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Difficulty: MediumPediatric Neurologic Disorders

A 6-month-old boy is brought to the pediatric clinic by his parents for a routine well-child visit. His parents express significant concern because the infant is not yet crawling and cannot pick up small objects with his thumb and index finger. He is currently able to roll in both directions, sit momentarily without support, and babble. Over the past three weeks, the parents have noted that he is increasingly irritable and has had multiple episodes of forceful vomiting, primarily occurring in the morning. He has no history of fever, trauma, or diarrhea.

Vital signs are temperature 37.1°C (98.8°F), heart rate 110/min, and respiratory rate 24/min. Weight is at the 50th percentile, and length is at the 45th percentile. Head circumference has increased from the 60th percentile at age 4 months to the 98th percentile currently. On physical examination, the anterior fontanelle is full and tense. Neurologic examination reveals downward deviation of the eyes with sclera visible above the iris. The remainder of the examination is unremarkable.

Which of the following is the most appropriate next step in the management of this patient?

  1. A
    Measurement of serum thyroid-stimulating hormone
  2. B
    Referral for a comprehensive developmental assessment
  3. Magnetic resonance imaging of the brainAnswer
  4. D
    Reassurance and routine follow-up in two months
  5. E
    Empiric administration of intravenous ceftriaxone

Answer

The correct answer is Magnetic resonance imaging of the brain.
The correct next step is Magnetic resonance imaging of the brain. The infant exhibits unequivocal signs of increased intracranial pressure, including rapidly expanding head circumference, a tense anterior fontanelle, and morning vomiting (a hallmark of increased ICP due to hypoventilation and elevated pCO2 during sleep). Additionally, the physical finding of downward gaze preference with visible sclera above the iris is known as the 'sun-setting' sign, which occurs due to pressure on the dorsal midbrain (Parinaud syndrome) secondary to hydrocephalus. Brain MRI is necessary to establish the exact cause of hydrocephalus before surgical intervention.

Step-by-Step Solution

1
Analyze the developmental milestones reported by the parents against expected age norms.
The infant's ability to roll, sit momentarily, and babble is normal for a 6-month-old. Crawling and pincer grasp are not expected until 8-9 months and 9-12 months, respectively.
Differentiating parental anxiety about normal development from true developmental delay prevents unnecessary referrals and misdiagnosis.
2
Evaluate the patient's acute physical findings and recent history.
The patient has rapidly progressive macrocephaly (crossing major percentiles), a tense fontanelle, morning vomiting, and sun-setting eyes.
These findings form the classic constellation of increased intracranial pressure (ICP), highly suspicious for hydrocephalus.
3
Determine the most appropriate immediate management for suspected hydrocephalus in an infant.
Definitive neuroimaging, such as a Magnetic resonance imaging (MRI) of the brain, is indicated.
Imaging is required to identify the etiology of the hydrocephalus (e.g., tumor, hemorrhage, congenital malformation) and to guide life-saving neurosurgical intervention.

Key Concept

Recognition of increased intracranial pressure in an infant and differentiating normal developmental milestones from true neurologic pathology.
Estimated Time:1m 30s
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Topics

Pediatric Neurologic Disorders

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