Causes of severe learning difficulty
| Timing of insult | Aetiological factor | Examples |
|---|---|---|
| AEDs, antiepileptic drugs; CMV, cytomegalovirus; RTA, road traffic accident. | ||
| Prenatal | Chromosomal abnormalities (account for ∼50% cases) | Down syndrome (trisomy 21); Angelman syndrome (15q11.2–12) |
| Inborn errors of metabolism | Phenylketonuria; mucopolysaccharidoses | |
| Genetic disorders (including X linked) | Fragile X syndrome; Rett syndrome | |
| Intrauterine infection | Toxoplasma, CMV, rubella, herpes | |
| Intrauterine toxins | Alcohol; drugs—AEDs | |
| Recognisable syndromes (including neurocutaneous) | Tuberous sclerosis; Soto’s syndrome | |
| Cerebral malformations | Agyria-pachygyria; holoprosencephaly | |
| Others | Congenital hypothyroidism; Duchenne muscular dystrophy | |
| Perinatal | Birth asphyxia | |
| Neonatal meningo-encephalitis | ||
| Postnatal | Hypoxic ischaemic | Drowning, smothering |
| Infection | Meningitis, encephalitis | |
| Trauma | Non-accidental injury; RTA | |
| Epileptic encephalopathies | West syndrome; Lennox Gastaut syndrome | |