What is the approach to managing an increase in head circumference (HC) in infants?

Management of Increased Head Circumference in Infants

The approach to managing increased head circumference (HC) in infants depends critically on distinguishing between benign familial megalencephaly and pathological causes, with serial measurements and clinical assessment guiding the need for neuroimaging and intervention. 1

Initial Clinical Assessment

Serial Measurement Protocol

• Obtain accurate HC measurements using a firm, non-stretchable measuring tape positioned above the eyebrows and ears, plotting values on WHO or CDC growth charts to confirm macrocephaly (>2 standard deviations above mean) 1, 2
• Review all previous HC measurements to determine growth trajectory, as serial measurements over time are more valuable than a single measurement for identifying abnormal patterns 1
• Monitor HC every 2-4 weeks if initial measurements are concerning, as growth velocity is more informative than absolute size 1

Critical Red Flags Requiring Urgent Evaluation

• Rapidly enlarging HC with increased splaying of cranial sutures 1
• Full, tense, or bulging anterior fontanel indicating elevated intracranial pressure 1
• Papilledema on fundoscopic examination 1
• Worsening apnea and bradycardia, lethargy, feeding intolerance, or vomiting 1
• Abnormal neurologic examination including altered consciousness, abnormal tone, persistent primitive reflexes, absent protective reflexes, or focal deficits 1

Differential Diagnosis Framework

Benign Familial Megalencephaly

• Stable growth trajectory following a higher percentile curve 1
• Normal neurologic examination 1
• Parental HC measurements often elevated 1
• No neuroimaging required if these criteria are met 1

Pathological Causes in Premature Infants

Posthemorrhagic Hydrocephalus (PHH)

For premature infants with intraventricular hemorrhage (IVH), the management algorithm differs significantly:

• Clinical decisions about intervention are based on history, physical examination, and serial cranial ultrasonography 3
• The traditional ultrasonographic threshold for intervention was ventricular index above Levene's 97th percentile for estimated gestational age + 4 mm 3
• Rapidly enlarging HC after IVH is an insensitive sign of hydrocephalus in premature infants, as ventricles may be enlarging slowly without clinical deterioration 4

Management Algorithm by Clinical Scenario

For Symptomatic Posthemorrhagic Hydrocephalus

Non-Surgical Temporizing Measures

• Acetazolamide and furosemide are NOT recommended, as randomized trials demonstrated increased mortality and neurological morbidity at 1 year without decreasing shunt need 3
• Serial lumbar punctures (LPs) are NOT routinely recommended to reduce shunt placement or prevent hydrocephalus progression (Level I evidence) 3
• However, early intervention with serial LPs (before ventricular index crosses 97th percentile + 4 mm) may reduce surgical intervention need in select cases, with only 16% eventually requiring permanent shunts versus 62% with late intervention 3
• Daily LPs can remove up to 10 ml of CSF if the lumbar subarachnoid space communicates with the ventricular system 3

Surgical Temporizing Measures

When serial LPs are inadequate to maintain clinical stability, surgical options include ventricular access devices (VADs), ventriculosubgaleal (VSG) shunts, external ventricular drains (EVDs), or lumbar punctures (Level II recommendation) 3

Key evidence-based distinctions:

• VSG shunts reduce the need for daily CSF aspiration compared with VADs 3
• VADs reduce morbidity and mortality compared with EVDs 3
• Ventricular puncture should be reserved for infants in extremis, as it increases risk of CSF infection and loculated hydrocephalus 3

For Non-Premature Infants with Increased HC

Neuroimaging Indications

Proceed with MRI (preferred over CT) if any of the following are present: 1

• Signs of symptomatic hydrocephalus
• Abnormal neurologic examination
• Papilledema or visual changes
• Disproportionate growth (HC increasing faster than weight/length)
• Concern for structural abnormality

Neuroimaging is NOT routinely indicated if: 1

• Benign familial megalencephaly is suspected
• Stable growth trajectory along a consistent percentile
• Normal neurologic examination
• No concerning features on history or physical examination

Developmental Surveillance

Essential Screening Components

• Screen for motor delays, regression of previously acquired skills, asymmetric motor development, or development of handedness before 18 months 1
• Assess for seizure history, as recurrent nonfebrile seizures may indicate underlying structural brain abnormalities 1
• Perform developmental surveillance at each visit to identify emerging concerns 1

Associated Conditions Requiring Monitoring

In infants with confirmed microcephaly (HC >2 SD below mean), common concomitant conditions include intellectual delay, epilepsy, cerebral palsy, language delay, strabismus, ophthalmologic disorders, and cardiac, renal, urinary tract, and skeletal anomalies 2

Follow-Up Strategy

Serial Monitoring Protocol

• Measure HC, weight, and length at each visit, plotting all three parameters to identify proportionate versus disproportionate growth patterns 1, 5
• Reassess immediately if clinical status changes, including new symptoms, developmental regression, or accelerating head growth 1
• Consider genetics or neurology referral if syndromic features are present, developmental delays emerge, or growth pattern remains concerning despite benign initial workup 1

Common Pitfalls to Avoid

• Do not assume benign structural variation without proper serial measurements and neurologic assessment 1
• Do not delay neuroimaging in the presence of red flags, even if family history suggests benign megalencephaly 1
• In premature infants with IVH, do not rely solely on HC measurements to diagnose progressive hydrocephalus, as rapid HC increase may occur 9-20 days after hemorrhage without clinical deterioration 4
• Do not use medications (acetazolamide/furosemide) for PHH management, as they worsen outcomes 3
• Variations in HC within the normal range (5th-95th percentile) do not correlate with neurodevelopmental outcomes at 2 years 6