Hemimegalencephaly: Difference between revisions

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{{Infobox medical condition (new)
{{Short description|A rare neurological condition characterized by the enlargement of one hemisphere of the brain}}
| name            = Hemimegalencephaly
| synonyms        =
| image          = OJO-7-43-g005.jpg
|alt=
| caption        = Left-sided hemimegalencephaly.
|image_size=
| pronounce      =
| field          =
| symptoms        =Frequent seizures often resistant to medicine
| complications  =
| onset          =Congenital
| duration        =Long term
| types          =
| causes          =
| risks          =
| diagnosis      =
| differential    =
| prevention      =
| treatment      =Hemispherectomy
| medication      =Anti-epileptic drugs
| prognosis      =
| frequency      =
| deaths          =
}}


'''Hemimegalencephaly''' ('''HME'''), or unilateral [[megalencephaly]], is a [[Rare disease|rare]] [[congenital disorder]] affecting all or a part of a cerebral hemisphere.<ref name="pmid17416820">{{cite journal|last1=Sato|first1=N|last2=Yagishita|first2=A|last3=Oba|first3=H|last4=Miki|first4=Y|last5=Nakata|first5=Y|last6=Yamashita|first6=F|last7=Nemoto|first7=K|last8=Sugai|first8=K|last9=Sasaki|first9=M|title=Hemimegalencephaly: a study of abnormalities occurring outside the involved hemisphere.|journal=AJNR. American Journal of Neuroradiology|date=April 2007|volume=28|issue=4|pages=678–82|pmid=17416820|url=http://www.ajnr.org/content/28/4/678}}</ref> It causes severe seizures, which are often frequent and hard to control. A minority might have seizure control with medicines, but most will need [[Hemispherectomy|removal or disconnection of the affected hemisphere]] as the best chance. Uncontrolled, they often cause progressive intellectual disability and brain damage and stop development.<ref>{{Cite web|url=https://www.brainrecoveryproject.org/for-parents/when-to-ask-for-a-surgical-evaluation/your-child-has-a-likely-drug-resistant-condition/hemimegalencephaly/|title=Hemimegalencephaly - Why hemispherectomy is usually required|website=www.brainrecoveryproject.org|language=en-US|access-date=2018-04-12}}</ref>
'''Hemimegalencephaly''' is a rare [[neurological disorder]] characterized by the abnormal enlargement of one hemisphere of the [[brain]]. This condition is a type of [[cortical dysplasia]], which involves abnormal development of the [[cerebral cortex]]. Hemimegalencephaly can lead to a variety of neurological symptoms, including [[seizures]], developmental delays, and [[hemiparesis]].


== Symptoms ==
==Pathophysiology==
Seizures are the main symptom. There can be as many as hundreds of seizures a day.<ref name=":0">{{Cite web|url=https://health.ucsd.edu/news/releases/Pages/2012-25-hemimegalencephaly.aspx|title=Gene Mutations Cause Massive Brain Asymmetry|website=UC Health - UC San Diego|language=en-US|access-date=2018-04-12}}</ref> Seizures usually begin days right after birth, though they can be delayed by months or, rarely, start in early childhood.<ref name=":2">{{Cite web|url=http://hemifoundation.homestead.com/hemimegalencephaly.html|title=Hemimegalencephaly & Cortical Dysplasia|website=hemifoundation.homestead.com|access-date=2018-04-14}}</ref>
Hemimegalencephaly results from a disruption in the normal development of the brain during [[embryogenesis]]. The exact cause of this disruption is not fully understood, but it is believed to involve genetic mutations that affect cell proliferation and differentiation. The overgrowth of one hemisphere leads to an imbalance in brain structure and function.


=== Other symptoms ===
The affected hemisphere may exhibit increased [[neuronal]] size, abnormal [[gyral]] patterns, and disorganized cortical layers. These structural abnormalities can disrupt normal [[neural networks]], leading to the clinical manifestations of the disorder.


* Asymmetrical or enlarged head<ref name=":2" />
==Clinical Presentation==
* Developmental delay<ref name=":2" />
The symptoms of hemimegalencephaly can vary widely depending on the extent and location of the brain abnormalities. Common clinical features include:
* Progressive weakness of half the body<ref name=":2" />
* Progressive blindness of half the body<ref name=":2" />


