Hemimegalencephaly

Editor-In-Chief: Prab R Tumpati, MD
Obesity, Sleep & Internal medicine
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Hemimegalencephaly
Synonyms	N/A
Pronounce	N/A
Specialty	N/A
Symptoms	Seizures, developmental delay, hemiparesis, macrocephaly
Complications	Intellectual disability, epilepsy, cerebral palsy
Onset	Congenital
Duration	Lifelong
Types	N/A
Causes	Genetic mutation
Risks	Family history of genetic disorders
Diagnosis	MRI, CT scan
Differential diagnosis	Focal cortical dysplasia, tuberous sclerosis complex, Sturge-Weber syndrome
Prevention	N/A
Treatment	Anticonvulsants, hemispherectomy, physical therapy
Medication	N/A
Prognosis	Variable, depends on severity and treatment
Frequency	Rare
Deaths	N/A

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.

See also

• Cortical dysplasia
• Seizure disorder
• Neurodevelopmental disorder
• Hemispherectomy