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Anencephaly is the absence of a major portion of the brain, skull, and scalp that occurs during embryonic development. It is a cephalic disorder that results from a neural tube defect that occurs when the rostral (head) end of the neural tube fails to close, usually between the 23rd and 26th day following conception. Strictly speaking, the Greek term translates as "without a brain", but it is accepted that children born with this disorder usually only lack a telencephalon, the largest part of the brain consisting mainly of the cerebral hemispheres, including the neocortex, which is responsible for cognition. The remaining structure is usually covered only by a thin layer of membrane—skin, bone, meninges, etc., are all lacking. With very few exceptions, infants with this disorder do not survive longer than a few hours or days after birth.
Microcephaly is a medical condition involving a smaller-than-normal head. Microcephaly may be present at birth or it may develop in the first few years of life. Brain development is often affected; people with this disorder often have an intellectual disability, poor motor function, poor speech, abnormal facial features, seizures and dwarfism.
Schizencephaly is a rare birth defect characterized by abnormal clefts lined with grey matter that form the ependyma of the cerebral ventricles to the pia mater. These clefts can occur bilaterally or unilaterally. Common clinical features of this malformation include epilepsy, motor deficits, and psychomotor retardation.
Macrocephaly is a condition in which circumference of the human head is abnormally large. It may be pathological or harmless, and can be a familial genetic characteristic. People diagnosed with macrocephaly will receive further medical tests to determine whether the syndrome is accompanied by particular disorders. Those with benign or familial macrocephaly are considered to have megalencephaly.
MASA syndrome is a rare X-linked recessive neurological disorder on the L1 disorder spectrum belonging in the group of hereditary spastic paraplegias a paraplegia known to increase stiffness spasticity in the lower limbs. This syndrome also has two other names, CRASH syndrome and Gareis-Mason syndrome.
Aicardi syndrome is a rare genetic malformation syndrome characterized by the partial or complete absence of a key structure in the brain called the corpus callosum, the presence of retinal lacunes, and epileptic seizures in the form of infantile spasms. Other malformations of the brain and skeleton may also occur. The syndrome includes intellectual disability that is usually severe or moderate. So far, the syndrome has only been diagnosed in girls and in boys with two X chromosomes.
Encephalocele is a neural tube defect characterized by sac-like protrusions of the brain and the membranes that cover it through openings in the skull. These defects are caused by failure of the neural tube to close completely during fetal development. Encephaloceles cause a groove down the middle of the skull, or between the forehead and nose, or on the back side of the skull. The severity of encephalocele varies, depending on its location.
Congenital muscular dystrophies are autosomal recessively-inherited muscle diseases. They are a group of heterogeneous disorders characterized by muscle weakness which is present at birth and the different changes on muscle biopsy that ranges from myopathic to overtly dystrophic due to the age at which the biopsy takes place.
Dubowitz syndrome is a rare genetic disorder characterized by microcephaly, stunted growth, and a receding chin. Symptoms vary among patients, but other characteristics include a soft, high-pitched voice, partial webbing of the fingers and toes, palate deformations, genital abnormalities, language difficulties, and an aversion to crowds. The pathogenesis of the disease is yet to be identified, and no medical tests can definitively diagnose the disease. The primary method of diagnosis is to identify facial phenotypes. Since it was first described in 1965 by English physician Victor Dubowitz, over 140 cases have been reported worldwide. Although the majority of cases have been reported from the United States, Germany, and Russia, the disorder appears to affect both genders and all ethnicities equally.
Fryns-Aftimos syndrome is a rare chromosomal condition and is associated with pachygyria, severe mental retardation, epilepsy and characteristic facial features. This syndrome is a malformation syndrome, characterized by numerous facial dysmorphias not limited to hypertelorism, iris or retinal coloboma, cleft lip, and congenital heart defects. This syndrome has been seen in 30 unrelated people. Characterized by a de novo mutation located on chromosome 7p22, there is typically no family history prior to onset. The severity of the disorder can be determined by the size of the deletion on 7p22, enveloping the ACTB gene and surrounding genes, which is consistent with a contiguous gene deletion syndrome. Confirming a diagnosis of Fryns-Aftimos syndrome typically consists of serial single-gene testing or multigene panel of genes of interest or exome sequencing.
