Macrocephaly, defined as a frontooccipital head circumference above the 97th percentile, can have a variety of causes. It can be differentiated into asymptomatic familial forms (so-called benign macrocephaly) and secondary forms resulting from hydrocephalus or other space-occupying intracranial processes such as tumors, hygroma or hematomas. Isolated thickening of the calvarium is rare. In most other cases megalencephaly of varying degree may be the cause, which in turn may also have various causes. After exclusion of the above-mentioned secondary causes, rare genetic diseases can be considered, such as lysosomal storage diseases; leukodystrophies, such as Alexander’s disease; metabolic disorders of organic or amino acids, such as glutaraciduria or Canavan disease; as well as other syndromic diseases, such as large growth syndromes. If the usual imaging procedures and/or metabolic examinations do not reveal a cause, a genetic examination using next generation sequencing (gene panel diagnostics) can help clarification, especially in the presence of a developmental disorder.
Orrù et al 2018, Am J of Roentgenol. 210:848 / Chitkara et al 2016, InnovAiT 10:1 / Klein et al. 2013, Autism Res. 6:51 / Williams et al 2008, Am J Hum Genet. 146A:2023