Macrocephaly

Macrocephaly

An MRI of a patient with benign familial macrocephaly (male with head circumference > 60cm)
Classification and external resources
Specialty medical genetics
ICD-10 Q75.3
ICD-9-CM 756.0
OMIM 248000
DiseasesDB 22519
MedlinePlus 003305
MeSH D058627

Macrocephaly is a condition in which the head is abnormally large (circumference 2.5 standard deviations above normal for weight and gender); this includes the scalp, the cranial bone, and the contents of the cranium.

Causes

Macrocephaly may be pathologic, but many people with an unusually large head and large skull are healthy. Pathologic macrocephaly may be due to megalencephaly (enlarged brain), hydrocephalus (water on the brain), cranial hyperostosis (bone overgrowth), and other conditions. Pathologic macrocephaly is called "syndromic" when it is associated with any other noteworthy condition, and "nonsyndromic" otherwise. Pathologic macrocephaly can be caused by congenital anatomic abnormalities, genetic conditions, or by environmental events.[1]

Many genetic conditions are associated with macrocephaly, including familial macrocephaly related to the holgate gene, autism, PTEN mutations such as Cowden disease, neurofibromatosis type 1, and tuberous sclerosis; overgrowth syndromes such as Sotos syndrome (cerebral gigantism), Weaver syndrome, Simpson-Golabi-Behmel syndrome (bulldog syndrome), and macrocephaly-capillary malformation (M-CMTC) syndrome; neurocardiofacial-cutaneous syndromes such as Noonan syndrome, Costello syndrome, Gorlin Syndrome,[2] (also known as Basal Cell Nevus Syndrome) and cardiofaciocutaneous syndrome; Fragile X syndrome; leukodystrophies (brain white matter degeneration) such as Alexander disease, Canavan disease, and megalencephalic leukoencephalopathy with subcortical cysts; and glutaric aciduria type 1 and D-2-hydroxyglutaric aciduria.[1]

At one end of the genetic spectrum, duplications of chromosomes have been found to be related to autism and macrocephaly; at the other end, deletions of chromosomes have been found to be related to schizophrenia and microcephaly.[3][4][5]

Environmental events associated with macrocephaly include infection, neonatal intraventricular hemorrhage (bleeding within the infant brain), subdural hematoma (bleeding beneath the outer lining of the brain), subdural effusion (collection of fluid beneath the outer lining of the brain), and arachnoid cysts (cysts on the brain surface).[1]

Diagnosis

Macrocephaly is customarily diagnosed if head circumference is greater than two standard deviations (SDs) above the mean. Relative macrocephaly occurs if the measure is less than two SDs above the mean, but is disproportionately above that when ethnicity and stature are considered. In research, cranial height or brain imaging is also used to determine intracranial volume more accurately.[1]

See also

References

  1. 1 2 3 4 Williams CA, Dagli A, Battaglia A (2008). "Genetic disorders associated with macrocephaly". Am J Med Genet A 146A (16): 2023–37. doi:10.1002/ajmg.a.32434. PMID 18629877.
  2. ↑ http://www.gorlinsyndrome.org/EduDocs/General/Nevoid%20Basal%20Cell%20Carcinoma%20Syndrome.pdf
  3. ↑ Crespi; et al. (2010). "Comparative genomics of autism and schizophrenia". PNAS 107: 1736–1741. doi:10.1073/pnas.0906080106. PMC 2868282. PMID 19955444.
  4. ↑ "Rare chromosomal deletions and duplications increase risk of schizophrenia; The International Schizophrenia Consortium;". Nature 455: 237–241. September 2008. doi:10.1038/nature07239. PMC 3912847. PMID 18668038.
  5. ↑ Dumas L., Sikela J.M. (2009). "DUF1220 Domains, Cognitive Disease, and Human Brain Evolution". Cold Spring Harb. Symp. Quant. Biol. 74: 375–82. doi:10.1101/sqb.2009.74.025. PMC 2902282. PMID 19850849.

External links

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