Hot Seat #227 Denouement
Posted on: April 25, 2024, by : Brandon Ho
This week’s case discussion focuses on a partially vaccinated 14-month-old presenting with a fever and a bulging fontanelle. Key discussion points included the choice between ultrasound and CT imaging, the necessity for empiric antibiotics, and the considerations for performing a lumbar puncture.
Assessing the fontanelle when the child is calm is essential, as a bulging appearance might simply be due to crying. Clarification is necessary to determine if the child is truly inconsolable or if they can be soothed.
Imaging: Ultrasound vs. CT
In this case, the decision between ultrasound and CT imaging was critical. Head ultrasound in infants has limited sensitivity for detecting intracranial abnormalities beyond the ventricles, as it can only visualize areas accessible through open fontanelles and suture lines. Its specificity is high for conditions it can detect, such as hydrocephalus or severe ventriculomegaly. While it has good specificity, its sensitivity is poor, making it more suitable for ruling in rather than ruling out conditions. Due to its limitations in visualizing certain brain areas, further imaging with CT or MRI may be necessary for a comprehensive evaluation when increased intracranial pressure is suspected.
Empiric Antibiotics
The consensus among participants leaned towards initiating empiric antibiotics. While it is reasonable to order antibiotics and hold administration until after imaging and lumbar puncture, provided these can be performed quickly.
Lumbar Puncture: To Perform or Not to Perform
Despite the child testing positive for influenza, having normal imaging results, and showing clinical improvement, the inclination was to still proceed with a lumbar puncture due to the concern for meningitis. The lumbar puncture results showed normal cerebrospinal fluid (CSF) cell counts with zero white and red blood cells, normal protein and glucose levels, and a negative biofire test, ruling out bacterial meningitis.
Outcome
The patient was discharged from the emergency department with a prescription for Tamiflu and instructions to follow up with their primary care provider.
This case underscores the complexity of managing pediatric patients with potential neurological symptoms and highlights the importance of a cautious, yet thorough approach to diagnostic evaluations.
The literature suggests that a well-appearing febrile infant with a bulging fontanelle does not have bacterial meningitis: https://pubmed.ncbi.nlm.nih.gov/19531528/
Although 27% of the 153 included infants had CSF pleocytosis, only 1 had bacterial meningitis: “The history of the infant with bacterial meningitis was positive for vomiting and restlessness. In her physical examination she was described as septic looking and lethargic. Her blood count revealed leucopenia (1.46103/mm3) and neutropenia. CSF culture was positive for Streptococcus pneumoniae.” Of note, none of the febrile infants with bulging fontanelle who appeared well had bacterial meningitis.
The key is making a determination that the infant is well-appearing, which is hard when they are febrile and have stranger anxiety and it’s the middle of the night. Sometimes, a tincture of time (and antipyretics!) are key — if they remain irritable/inconsolable after defervescence, then LP.