Polymicrogyria
Encyclopedia
Polymicrogyria is a developmental
malformation of the human brain
characterized by an excessive number of small convolutions (gyri) on the surface of the brain. Either the whole surface (generalized) or parts of the surface (focal) can be affected.
in itself, nor does it describe the underlying etiology
or cause of the brain malformation.
Polymicrogyria may in fact be just one piece of a syndrome
of developmental abnormalities, because children born with it may suffer from a wide spectrum of other problems, including: global developmental disabilities, mild to severe mental retardation
, motor dysfunctions including speech
and swallowing
problems, respiratory
problems, and seizures. Though it is difficult to make a predictable prognosis
for children with the diagnosis of PMG, there are some generalized clinical findings according to the areas of the brain that are affected.
such as MRI and CT
, polymicrogyria is becoming more widely diagnosed. However, polymicrogyria is often misdiagnosed as pachygyria
or lissencephaly
, even by experienced radiologists, since the differences between these conditions can be difficult to see on an MRI or CT scan.
, a slightly thicker cortex
, neuronal heterotopia
and enlarged ventricles
. When many of these small folds are packed tightly together, PMG may resemble pachygyria
(a few "thick folds" - a mild form of lissencephaly
).
.
An association with the gene WDR62
has been identified.
Human development (biology)
Human development is the process of growing to maturity. In biological terms, this entails growth from a one-celled zygote to an adult human being.- Biological development:...
malformation of the human brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
characterized by an excessive number of small convolutions (gyri) on the surface of the brain. Either the whole surface (generalized) or parts of the surface (focal) can be affected.
Clinical presentation
The diagnosis of PMG is merely descriptive and is not a diseaseDisease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
in itself, nor does it describe the underlying etiology
Etiology
Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....
or cause of the brain malformation.
Polymicrogyria may in fact be just one piece of a syndrome
Syndrome
In medicine and psychology, a syndrome is the association of several clinically recognizable features, signs , symptoms , phenomena or characteristics that often occur together, so that the presence of one or more features alerts the physician to the possible presence of the others...
of developmental abnormalities, because children born with it may suffer from a wide spectrum of other problems, including: global developmental disabilities, mild to severe mental retardation
Mental retardation
Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors...
, motor dysfunctions including speech
Speech
Speech is the human faculty of speaking.It may also refer to:* Public speaking, the process of speaking to a group of people* Manner of articulation, how the body parts involved in making speech are manipulated...
and swallowing
Swallowing
Swallowing, known scientifically as deglutition, is the process in the human or animal body that makes something pass from the mouth, to the pharynx, and into the esophagus, while shutting the epiglottis. If this fails and the object goes through the trachea, then choking or pulmonary aspiration...
problems, respiratory
Respiratory system
The respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles...
problems, and seizures. Though it is difficult to make a predictable prognosis
Prognosis
Prognosis is a medical term to describe the likely outcome of an illness.When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because...
for children with the diagnosis of PMG, there are some generalized clinical findings according to the areas of the brain that are affected.
- Bilateral frontal polymicrogyria (BFP)-Cognitive and motor delay, spastic quadriparesis, epilepsy
- Bilateral frontoparietal polymicrogyria (BFPP)-Severe cognitive and motor delay, seizures, dysconjugate gaze, cerebellar dysfunction
- Bilateral perisylvian polymicrogyria (BPP)-Pseudobulbar signs, cognitive impairment, epilepsy, some with arthrogryposisArthrogryposisArthrogryposis, also known as Arthrogryposis Multiplex Congenita, is a rare congenital disorder that is characterized by multiple joint contractures and can include muscle weakness and fibrosis. It is a non-progressive disease...
and/or lower motor neuron disease - Bilateral parasagittal parieto-occipital polymicrogyria (BPPP)-Partial seizures, some with mental retardation
- Bilateral generalized polymicrogyria (BGP)-Cognitive and motor delay of variable severity, seizures
Diagnosis
With increased use of imaging techniquesMedical imaging
Medical imaging is the technique and process used to create images of the human body for clinical purposes or medical science...
