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Systematic Approach to Pediatric Macrocephaly
Jennifer Huang1, Asha Sarma1, Stephen Little1
1From the Department of Radiology, Vanderbilt University Medical Center, 1161 21st Ave S, Nashville, TN 37232 (J.H., A.S., S.P.); and Children's Healthcare of Atlanta, Emory University School of Medicine, Atlanta, Ga (S.L.).
Insights
Macrocephaly, or large head size, is common in children and often requires neuroimaging. A new classification system helps identify causes by examining cranial components like cerebrospinal fluid, brain tissue, or skull volume.
Area of Science:
- Pediatric Radiology
- Neurology
- Medical Imaging
Background:
- Macrocephaly (head circumference > 2 SD above mean) is a frequent pediatric finding, often prompting neuroimaging.
- The differential diagnosis is broad, with many conditions presenting differently in infants versus older children with fused skull sutures.
- The Monroe-Kellie hypothesis explains how intracranial volume changes lead to increased intracranial pressure when skull sutures are closed.
Purpose of the Study:
- To present a practical classification paradigm for evaluating pediatric macrocephaly.
- To highlight the role of various imaging modalities (US, CT, MRI) in diagnosing macrocephaly.
- To emphasize the importance of clinical context, patient age, and imaging findings in diagnosis.
Main Methods:
- Classification of macrocephaly based on the enlarged cranial component: cerebrospinal fluid, blood/vasculature, brain parenchyma, or calvarium.
- Review of common and rare causes of pediatric macrocephaly.
- Correlation of imaging findings with clinical presentation and age.
Main Results:
- Most pediatric macrocephaly cases involve increased cerebrospinal fluid spaces, such as benign enlargement of the subarachnoid space.
- Distinguishing benign conditions from traumatic subdural fluid collections is critical.
- Other causes include hydrocephalus (aqueductal web, hemorrhage, neoplasm) and rare overgrowth/metabolic disorders.
Conclusions:
- A systematic approach to classifying macrocephaly by cranial component aids diagnosis.
- Imaging plays a crucial role in identifying the underlying cause, guiding further management, and potentially prompting genetic testing.
- Accurate diagnosis is essential for differentiating benign conditions from serious pathologies and trauma.
Abstract:
Macrocephaly, defined as a head circumference greater than 2 standard deviations above the mean, is a relatively common presenting symptom in the pediatric population at routine well-child examinations and a common indication for neuroimaging. Multiple imaging modalities are complementary in evaluating macrocephaly, including US, CT, and MRI. The differential diagnosis for macrocephaly is broad, and many disease processes lead to macrocephaly only when the sutures are open. In patients with closed sutures, these entities instead lead to increased intracranial pressure, according to the Monroe-Kellie hypothesis, which states that there is an equilibrium between intracranial constituents due to the fixed intracranial volume. The authors describe a useful paradigm for classifying macrocephaly by identifying which of the four components of the cranium (ie, cerebrospinal fluid, blood and vasculature, brain parenchyma, or calvarium) has an increased volume. Patient age, additional imaging findings, and clinical symptoms are also useful features. Most cases in the pediatric population are due to increased cerebrospinal fluid spaces, such as benign enlargement of the subarachnoid space, which must be carefully distinguished from subdural fluid collections in patients with accidental or nonaccidental trauma. Other common causes of macrocephaly are discussed, including hydrocephalus secondary to an aqueductal web, hemorrhage, or a neoplasm. The authors also provide information on some of the rarer diseases for which imaging may provide the impetus for genetic testing (eg, overgrowth syndromes and metabolic disorders). ©RSNA, 2023 Quiz questions for this article are available through the Online Learning Center.
