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Disease Profile

Bilateral perisylvian polymicrogyria

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.


US Estimated

Europe Estimated

Age of onset





Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Perisylvian syndrome; Polymicrogyria, bilateral perisylvian; Congenital bilateral perisylvian syndrome;


Congenital and Genetic Diseases; Nervous System Diseases


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. 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.[1] Signs and symptoms typically become apparent at birth, infancy, or later during childhood, and may include partial paralysis of the face, tongue, jaw, and throat; problems with speech and swallowing; excessive drooling; and seizures. Mild to severe intellectual disability often is also present. Some people with BPP have other health problems or birth defects.[1][2][3][4] Most cases of BPP occur sporadically in people with no family history of BPP. Rarely, more than one family member has BPP, and the pattern of inheritance depends on the cause. Genetic causes may include mutations in single genes and contiguous gene disorders such as 22q11.2 deletion syndrome. BPP has also been reported in association with twin pregnancy complications.[1][3][5][6][7] The diagnosis of BPP is based on the symptoms present and a thorough neurological evaluation including various imaging techniques. Treatment aims to address individual symptoms present in each person.[1][4] For example, anti-seizure medications may help control seizures.[1] The quality of life and life expectancy for people with BPP are not well-described but may depend on severity of symptoms, whether complications develop, and whether other birth defects or an underlying syndrome are present.[3]


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:[1][2][3][4][6]

  • 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.[1][2]

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
80%-99% of people have these symptoms
Bilateral perisylvian polymicrogyria
30%-79% of people have these symptoms
Delayed speech and language development
Deficiency of speech development
Delayed language development
Delayed speech
Delayed speech acquisition
Delayed speech development
Impaired speech and language development
Impaired speech development
Language delay
Language delayed
Language development deficit
Late-onset speech development
Poor language development
Speech and language delay
Speech and language difficulties
Speech delay

[ more ]

Distal arthrogryposis
EEG with central focal spikes
EEG with parietal focal spikes
EEG with polyspike wave complexes
Global developmental delay
Increased reflexes
Infantile muscular hypotonia
Decreased muscle tone in infant
Intellectual disability
Mental deficiency
Mental retardation
Mental retardation, nonspecific

[ more ]

Language impairment
Perisylvian predominant thick cortex pachygyria
Specific learning disability
5%-29% of people have these symptoms
Abnormality of masticatory muscle
Cerebellar dysplasia
Cerebellar vermis hypoplasia
Choanal atresia
Blockage of the rear opening of the nasal cavity
Obstruction of the rear opening of the nasal cavity

[ more ]

Lack of coordination of movement
Ectopic posterior pituitary
EEG with frontal focal spikes
Facial diplegia
Feeding difficulties
Feeding problems
Poor feeding

[ more ]

Focal sensory seizure
Gastroesophageal reflux
Acid reflux
Acid reflux disease

[ more ]

Hearing impairment
Hearing defect

[ more ]

Infantile spasms
Intrauterine growth retardation
Prenatal growth deficiency
Prenatal growth retardation

[ more ]

Limb hypertonia
Increased muscle tone of arm or leg
Lower limb spasticity
Abnormally small skull
Decreased circumference of cranium
Decreased size of skull
Reduced head circumference
Small head circumference

[ more ]

Little lower jaw
Small jaw
Small lower jaw

[ more ]

Involuntary, rapid, rhythmic eye movements
Oromotor apraxia
Partial paralysis of legs
Pectus excavatum
Funnel chest
Protruding tongue
Prominent tongue
Tongue sticking out of mouth

[ more ]

Pseudobulbar paralysis
Spastic tetraplegia
Percent of people who have these symptoms is not available through HPO
Atypical absence seizure
Bilateral tonic-clonic seizure
Grand mal seizures
Cognitive impairment
Abnormality of cognition
Cognitive abnormality
Cognitive defects
Cognitive deficits
Intellectual impairment
Mental impairment

[ more ]

Reading disability
More grooves in brain
X-linked dominant inheritance


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).[4] 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.[6][7]

Contiguous gene disorders that have been associated with BPP include 22q11.2 deletion syndrome and 1p36 deletion syndrome.[4]

Single gene disorders that have been associated with BPP include:[4]

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.[4][8]


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:[1][4]

Testing Resources

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.


    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, antiseizure medications may be prescribed to control seizures. People with BPP may also benefit from physical therapy and/or speech therapy.[1]


    Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

    Organizations Supporting this Disease

      Learn more

      These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

      Where to Start

      • Genetics Home Reference (GHR) contains information on Bilateral perisylvian polymicrogyria. This website is maintained by the National Library of Medicine.
      • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

        In-Depth Information

        • GeneReviews provides current, expert-authored, peer-reviewed, full-text articles describing the application of genetic testing to the diagnosis, management, and genetic counseling of patients with specific inherited conditions.
        • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
        • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
        • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
        • PubMed is a searchable database of medical literature and lists journal articles that discuss Bilateral perisylvian polymicrogyria. Click on the link to view a sample search on this topic.


          1. Congenital Bilateral Perisylvian Syndrome. NORD. 2015; https://rarediseases.org/rare-diseases/congenital-bilateral-perisylvian-syndrome/.
          2. Kilinc O, Ekinci G, Demirkol E & Agan K. Bilateral agenesis of arcuate fasciculus demonstrated by fiber tractography in congenital bilateral perisylvian syndrome. Brain Dev. March 2015; 37(3):352-355. https://www.ncbi.nlm.nih.gov/pubmed/24852949.
          3. Stutterd CA, Leventer RJ. Polymicrogyria: a common and heterogeneous malformation of cortical development. Am J Med Genet C Semin Med Genet. June, 2014; 166C(2):227-239. https://onlinelibrary.wiley.com/doi/full/10.1002/ajmg.c.31399.
          4. Stutterd CA, Dobyns WB, Jansen A, Mirzaa G, Leventer RJ. Polymicrogyria Overview. GeneReviews. August 16, 2018; https://www.ncbi.nlm.nih.gov/books/NBK1329/.
          5. Guerrini R, Marini C. Genetic malformations of cortical development. Exp Brain Res. August, 2006; 173(2):322-333. https://www.ncbi.nlm.nih.gov/pubmed/16724181.
          6. Clark M, Neville BG. Familial and genetic associations in Worster-Drought syndrome and perisylvian disorders. Am J Med Genet A. January 1, 2008; 146A(1):35-42. https://www.ncbi.nlm.nih.gov/pubmed/17994559.
          7. Guerrini R, Filippi T. Topical Review: Neuronal Migration Disorders, Genetics, and Epileptogenesis. J Child Neurol. April, 2005; 20(4):287-299. https://journals.sagepub.com/doi/abs/10.1177/08830738050200040401.
          8. Polymicrogyria, Bilateral Perisylvian, Autosomal Recessive; BPPR. Online Mendelian Inheritance in Man (OMIM). April 22, 2014; https://www.omim.org/entry/615752.

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