From the Guidelines
The medical term for an abnormally large head is macrocephaly, which is defined as an occipitofrontal circumference (OFC) exceeding the mean for age and gender by at least 2 SD, corresponding to the 97th percentile. This condition can be benign, such as familial macrocephaly, or may indicate underlying conditions like hydrocephalus, brain tumors, genetic disorders, or metabolic conditions 1. The diagnosis typically involves measuring head circumference and may require imaging studies like CT scans or MRI to determine the cause. According to the most recent guidelines, macrocephaly has a wide variety of causes besides megalencephaly, including hydrocephalus and increased skull thickness 1.
Key Points to Consider
- Macrocephaly is diagnosed when the head circumference measures larger than the 98th percentile for the person's age and sex.
- The condition can be benign or may indicate underlying conditions that require specific treatments.
- Imaging studies like CT scans or MRI may be necessary to determine the cause of macrocephaly.
- Regular monitoring is important, especially in children, to ensure normal brain development and function.
- The diagnosis and evaluation of macrocephaly involve measuring the head circumference and comparing it to standardized growth charts, with measurements consistently above the 98th percentile confirming the diagnosis 1.
Importance of Accurate Diagnosis
Accurate diagnosis of macrocephaly is crucial to identify the underlying cause and provide appropriate treatment. As noted in a study published in Nature Reviews Neurology, megalencephaly, which refers to an abnormally large brain size, can be caused by disruption of signaling pathways that regulate brain cellular proliferation, differentiation, cell cycle regulation, and survival 1. Therefore, a comprehensive diagnostic work-up, including imaging studies and genetic testing, may be necessary to determine the underlying cause of macrocephaly. The medical term for an abnormally large head, macrocephaly, is a critical diagnosis that requires careful evaluation and monitoring to ensure optimal outcomes.
From the Research
Definition of Macrocephaly
- Macrocephaly is defined as a head circumference above the 98th percentile or greater than +2SD above the mean for gestational age 2
- It can also be defined as an abnormally large head with an occipitofrontal circumference (OFC) >2 standard deviations (SD) above the mean for a given age and sex 3, 4
Types of Macrocephaly
- Primary macrocephaly: due to increased brain tissue (megalocephaly), which can be familial and benign or syndromic 2
- Secondary macrocephaly: due to various causes, including communicating or non-communicating hydrocephalus, cerebral edema, focal and pericerebral increased fluid collections, thickened calvarium, and brain tumors 2
- Megalencephaly: refers exclusively to brain overgrowth, exceeding twice the SD (3SD-"clinically relevant" megalencephaly) 3, 4
Diagnosis and Evaluation
- A detailed family and personal history, neuroimaging, and a careful clinical evaluation are crucial to reach the correct diagnosis 3, 4
- Neuroimaging plays an important role in the evaluation of macrocephaly, especially in the metabolic subtype which may not be overtly apparent clinically 4
- A clinicoradiological algorithm can be used to guide pediatricians in the assessment of children with macrocephaly 3, 4