==Genetics==
* '''Seizures''': Often the first symptom to appear, seizures in hemimegalencephaly can be difficult to control with medication. They may present as [[infantile spasms]], [[focal seizures]], or generalized seizures.
Somatic activation of ''[[AKT3]]'' causes hemispheric developmental brain malformations.<ref name="pmid22500628">{{cite journal|last1=Poduri|first1=Annapurna|last2=Evrony|first2=Gilad D.|last3=Cai|first3=Xuyu|last4=Elhosary|first4=Princess Christina|last5=Beroukhim|first5=Rameen|last6=Lehtinen|first6=Maria K.|last7=Hills|first7=L. Benjamin|last8=Heinzen|first8=Erin L.|last9=Hill|first9=Anthony|last10=Hill|first10=R. Sean|last11=Barry|first11=Brenda J.|last12=Bourgeois|first12=Blaise F.D.|last13=Riviello|first13=James J.|last14=Barkovich|first14=A. James|last15=Black|first15=Peter M.|last16=Ligon|first16=Keith L.|last17=Walsh|first17=Christopher A.|title=Somatic Activation of AKT3 Causes Hemispheric Developmental Brain Malformations|journal=Neuron|date=April 2012|volume=74|issue=1|pages=41–48|doi=10.1016/j.neuron.2012.03.010|pmid=22500628|pmc=3460551}}</ref>
* '''Developmental Delay''': Children with hemimegalencephaly often experience delays in reaching developmental milestones, such as sitting, walking, and talking.
==Pathophysiology==
* '''Hemiparesis''': Weakness or paralysis on one side of the body may occur, corresponding to the affected hemisphere.
It is a disorder related to excessive neuronal proliferation and [[hamartomatous]] overgrowth affecting the [[Cerebral cortex|cortical]] formation.<ref name="pmid18687750">{{cite journal|last1=Abdel Razek|first1=A.A.K.|last2=Kandell|first2=A.Y.|last3=Elsorogy|first3=L.G.|last4=Elmongy|first4=A.|last5=Basett|first5=A.A.|title=Disorders of Cortical Formation: MR Imaging Features|journal=American Journal of Neuroradiology|date=7 August 2008|volume=30|issue=1|pages=4–11|doi=10.3174/ajnr.A1223|pmid=18687750}}</ref> The excessive proliferation is postulated to occur early and to possibly continue beyond the normal proliferative period. [[Epidermal growth factor]] is thought to play an important role in the excessive proliferation and the pathogenesis of HME.<ref name="SarnatCuratolo2007">{{cite book|author1=Harvey B. Sarnat|author2=Paolo Curatolo|title=Malformations of the Nervous System|url=https://books.google.com/books?id=XzwNPUW2ucgC&pg=PA154|date=26 September 2007|publisher=Newnes|isbn=978-0-08-055984-1|pages=154}}</ref>
* '''Intellectual Disability''': Cognitive impairment is common, with varying degrees of severity.


==Diagnosis==
==Diagnosis==
It should be suspected in infants or children with intractable, frequent seizures.<ref name=":0" /> On a [[CT scan]], the affected part is distorted and enlarged.<ref>{{Cite web|url=http://www.latimes.com/health/la-me-dylan-html-htmlstory.html|title=Radical surgery offers hope for baby racked by seizures|last=Hennessy-Fiske|first=Molly|website=latimes.com|access-date=2018-04-12|date=2012-06-15}}</ref> It can be diagnosed prenatally, but a lot of cases go undiagnosed until seizures begin. [[Ultrasound]] can display asymmetrical brain hemispheres.<ref name=":2" />
The diagnosis of hemimegalencephaly is typically made through a combination of clinical evaluation and [[neuroimaging]] studies. [[Magnetic resonance imaging]] (MRI) is the preferred imaging modality, as it provides detailed information about the structure of the brain. MRI findings in hemimegalencephaly include asymmetrical enlargement of one hemisphere, abnormal cortical thickening, and disorganized white matter.


==Treatment==
==Management==
Although there have been a few reports of medical treatment, the main treatment is radical: [[Hemispherectomy|remove or disconnect the affected side]]. However, it has a high mortality, and there have been reports of a [[vegetative state]] and seizures resuming, this time in the healthy hemisphere.<ref name=":1">{{Cite journal|last=Bonioli|first=Eugenio|last2=Palmieri|first2=Antonella|last3=Bellini|first3=Carlo|date=1994-03-01|title=Surgical vs. medical treatment of seizures in hemimegalencephaly|url=http://www.brainanddevelopment.com/article/0387-7604(94)90060-4/fulltext|journal=Brain and Development|language=English|volume=16|issue=2|pages=169|doi=10.1016/0387-7604(94)90060-4|issn=0387-7604}}</ref>
Management of hemimegalencephaly is primarily symptomatic and supportive. Treatment options include:


Surgery should be done as early as possible to minimize damage caused by seizures. However, a trial with drugs can be attempted for a few months before surgery, and there is a slim chance of it succeeding.<ref name=":1" /> The earlier surgery be done, the more the remaining side will do the missing side's job.
* '''Antiepileptic Drugs (AEDs)''': Used to control seizures, although they may be less effective in this condition.
* '''Surgical Intervention''': In cases where seizures are refractory to medication, surgical options such as [[hemispherectomy]] or [[hemispherotomy]] may be considered to remove or disconnect the affected hemisphere.
* '''Rehabilitation Therapies''': Physical, occupational, and speech therapy can help improve motor skills, communication, and overall development.


