Neural System - Abnormalities
|Embryology - 18 Feb 2019 Expand to Translate|
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- 1 Introduction
- 2 Some Recent Findings
- 3 Neural Tube Closure
- 4 Spina Bifida
- 5 Cephalic Disorders
- 6 Anencephaly
- 7 Holoprosencephaly
- 8 Hydrocephalus
- 9 Encephalocele
- 10 Encephalitis
- 11 Fragile X Syndrome
- 12 Autism
- 13 Rett Syndrome
- 14 Cerebral Palsy
- 15 Newborn Neural Exam
- 16 International Classification of Diseases
- 17 References
- 18 Glossary Links
There are many different congenital and environmentally derived abnormalities associated with the nervous system. There are potentially 1000's of neurological abnormalities that could be listed on this page, therefore this current page is only a very brief introduction to some of these neural abnormalities. For additional information see links at the bottom of each sub-heading. The latest ICD-11 coding now also includes a new category "LD90 Disorders of intellectual development".
As the nervous system continues to develop fetally and postnatally, environmental issues both before and after birth are relevant to neural development. Embryonic and fetal nutrition folate (required early for neural tube closure) and iodine (required later for neural growth and differentiation). The developmental environment can also impact upon neural growth; maternal drugs such as alcohol and heavy metals such as lead (mining, historically both petrol and paint). Finally, postnatally other sensory abnormalities (hearing) can also impact on achieving developmental milestones.
- Links: Low Folic Acid and NTDs
Some Recent Findings
|More recent papers|
This table allows an automated computer search of the external PubMed database using the listed "Search term" text link.
<pubmed limit=5>Abnormal Neural Development</pubmed>
Neural Tube Closure
Dysraphism is the term often used to describe the defective fusion of the neural folds. The position and degree of failure of fusion will result in either embryonic death or a range of different neural defects. The way (mode) in which the human neural tube fuses has been a source of contention. In humans, fusion appears to initiate at multiple sites along the neural groove, this mode of closure may differ from that found in many animal species used in developmental studies.
Human Embryonic Death:
- 5 weeks with total failure of fusion.
- 6.5 weeks with opening over the rhombencephalon.
- survive beyond 7 weeks with a defect at the frontal and parietal regions.
Mouse posterior neuropore Axd mutant
|Meningomyelocele||Spina Bifida Rates (USA Data)|
There are potentially many different causes of spina bifida and neural tube defects. The basis of the abnormality is a failure of the neural tube to close caudally. At least one known cause is a low maternal diet of folic acid (folate) containing foods. (see Neural Tube Defects and Low Folic Acid or Folic Acid below)
Neural tube defects from failure to close can be screened by amniocentesis or ultrasound.
Alpha-fetoproetin normally present in the CSF, leaks and can be detected in amniotic fluid.
|International Classification of Diseases ICD-11 LA02 Spina bifida|
|ICD-11 - LA02 Spina bifida
LA02.Y Other specified spina bifida
LA02.Z Spina bifida, unspecified
|ICD-10 - Q05 Spina bifida Incl.: hydromeningocele (spinal), meningocele (spinal), meningomyelocele, myelocele, myelomeningocele, rachischisis, spina bifida (aperta)(cystica), syringomyelocele Excl.: Arnold-Chiari syndrome (Q07.0), spina bifida occulta (Q76.0)
|Maternal nutrition||Alcohol use, Caffeine use, low folic acid, Low dietary quality, Elevated glycaemic load or index, Low methionine intake, Low serum choline level, Low serum vitamin B12 level, Low vitamin C level, Low zinc intake|
|Other maternal factors||smoking, maternal hyperthermia, Low socio-economic status, Maternal infections and illnesses (TORCH, viral infection, bacterial infection, fungal infection), maternal diabetes, Pregestational obesity, Psychosocial stress, Valproic acid use|
|Environmental factors||Ambient air pollution, Disinfectant by-products in drinking water, Indoor air pollution, Nitrate-related compounds, Organic solvents, Pesticides, Polycyclic aromatic hydrocarbons|
|Table data from review (see original review for references)|
Cephalic (Greek, kephale = head) are a large group of abnormalities that relate to both skeletal (skull) and neural (brain) associated defects including: anencephaly, hydrocephalus, encephalocele, colpocephaly (occipital horn enlargement), lissencephaly (smooth brain), porencephaly (cyst or cavity in cerebral hemisphere), acephaly (absence of head), exencephaly (brain outside skull), macrocephaly (large head), micrencephaly (small brain), otocephaly (absence of lower jaw), brachycephaly (premature fusion of coronal suture), oxycephaly (premature fusion of coronal suture + other), plagiocephaly (premature unilateral fusion of coronal or lambdoid sutures), scaphocephaly (premature fusion of sagittal suture), trigonocephaly.
A recent Spanish study has shown a concordance between a head circumference growth function and intellectual disability in relation with the cause of microcephaly.
