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Difficulty: MediumPediatric Neurologic Disorders

A 99-month-old boy is evaluated in the pediatric neurology clinic for a rapidly increasing head circumference. At his 66-month well-child visit, his head circumference was at the 85th85^{\text{th}} percentile, but it has now crossed lines to the 99th99^{\text{th}} percentile. His weight and length continue to track along the 50th50^{\text{th}} percentile. The parents are extremely anxious; they have been reading about hydrocephalus and are concerned that he has a severe neurological delay because he only babbles, can pull himself to a stand, but cannot walk independently. On physical examination, the infant is playful and alert. The anterior fontanelle is open, soft, and flat. There is no sunsetting of the eyes, and muscle tone and deep tendon reflexes are normal. An ultrasound of the head reveals normal ventricular size and prominent subarachnoid spaces. Which of the following statements regarding this patient's presentation and management are true? (Select all that apply)

  1. The clinical presentation and imaging findings indicate benign enlargement of the subarachnoid spaces.Answer
  2. The condition is typically self-limiting, and the head circumference growth usually stabilizes by age 22 to 33 years.Answer
  3. C
    The patient's inability to walk independently at 99 months represents a significant gross motor delay requiring intervention.
  4. D
    Empiric broad-spectrum intravenous antibiotics must be initiated immediately for presumed central nervous system infection.
  5. E
    Immediate neurosurgical placement of a ventriculoperitoneal shunt is indicated to prevent irreversible brain damage.

Answer

The correct statements are that the clinical presentation indicates benign enlargement of the subarachnoid spaces, and this condition is typically self-limiting and stabilizes by age 2 to 3 years.
The correct statements accurately describe benign enlargement of the subarachnoid spaces (BESS). BESS presents in infants with rapidly increasing head circumference (crossing percentiles) but normal developmental milestones and a reassuring neurologic examination (e.g., flat anterior fontanelle, absence of sunsetting eyes). A head ultrasound confirms the diagnosis by demonstrating widened subarachnoid spaces (typically bifrontal) alongside normal or only mildly enlarged ventricles. The condition is benign and self-limiting; the excess cerebrospinal fluid is gradually reabsorbed, and head growth typically stabilizes along a new, higher percentile curve by age 22 to 33 years. No medical or surgical intervention is necessary, and management relies on reassuring the parents and monitoring head circumference.

Step-by-Step Solution

1
Analyze the patient's clinical presentation and physical exam findings.
The patient has rapid head growth but maintains normal development, a playful demeanor, and a soft, flat fontanelle.
To differentiate a benign etiology for macrocephaly from pathological increased intracranial pressure or hydrocephalus.
2
Evaluate the head ultrasound findings.
The imaging shows normal ventricular size with prominent subarachnoid spaces.
To confirm the specific diagnosis of benign enlargement of the subarachnoid spaces (BESS).
3
Assess the patient's developmental milestones against standardized age expectations.
Pulling to a stand and babbling at 9 months of age are entirely appropriate and normal milestones.
To address the parents' concerns regarding potential developmental delay and rule out true neurological regression.

Key Concept

Benign enlargement of the subarachnoid spaces in infancy presents with macrocephaly, normal developmental milestones, and normal ventricles on imaging; it is self-limiting and requires only conservative management.
Estimated Time:1m 30s
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Topics

Pediatric Neurologic Disorders

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