Version July 2025
| Early infantile (birth to 6 mo of age) | Hydrocephalus (progressive or "arrested") | |
| Induction disorders | Spina bifida cystica, cranium bifidum, Chiari malformations (types I, II, and III), aqueductal stenosis, holoprosencephaly | |
| Mass lesions | Neoplasms, atrioventricular malformations, congenital cysts | |
| Intrauterine infections | Toxoplasmosis, cytomegalic inclusion disease, syphilis, rubella | |
| Perinatal or postnatal infections | Bacterial, granulomatous, parasitic | |
| Perinatal or postnatal hemorrhage | Hypoxia, vascular malformation, trauma | |
| Hydranencephaly | ||
| Subdural effusion | ||
| Hemorrhagic, infectious, cystic hygroma | ||
| Normal variant (often familial) | ||
| Late infantile (6 mo to 2 yr of age) | Hydrocephalus (progressive or "arrested") | |
| Space-occupying lesions | Tumors, cysts, abscess | |
| Postbacterial or granulomatous meningitis | ||
| Posthemorrhagic | Trauma or vascular malformation | |
| Dandy-Walker syndrome | ||
| Subdural effusion | ||
| Increased intracranial pressure syndrome | ||
| Pseudotumor cerebri | Lead, tetracycline, hypoparathyroidism, corticosteroids, excess or deficiency of vitamin A, cyanotic congenital heart disease | |
| Primary skeletal cranial dysplasias (thickened or enlarged skull) | ||
| Osteogenesis imperfecta, hyperphosphatemia, osteopetrosis, rickets | ||
| Megalencephaly (increase in brain substance) | ||
| Metabolic central nervous system diseases | Leukodystrophies (eg, Canavan, Alexander), lipidoses (Tay-Sachs), histiocytosis, mucopolysaccharidoses | |
| Proliferative neurocutaneous syndromes | von Recklinghausen tuberous sclerosis, hemangiomatosis, Sturge-Weber | |
| Cerebral gigantism | Sotos syndrome | |
| Achondroplasia | ||
| Primary megalencephaly | May be familial and unassociated with abnormalities of cellular architecture, or associated with abnormalities of cellular architecture | |
| Early to late childhood (older than 2 yr of age) | Hydrocephalus (progressive or "arrested") | |
| Space-occupying lesions | ||
| Preexisting induction disorder | Aqueductal stenosis | |
| Postinfectious | ||
| Hemorrhagic | ||
| Chiari type I malformation | ||
| Megalencephaly | ||
| Proliferative neurocutaneous syndromes | ||
| Familial | ||
| Pseudotumor cerebri | ||
| Normal variant | ||