such as MRI and CT
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
, polymicrogyria is becoming more widely diagnosed. However, polymicrogyria is often misdiagnosed as pachygyria
Pachygyria
Pachygyria is a congenital malformation of the cerebral hemisphere. It results in unusually thick convolutions of the cerebral cortex. Typically, children have developmental delay and seizures, the onset and severity depending on the severity of the cortical malformation...
or lissencephaly
Lissencephaly
Lissencephaly, which literally means smooth brain, is a rare brain formation disorder caused by defective neuronal migration during the 12th to 24th weeks of gestation, resulting in a lack of development of brain folds and grooves . It is a form of cephalic disorder...
, even by experienced radiologists, since the differences between these conditions can be difficult to see on an MRI or CT scan.
Pathology
Polymicrogyria is a disorder of neuronal migration resulting in structurally abnormal cerebral hemispheres. The Greek roots of the name describe its salient feature: many [poly] small [micro] gyri (convolutions in the surface of the brain). It is also characterized by shallow sulciSulcus (neuroanatomy)
In neuroanatomy, a sulcus is a depression or fissure in the surface of the brain.It surrounds the gyri, creating the characteristic appearance of the brain in humans and other large mammals....
, a slightly thicker cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
, neuronal heterotopia
Heterotopia (medicine)
In medicine, "heterotopia" refers to normal tissue present at an abnormal site or the displacement of an organ or part of an organ from its normal position. For example, gray matter heterotopia, the displacement of gray matter into the cerebral white matter or ventricles...
and enlarged ventricles
Ventricular system
The ventricular system is a set of structures containing cerebrospinal fluid in the brain. It is continuous with the central canal of the spinal cord.-Components:The system comprises four ventricles:* right and left lateral ventricles* third ventricle...
. When many of these small folds are packed tightly together, PMG may resemble pachygyria
Pachygyria
Pachygyria is a congenital malformation of the cerebral hemisphere. It results in unusually thick convolutions of the cerebral cortex. Typically, children have developmental delay and seizures, the onset and severity depending on the severity of the cortical malformation...
(a few "thick folds" - a mild form of lissencephaly
Lissencephaly
Lissencephaly, which literally means smooth brain, is a rare brain formation disorder caused by defective neuronal migration during the 12th to 24th weeks of gestation, resulting in a lack of development of brain folds and grooves . It is a form of cephalic disorder...
).
Etiology
Causes are genetic, viral or due to nutritional deficits during gestationGestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
.
An association with the gene WDR62
WDR62
WD repeat-containing protein 62 is a protein that in humans is encoded by the WDR62 gene. Mutations in the WDR62 gene cause of a wide spectrum of severe cerebral cortical malformations including microcephaly , pachygyria with cortical thickening as well as hypoplasia of the corpus callosum.-Further...
has been identified.
See also
- Bilateral frontoparietal polymicrogyria (genetic lesion)
- Augmentative and alternative communicationAugmentative and alternative communicationAugmentative and alternative communication is an umbrella term that encompasses the communication methods used to supplement or replace speech or writing for those with impairments in the production or comprehension of spoken or written language...
- Epilepsy Phenome/Genome ProjectEpilepsy Phenome/Genome ProjectThe Epilepsy Phenome/Genome Project is a government-funded study to identify genes that influence the development of epilepsy and genes that affect the response to treatment. The study involves 25 major epilepsy centers and more than 150 scientists and clinical staff around the United States,...
Further reading
- Schuyler's MonsterSchuyler's MonsterSchuyler's Monster: A Father's Journey with His Wordless Daughter is a book by Robert Rummel-Hudson. Rummel-Hudson began writing online in 1995 and also writes a parenting blog called Fighting Monsters with Rubber Swords; both book and blog concern the author's and his wife's parenting of their...
: A Father's Journey with His Wordless Daughter, Robert Rummel-Hudson, St. Martin's Press, 2008 (ISBN 978-0312372422) - Congenital Bilateral Perisylvian Syndrome - A Family Story