- "3,269 head circumference (HC) charts of patients from a tertiary neuropediatric unit were reviewed and 136 microcephalic participants selected. Using the Z-scores of registered HC measurements we defined the variables: HC Minimum, HC Drop and HC Catch-up. We classified patients according to the presence or absence of intellectual disability (IQ below 71) and according to the cause of microcephaly (idiopathic, familial, syndromic, symptomatic and mixed). Using Discriminant Analysis a C-function was defined as C=HC Minimum + HC Drop with a cut-off level of C=-4.32 Z-score. In our sample 95% of patients scoring below this level, severe microcephaly, were classified in the disabled group while the overall concordance was 66%. In the symptomatic-mixed group the concordance between HC function and outcome reached 82% in contrast to only 54% in the idiopathic-syndromic group (P-value=0.0002)."
|International Classification of Diseases ICD-11 LA00 Anencephaly|
|ICD-11 LA00.0 Anencephaly or similar anomalies - "A malformation of the nervous system caused by the failure of neuropore closure. Infants are born with intact spinal cord, cerebellum, and brainstem, but lack formation of neural structures above this level. The skull is only partially formed but the eyes are usually normal."
LA00.Y Other specified anencephaly or similar anomalies
LA00.Z Anencephaly or similar anomalies, unspecified
|ICD-10 Q00 Anencephaly and similar malformations
|ventral view||lateral view|
Anencephaly in a fetus (GA week 18) from a diabetic mother. Ultrasound images (coronal) show a complete absence of the cranial vault and brain and enlarged orbits.
ICD-11 LA05 Cerebral structural developmental anomalies - LA05.2 Holoprosencephaly
ICD-10 Q04 Other congenital malformations of brain - Q04.2 Holoprosencephaly
Below are shown images of fetal holoprosencephaly and associated cyclopia.
|Human holoprosencephaly cyclopean dissection||Proboscis histology|
Hydrocephalus (historic image from Hess, 1922)
This is a defect of cerebrospinal fliud (CSF) flow, excess fluid production or impaired fluid absorption and can be congenital or acquired. Estimated incidence of 1 in 1000 live births the condition leads to enlarged ventricles and head, separated skull cranial sutures and fontanelles. Obstruction of CSF flow can occur at any time (prenatally or postnatally) and leads to accumulation of within the ventricles. The time of onset will have different effects and should be compared to the equilivant neurological events that are occuring.
Ventricular obstruction usually occurs at the level of the cerebral aqueduct (narrowest site), but can occur elsewhere, and can be caused by viral infection or zoonotic disease.
- Links: Congenital Hydrocephalus
Dandy Walker malformation
|Dandy Walker malformation (MRI) is another form of ventricular abnormality that affects cerebellar development.
The vermis of the cerebellum can be small or absent, the fourth ventricle enlarges due to cyst formation.
An ultrasound study of fetuses with Dandy-Walker malformation 13 to 16 weeks (GA 15-18 weeks) identified the fourth ventricle widely open posteriorly, even in the standard transcerebellar view, and the brainstem-vermis (BV) angle was > 45°, significantly increased compared to that in normal fetuses (P < 0.0001). Note that at this age, an open fourth ventricle can also found in about 10% of normal fetuses.
Named after Walter Dandy (1886 – 1946) and Arthur Earl Walker (1907 – 1995), two USA neurosurgeons.
- Links: Congenital Hydrocephalus
This defect is generally mesodermal in origin, leading to protrusion of brain and meninges outside the crainal cavity. The severity of the disorder can vary dependent upon the degree of mesodermal abnormality.
Normally a postnatal clinical syndrome of the central nervous system resulting in inflammation of the brain parenchyma and caused by a range of pathogens (viral, bacterial and protozoal infections). This infectious disease is due mainly to viral pathogens: Herpes simplex encephalitis 10%–20% of cases, Murray Valley encephalitis virus, Japanese encephalitis virus, Australian bat lyssavirus, West Nile virus, Hendra virus and Nipah virus. The pathogen is generally included in the specific encephalitis naming; Varicella encephalitis and Toxoplasma meningoencephalitis.
Fragile X Syndrome
Fragile X Syndrome (FXS) is the most common form of inherited mental retardation and autism. The condition is caused by a loss of the functional fragile X mental retardation protein (FMRP) an RNA-binding protein that can regulate the translation of specific mRNAs. There are several suggested additional roles for this protein including synaptic development and function and in adult neurogenesis.
- Links: Fragile X Syndrome
Autism (autism spectrum disorder, ASD) is a behaviourally defined brain disorder in children. Features include: impoverished verbal and non-verbal communication skills, reduced social interactions (bias their attention towards objects rather than the surrounding social situation), behavioural impairments in attention engagement/disengagement, poor emotional discrimination and facial recognition, and fail to response to their own names. There exist many different and unproven claims as to the origins of autism.
Developmentally associated with neural maturation changes in cortical thickness and organization, and particularly affecting pyramidal neurons. A rat model shows structural and behavioural features of autism as a result of altering the trajectory of early postnatal cortical development.
