Case 1 - Toxic Infant With a Full Fontanelle

Volume 1, Case 1
Loren G. Yamamoto, MD, MPH
Kapiolani Medical Center For Women And Children
University of Hawaiʻi John A. Burns School of Medicine

This is a 5-month old male with fever, irritability, and vomiting. His temperature at home was 38.0 rectally. He vomited five times since onset 8 hours ago. He is feeding soy formula. Past medical history is unremarkable.

Exam: VS T38.0R, P150, R40 (crying), BP unobtainable, wt 50%ile. Fussy, though consolable at times. He doesn't focus or interact well and appears somewhat "toxic" to the examiner. Anterior fontanelle is somewhat full, but he is crying so it is difficult to truly assess. Eyes moist. Pupils reactive. TM's are shiny and slightly red. Oral mucosa moist. Neck is hard to assess due to crying. Heart regular without murmur. Lungs clear. Abdomen soft on inspiration. No detectable tenderness evident. No hernias. Testes not swollen. CVA tenderness is not apparent. Color slightly pale. Capillary refill time 2-3 seconds. Muscle tone good.

A lumbar puncture is done to rule out meningitis. The CSF is homogeneously bloody (blood mixed with CSF). The blood does not clear. All three tubes appear to be equally bloody. A CBC, blood culture, and catheterized urine sample are sent to the lab. An IV is started and the child is given 50mg/kg of cefotaxime IV. A CT scan is done to rule out subarachnoid hemorrhage.

View CT scan image.

This CT scan was done without IV contrast. It was read as a posterior inter-hemispheric subdural hematoma. It shows blood in the subdural space and an increased density (whiter than it should be) of the posterior falx secondary to a posterior inter-hemispheric subdural hematoma. Other clinical findings and a social investigation confirmed the etiology as shaken baby syndrome.

Teaching Points:

1. Although the falx may enhance with IV contrast, an increased density of the posterior falx before IV contrast is administered should raise the suspicion of a posterior interhemispheric subdural hematoma. This injury is highly indicative of a shaken baby. Other findings such as retinal hemorrhages and a suspicious history add to the strength of this etiology.
2. An experienced physician who has done many lumbar punctures in infants usually knows when to expect bloody CSF due to the difficulty of the procedure. If bloody CSF is unexpectedly encountered, and it does not clear, one should be highly suspicious of intracerebral hemorrhage with blood entering the subarachnoid space.
3. Although blood should not appear in the CSF if the hemorrhage is purely subdural, this injury is not purely subdural in nature. Blood also enters the subarachnoid space. Axonal shearing and generalized cerebral cellular injury take place as well.
4. A full fontanelle is not always indicative of meningitis. Intracerebral hemorrhage, cerebral edema, and acute hydrocephalus can all mimic the same clinical features.
5. Trauma specialists have often taught that intracranial hemorrhage alone cannot account for all the blood loss in a patient in hypovolemic shock. In other words, if you have diagnosed an intracerebral hemorrhage in a trauma patient in hypovolemic shock, you must look elsewhere for additional hemorrhaging sites, such as in the abdomen. Infants appear to violate this rule since many shaken babies present to the emergency department in shock. Although one must always be suspicious of other hemorrhaging sites from injuries such as from fractures and internal injuries, subsequent work-ups on these patients may fail to identify significant hemorrhaging sites other than in the brain.
6. CT scans may fail to show a posterior inter-hemispheric subdural hematoma if it is small. MRI scanning has been shown to be more sensitive at identifying these hemorrhages and other brain injuries.

References:

1. Ludwig S. Child Abuse. In: Fleisher GR, Ludwig S, eds. Textbook of Pediatric Emergency Medicine, third edition. Baltimore, MD, Williams and Wilkins, 1993, p. 1437.
2. Bogost GA, Crues JV, Moser FG. MR Imaging in the Evaluation of Trauma. Emergency Radiology 1994;1(1):1-14.
3. Sklar EM, Quencer RM, Bowen BC, Altman N, Villanueva PA. Magnetic resonance applications in cerebral injury. Radiology Clinics of North America 1992;30(2):353-366.
4. Barkovich AJ. Chapter 4 - Destructive Brain Disorders of Childhood. In: Pediatric Neuroimaging, second edition. New York, Raven Press, 1995, pp. 167-170.