Microlissencephaly (MLIS) is a rare congenital brain disorder that combines severe microcephaly with lissencephaly. Microlissencephaly is a heterogeneous disorder, i.e. it has many different causes and a variable clinical course. Microlissencephaly is a malformation of cortical development (MCD) that occurs due to failure of neuronal migration between the third and fifth month of gestation as well as stem cell population abnormalities. Numerous genes have been found to be associated with microlissencephaly, however, the pathophysiology is still not completely understood.
Strømme syndrome is a very rare autosomal recessive genetic condition characterised by intestinal atresia, eye abnormalities and microcephaly. The intestinal atresia is of the "apple-peel" type, in which the remaining intestine is twisted around its main artery. The front third of the eye is typically underdeveloped, and there is usually moderate developmental delay. Less common features include an atrial septal defect, increased muscle tone or skeletal abnormalities. Physical features may include short stature, large, low-set ears, a small jaw, a large mouth, epicanthic folds, or fine, sparse hair.
Achalasia microcephaly syndrome is a rare condition whereby achalasia in the oesophagus manifests alongside microcephaly and intellectual disability. This is a rare constellation of symptoms with a predicted familial trend.
Jaxon Emmett Buell was an American child known for being born missing about 80% of his brain due to microhydranencephaly. He surpassed doctors' expectations, who predicted he would not live to be one year old. He lived for five years. When he turned one year old, his parents began posting updates about him on social media, which gained attention.
Morse–Rawnsley–Sargent syndrome is an extraordinarily rare and deadly congenital malformation syndrome which affects the central nervous system during embryogenesis. It occurs before conception.
Infantile cerebral and cerebellar atrophy with postnatal progressive microcephaly is a rare hereditary autosomal recessive malformation syndrome of the central nervous system characterized by profound motor delays and intellectual disabilities, progressive microcephaly, hypertonia, spasticity, clonus and epilepsy. MRI findings include severe cerebellar and cerebral deterioration (atrophy) and impaired myelination. This condition is an example of consequences from the Founder effect, especially that of Jewish populations.
Hall-Riggs syndrome is a rare genetic disorder that causes neurological issues and birth defects. People with Hall-Riggs syndrome usually have skeletal dysplasia, facial deformities, and intellectual disabilities. Only 8 cases from 2 families worldwide have been described in medical literature. It is an autosomal recessive genetic disorder, meaning both parents must carry the gene in order for their offspring to be affected.
Severe intellectual disability-progressive spastic diplegia syndrome is a rare novel genetic disorder characterized by severe intellectual disabilities, ataxia, craniofacial dysmorphisms, and muscle spasticity. It is a type of autosomal dominant syndromic intellectual disability.
Keratosis follicularis-dwarfism-cerebral atrophy syndrome is a rare, presumably X-linked recessive genetic disorder characterized by keratosis follicularis, severe congenital proportionate dwarfism, and brain atrophy. Other less common findings include microcephaly, intellectual disability, alopecia, epilepsy, and inguinal hernias. It has only been described in 6 males from a 2-generation Mexican family.
References
- 1 2 Behunova, Jana; Zavadilikova, Eva; Bozoglu, Tarik M.; Gunduz, Aysegul; Tolun, Aslihan; Yalcinkaya, Cengiz (2010-01-01). "Familial microhydranencephaly, a family that does not map to 16p13.13-p12.2: relationship with hereditary fetal brain degeneration and fetal brain disruption sequence". Clinical Dysmorphology. 19 (3): 107–118. doi:10.1097/mcd.0b013e32833946e9. PMID 20375726. S2CID 30667255.
- ↑ "OMIM Entry - # 605013 - MICROHYDRANENCEPHALY; MHAC". omim.org. Retrieved 2015-09-26.
- ↑ Pawlowski, A. "Baby born with part of brain missing turns 2, reaches new milestones". TODAY.com. Retrieved 2017-09-04.
- ↑ Micolucci, Vic (2020-04-07). "Jaxon Buell, Florida 'miracle boy,' passes away at 5". WJXT. Retrieved 2020-04-17.
This article incorporates text from this source, which is in the public domain : "Microhydranencephaly". Genetic and Rare Diseases Information Center. National Institutes of Health. 11 April 2012. Retrieved 26 September 2015.
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