[[Benzodiazepines]] might control the seizures.<ref>{{Cite web|url=https://www.semanticscholar.org/paper/Hemimegalencephaly:-diagnosis-and-treatment.-Trounce-Rutter/59b1fdabd600d89d1c76b727f8ecc33d9c0f9a18|title=Hemimegalencephaly: diagnosis and treatment. - Semantic Scholar|access-date=2018-04-12|year=1991}}</ref>
==Prognosis==
The prognosis for individuals with hemimegalencephaly varies depending on the severity of the condition and the effectiveness of treatment. Early intervention and comprehensive management can improve outcomes, but many individuals will continue to experience significant neurological challenges throughout their lives.


==References==
==Related Pages==
{{Reflist}}
* [[Cortical dysplasia]]
== External links ==
* [[Seizure disorder]]
{{Medical resources
* [[Neurodevelopmental disorder]]
|  ICD10          = {{ICD10|Q|04|5|}}
* [[Hemispherectomy]]
|  ICD9          = 
|  ICDO          =
|  OMIM          =
|  OMIM_mult      =
|  MedlinePlus    =
|  eMedicineSubj  =
|  eMedicineTopic =
|  DiseasesDB    = 
|  MeSH          = D065705
|  Orphanet      = 99802
}}
{{Congenital malformations and deformations of nervous system}}
{{Multiple abnormalities}}


[[Category:Congenital disorders of nervous system]]
[[Category:Neurological disorders]]
[[Category:Neurological disorders]]
[[Category:Congenital disorders]]
[[Category:Rare diseases]]
[[Category:Rare diseases]]
[[Category:Syndromes affecting the nervous system]]
<gallery>
File:OJO-7-43-g005.jpg|Hemimegalencephaly
</gallery>

Revision as of 19:18, 22 March 2025

A rare neurological condition characterized by the enlargement of one hemisphere of the brain


Hemimegalencephaly is a rare neurological disorder characterized by the abnormal enlargement of one hemisphere of the brain. This condition is a type of cortical dysplasia, which involves abnormal development of the cerebral cortex. Hemimegalencephaly can lead to a variety of neurological symptoms, including seizures, developmental delays, and hemiparesis.

Pathophysiology

Hemimegalencephaly results from a disruption in the normal development of the brain during embryogenesis. The exact cause of this disruption is not fully understood, but it is believed to involve genetic mutations that affect cell proliferation and differentiation. The overgrowth of one hemisphere leads to an imbalance in brain structure and function.

The affected hemisphere may exhibit increased neuronal size, abnormal gyral patterns, and disorganized cortical layers. These structural abnormalities can disrupt normal neural networks, leading to the clinical manifestations of the disorder.

Clinical Presentation

The symptoms of hemimegalencephaly can vary widely depending on the extent and location of the brain abnormalities. Common clinical features include:

  • Seizures: Often the first symptom to appear, seizures in hemimegalencephaly can be difficult to control with medication. They may present as infantile spasms, focal seizures, or generalized seizures.
  • Developmental Delay: Children with hemimegalencephaly often experience delays in reaching developmental milestones, such as sitting, walking, and talking.
  • Hemiparesis: Weakness or paralysis on one side of the body may occur, corresponding to the affected hemisphere.
  • Intellectual Disability: Cognitive impairment is common, with varying degrees of severity.

Diagnosis

The diagnosis of hemimegalencephaly is typically made through a combination of clinical evaluation and neuroimaging studies. Magnetic resonance imaging (MRI) is the preferred imaging modality, as it provides detailed information about the structure of the brain. MRI findings in hemimegalencephaly include asymmetrical enlargement of one hemisphere, abnormal cortical thickening, and disorganized white matter.

Management

Management of hemimegalencephaly is primarily symptomatic and supportive. Treatment options include:

  • Antiepileptic Drugs (AEDs): Used to control seizures, although they may be less effective in this condition.
  • Surgical Intervention: In cases where seizures are refractory to medication, surgical options such as hemispherectomy or hemispherotomy may be considered to remove or disconnect the affected hemisphere.
  • Rehabilitation Therapies: Physical, occupational, and speech therapy can help improve motor skills, communication, and overall development.

Prognosis

The prognosis for individuals with hemimegalencephaly varies depending on the severity of the condition and the effectiveness of treatment. Early intervention and comprehensive management can improve outcomes, but many individuals will continue to experience significant neurological challenges throughout their lives.

Related Pages