Bilateral perisylvian polymicrogyria

Alternate names

Perisylvian syndrome; Polymicrogyria, bilateral perisylvian; Congenital bilateral perisylvian syndrome; CBPS; Perisylvian syndrome, congenital bilateral; PMGX

Definition

Bilateral perisylvian polymicrogyria (BPP) is a rare neurological disorder that affects the cerebral cortex (the outer surface of the brain). BPP is a subtype of a broader condition known as polymicrogyria.

Summary

The cerebral cortex of the brain normally consists of several deep folds and grooves. In BPP, the grooves that develop during embryonic growth form improperly on both sides of the brain near the Sylvian fissure, resulting in an increased number of folds that are unusually small.

Cause

• There are multiple possible causes of bilateral perisylvian polymicrogyria (BPP), and the cause can vary from person to person.
• In some cases, the cause may not be known.
• Genetic causes may include a contiguous gene disorder (a disorder caused by the deletion of multiple adjacent genes) or a single gene disorder (a disorder caused by a mutation in one gene).
• BPP may also have non-genetic causes.
• It has been reported in association with complications in twin pregnancies, including twin–twin transfusion syndrome and intrauterine death of a co‐twin.
• It has additionally been reported in association with amniotic band syndrome.
• Contiguous gene disorders that have been associated with BPP include 22q11.2 deletion syndrome and 1p36 deletion syndrome.

Single gene disorders that have been associated with BPP include:

• MPPH syndrome - caused by a mutation in the AKT3, CCND2, or PIK3R2 genes
• Smith-Kingsmore syndrome - caused by a mutation in the MTOR gene
• MCAP syndrome - caused by mutations in the PIK3CA gene
• Lissencephaly - caused by a mutation in the TUBA1A gene
• Weaver syndrome - caused by a mutation in the EZH2 gene

Single genes in which mutations have been associated with BPP (but not necessarily a defined disorder or syndrome) include the EOMES, NEDD4L, and ADGRG1 genes

Inheritance

• In most cases, bilateral perisylvian polymicrogyria (BPP) occurs sporadically in people with no family history of BPP. Less commonly, BPP is inherited, and more than one family member may have BPP.
• The inheritance in each of these cases depends on the underlying cause of BPP and may be autosomal dominant, autosomal recessive, or X-linked.

Signs and symptoms

Signs and symptoms of bilateral perisylvian polymicrogyria (BPP) usually are apparent at birth or become apparent during infancy or childhood. The signs and symptoms, and severity, vary from person to person but may include:

• Partial paralysis of muscles on both sides of the face, tongue, jaw, and throat
• Sudden, involuntary spasms of facial muscles
• Excessive drooling
• Difficulty with sucking, chewing, and/or swallowing (dysphagia)
• Difficulty with speech (dysarthria)
• Seizures
• Mild spasticity of the limbs (spastic tetraplegia)
• Developmental delay or learning impairments
• Mild to severe intellectual disability
• Contractures present from birth (congenital)
• Various other health problems or birth defects may occur in people with BPP, depending on whether an underlying genetic disorder with additional associated symptoms is present.

Diagnosis

A diagnosis of bilateral perisylvian polymicrogyria (BPP) is typically based on a thorough physical examination, a detailed medical history, and a complete neurological evaluation, which may include tests such as:

• Magnetic resonance imaging (MRI) - a diagnosis of polymicrogyria is usually made by MRI because MRI typically can detect the small folds in the brain more effectively than other imaging techniques.
• Electroencephalography (EEG) - a test that measures electrical activity in the brain
• Computed tomography (CT) scanning
• Genetic testing - different types of genetic tests may be performed to determine if there is a genetic cause for the BPP.

Treatment

The characteristics of the brain that define bilateral perisylvian polymicrogyria (BPP) cannot be corrected, but there are treatments or therapies that aim to improve the signs and symptoms of BPP. For example, anti-seizure medications may be prescribed to control seizures. People with BPP may also benefit from physical therapy and/or speech therapy.

NIH genetic and rare disease info

• NIH info on Bilateral perisylvian polymicrogyria

Bilateral perisylvian polymicrogyria is a rare disease.

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