Bilateral generalized polymicrogyria

Alternate names

Bilateral generalised polymicrogyria

Definition

Bilateral generalized polymicrogyria is a rare neurological disorder that affects the cerebral cortex (the outer surface of the brain). This is the most widespread form of polymicrogyria and typically affects the entire surface of the brain.

Cause

While the exact cause of bilateral generalized polymicrogyria is not fully understood, it is thought to be due to improper brain development during embryonic growth.

Inheritance

Autosomal recessive inheritance, a 25% chance

Most cases appear to follow an autosomal recessive pattern of inheritance.

Signs and symptoms

Signs and symptoms include severe intellectual disability, problems with movement, and seizures that are difficult or impossible to treat.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Delayed ability to walk
• Profound global developmental delay

30%-79% of people have these symptoms

• Cerebral visual impairment
• Intellectual disability, severe(Early and severe mental retardation)
• Muscular hypotonia of the trunk(Low muscle tone in trunk)
• Mutism(Inability to speak)
• Spastic tetraplegia
• Stereotypy(Repetitive movements)

5%-29% of people have these symptoms

• Atonic seizure
• Autistic behavior
• Bilateral tonic-clonic seizure(Grand mal seizures)
• Diffuse white matter abnormalities
• Dilation of lateral ventricles
• Dyskinesia(Disorder of involuntary muscle movements)
• Eyelid myoclonus
• Focal emotional seizure with laughing
• Focal motor seizure
• Gastroesophageal reflux(Acid reflux)
• Generalized myoclonic seizure
• Generalized tonic seizure(Hypoplasia of the corpus callosum)(Underdevelopment of part of brain called corpus callosum)
• Hypoplastic hippocampus(Small hippocampus)
• Impaired mastication(Chewing difficulties)
• Infantile spasms
• Intellectual disability, mild(Mental retardation, borderline-mild)
• Intellectual disability, moderate(IQ between 34 and 49)
• Intellectual disability, profound(IQ less than 20)
• Microcephaly(Abnormally small skull)
• Nasogastric tube feeding
• Oculogyric crisis
• Oral-pharyngeal dysphagia
• Paroxysmal dyskinesia
• Self-injurious behavior(Self-injurious behaviour)
• Severe global developmental delay
• Short stature(Decreased body height)
• Sleep disturbance(Difficulty sleeping)
• Status epilepticus(Repeated seizures without recovery between them)
• Total ophthalmoplegia
• Typical absence seizure
• Widened subarachnoid space

Diagnosis

• The diagnosis of PMG is typically made by MRI since computed tomography (CT) and other imaging methods do not have high enough resolution or adequate contrast to identify the small folds that define PMG.
• In 5% of cases, PMG is detected on prenatal ultrasound examination by the presence of abnormalities – usually microcephaly and/or associated brain malformations.[1].

Treatment

Treatment is based on the signs and symptoms present in each person.

NIH genetic and rare disease info

• NIH info on Bilateral generalized polymicrogyria

Bilateral generalized polymicrogyria is a rare disease.