Macrocephaly

Macrocephaly is a condition in which the human head is abnormally large; this includes the scalp, the cranial bone, and the contents of the cranium. It may be pathological or benign, even a familial genetic characteristic.

Macrocephaly
An MRI of a patient with benign familial macrocephaly (male with head circumference > 60cm)
SpecialtyMedical genetics 

Causes

Many people with abnormally large heads or large skulls are healthy, but macrocephaly may be pathological. 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 may 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]

In research, cranial height or brain imaging may be used to determine intracranial volume more accurately.[1]

Diagnosis

Macrocephaly is customarily diagnosed if head circumference is greater than two standard deviations (SDs) above the mean.[6] 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.

See also

References
  1. 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. "Archived copy" (PDF). Archived from the original (PDF) on 2015-10-09. Retrieved 2015-05-04.CS1 maint: archived copy as title (link)
  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. International Schizophrenia Consortium (September 2008). "Rare chromosomal deletions and duplications increase risk of schizophrenia; The International Schizophrenia Consortium;". Nature. 455 (7210): 237–241. 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.
  6. Fenichel, Gerald M. (2009). Clinical Pediatric Neurology: A Signs and Symptoms Approach (6th ed.). Philadelphia, PA: Saunders/Elsevier. p. 369. ISBN 978-1416061854.
Classification
External resources
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