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Start free with EleplanBilateral polymicrogyria
ORPHA:268940Morphological anomaly
What it is
Bilateral polymicrogyria is a rare cerebral malformation due to abnormal neuronal migration defined as a cerebral cortex with many excessively small convolutions. It presents with developmental delay, intellectual disability, seizures and various neurological impairments and may be isolated or comprise a clinical feature of many genetic syndromes. It may also be associated with perinatal cytomegalovirus infection.
Key facts
- Age of onset
- Infancy, Neonatal
- Inheritance
- Autosomal recessive, X-linked dominant
- Classified as
- Morphological anomaly
Signs and symptoms
Common30–79%
21- Abnormal pyramidal sign
- Aplasia/Hypoplasia of the brainstem
- Aplasia/Hypoplasia of the cerebral white matter
- Cerebellar ataxia associated with quadrupedal gait
- Cerebellar atrophy
- Cognitive impairment
- Delayed speech and language development
- Dyslexia
- Esotropia
- Focal-onset seizure
- Functional motor deficit
- Global developmental delay
- Intellectual disability, mild
- Intellectual disability, moderate
- Language impairment
- Mental deterioration
- Motor delay
- Pseudobulbar signs
- Spastic hemiparesis
- Spastic tetraparesis
- Ventriculomegaly
These ranges are how often a sign appears across everyone diagnosed, not a prediction for one person — most people have some of these and not others. Orphanet also records findings that are specifically absent in this disease; those are in the data but not listed here.
Genes reported in subtypes
Orphanet records these genes on 4 more specific entries under this disorder, not on this entry itself:
A well-studied disease is usually split into subtypes, and the gene is curated on whichever one the evidence belongs to. Open a subtype to see which gene goes with it.
ICD-10 codes
ICD-10 has no distinct code for most rare diseases, so many are filed under the nearest available one. A shared code identifies the group, not this disease — the ORPHAcode above is what identifies it.
Related health topics
Reached through the ICD-10 categories this disease is filed under, so these describe the broader group rather than this disease specifically.
Cross-references
Orphadata Science: Free access data from Orphanet. © INSERM 1999. Data version 2026-06-23. Available under CC BY 4.0. This is a reference, not medical advice.
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