- Links: Neural Exam Movies
(RTT) A severe neurodevelopment disorder, with intellectual disability and abnormalities of movement, mainly caused by mutations in the X-linked (Xq28) Methyl-CpG-binding protein 2 (MECP2) gene and therefore almost exclusively in females. The congenital variant of Rett syndrome is caused by heterozygous mutation in the FOXG1 gene on chromosome 14q13.
|International Classification of Diseases ICD-11 Cerebral palsy|
|ICD-11 08 Diseases of the nervous system
|ICD-10 G80 Cerebral palsy|
Cerebral palsy is a group of disorders in motor impairment that limits activity, and is attributed to non-progressive disturbances during brain development in fetuses or infants (3-4 / 1,000).
Represented by one or more of these features:
- impaired cognition
- impaired communication
- impaired sensory perception
- behavioural abnormalities
- seizure disorders
- Links: Neural Exam Movies | Medline Plus | NINDS - Info | CDC Screening and Diagnosis | Cerebral Palsy Alliance
Newborn Neural Exam
Neural - The collapsed tables below link to a number of short videos that demonstrate simple assessments of the postnatal developing nervous system.
International Classification of Diseases
The International Classification of Diseases (ICD) World Health Organization's classification used worldwide as the standard diagnostic tool for epidemiology, health management and clinical purposes. This includes the analysis of the general health situation of population groups. It is used to monitor the incidence and prevalence of diseases and other health problems.
ICD-11 Structural developmental anomalies of the nervous system
- LA00 Anencephaly or similar anomalies
- LA01 Cephalocele
- LA02 Spina bifida
- LA03 Arnold-Chiari malformation type II
- LA04 Congenital hydrocephalus
- LA05 Cerebral structural developmental anomalies
- LA05.0 Microcephaly
- LA05.1 Megalencephaly
- LA05.2 Holoprosencephaly
- LA05.3 Corpus callosum agenesis
- LA05.4 Arhinencephaly
- LA05.5 Abnormal neuronal migration
- LA05.6 Encephaloclastic disorders
- LA05.7 Brain cystic malformations
- LA05.Y Other specified cerebral structural developmental anomalies
- LA05.Z Cerebral structural developmental anomalies, unspecified
- LA06 Cerebellar structural developmental anomalies
- LA07 Structural developmental anomalies of the neurenteric canal, spinal cord or vertebral column
- LA0Y Other specified structural developmental anomalies of the nervous system
- LA0Z Structural developmental anomalies of the nervous system, unspecified
|ICD-11 Conditions with disorders of intellectual development as a relevant clinical feature|
|LD90 Conditions with disorders of intellectual development as a relevant clinical feature
|LD9Y Other specified developmental anomalies
LD9Z Developmental anomalies, unspecified
|International Classification of Diseases ICD-11 20 Developmental anomalies (beta draft)|
|ICD-11 Beta Draft - NOT FINAL, updated on a daily basis, It is not approved by WHO, NOT TO BE USED for CODING except for agreed FIELD TRIALS.
Chapter 20 Developmental anomalies, only a few examples of the draft ICD-11 Beta coding and tree structure for "structural developmental anomalies" within this section are shown in the table below.
|Mortality and Morbidity Statistics - 20 Developmental Anomalies|
|Structural Developmental Anomalies
|Multiple developmental anomalies or syndromes|
|Chromosomal anomalies, excluding gene mutations|
|Conditions with disorders of intellectual development as a relevant clinical feature|
|LD6Y Other specified developmental anomalies
LD6Z Developmental anomalies, unspecified
|CD-11 Beta Draft - NOT FINAL, updated on a daily basis, It is not approved by WHO, NOT TO BE USED for CODING except for agreed FIELD TRIALS.|
|ICD-10 Congenital malformations of the nervous system (Q00-Q07)|
|Q00 Anencephaly and similar malformations
Q01 Encephalocele Incl.: encephalomyelocele, hydroencephalocele, hydromeningocele, cranial meningocele, cerebral meningoencephalocele Excl.: Meckel-Gruber syndrome (Q61.9)
Q02 Microcephaly Incl.: Hydromicrocephaly Micrencephalon Excl.: Meckel-Gruber syndrome (Q61.9)
Q04 Other congenital malformations of brain Excl.: cyclopia (Q87.0) macrocephaly (Q75.3)
Q05 Spina bifida - Incl.: hydromeningocele (spinal), meningocele (spinal), meningomyelocele, myelocele, myelomeningocele, rachischisis, spina bifida (aperta)(cystica), syringomyelocele Excl.: Arnold-Chiari syndrome (Q07.0), spina bifida occulta (Q76.0)
Q06 Other congenital malformations of spinal cord
Q07 Other congenital malformations of nervous system Excl.: familial dysautonomia [Riley-Day] (G90.1), neurofibromatosis (nonmalignant) (Q85.0)
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Journal of Pediatric Neurosciences - is official publication of the Indian Society for Pediatric Neurosurgery.
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Cite this page: Hill, M.A. (2019, February 18) Embryology Neural System - Abnormalities. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Neural_System_-_Abnormalities
- © Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G