician visits were required for the correct diagnosis of these cases. The most common misdiagnoses were viral gastroenteritis or influenza, ‘accidental’ head injury, and ‘rule-out sepsis’. These findings, of course, do not account for those cases that were never diagnosed.

Close attention to the often vague history and an assessment of risk factors is necessary when evaluating a patient for possible SBS. A typical antecedent to the abuse is inconsolable crying leading to caretaker frustration. A 2003 retrospective study of SBS in Canada (1) identified the most common perpetrator to be the biological father, and reported a median patient age of 4.6 months. Suggested risk factors include young and/or single parents, families from low socioeconomic and educational backgrounds, and a history of previous abuse by the perpetrator.

When SBS is suspected, initial investigations should include a cranial CT scan, skeletal survey and dilated retinal examination by an ophthalmologist. Intracranial findings in SBS patients, in order of decreasing prevalence, include subdural hematoma, retinal hemorrhage, cerebral edema and subarachnoid hematoma. Cranial ultrasound cannot be relied on because it provides only a partial view of the brain, but magnetic resonance imaging is particularly useful for equivocal CT findings. Nevertheless, CT scans are preferred for acute subarachnoid or subdural hemorrhage.

Cerebrospinal fluid (CSF) samples are frequently obtained by lumbar puncture as part of a full septic workup in these patients. Given that up to 20% of all paediatric lumbar punctures are traumatic (3), blood in the CSF is often attributed to this, without evaluation for subarachnoid hemorrhage (SAH) as a potential cause. Numerous methods can be used to look for SAH when a bloody CSF sample is obtained. High opening pressure on lumbar puncture and persistent erythrocyte count elevation in consecutive tube samples are all suggestive of SAH. Centrifuging the sample soon after obtaining the CSF may reveal a yellow-coloured, or xanthochromic, supernatant indicative of oxyhemoglobin or bilirubin products of red blood cell lysis. Because one would not expect these products in sufficient quantities within 2 h of a simple traumatic tap, xanthochromia during this time frame is suggestive of a bleed of longer duration, as in SAH.

SBS has been associated with a 19% mortality rate as a direct result of the shaking injury (1). Morbidity is significant, with 55% (1) exhibiting persistent neurological deficit; long-term outcomes are unknown. Given the high number of missed cases, it has been speculated that many children with mild neurological abnormalities and learning disabilities may have previously been victims of SBS. Therefore, one must always maintain a high index of suspicion when evaluating infants with nonspecific presentations. Reasonable grounds for suspicion of child abuse require a prompt report to the local Children’s Aid Society, and a correct diagnosis of SBS can allow for appropriate management and prevention of further abuse.

CLINICAL PEARLS

• SBS should be considered as part of the differential diagnosis in any infant with acute onset of lethargy or other nonspecific findings. Close attention to the history, assessment of risk factors for abuse, and head-to-toe physical examination are all warranted in these cases. However, because a normal physical examination and apparent absence of risk factors does not exclude a diagnosis of SBS, a low threshold for diagnostic imaging is needed in such cases to rule out occult skeletal or intracranial injury.

• A bloody CSF specimen should be centrifuged soon after lumbar puncture to assess for xanthochromic supernatant suggestive of subarachnoid hemorrhage.

• Head ultrasound is not a sensitive test for intracranial hemorrhage. Head CT, skeletal survey and dilated retinal examinations are the modalities of choice when assessing for features of SBS.