Table 1

Causes of severe learning difficulty

Timing of insultAetiological factorExamples
AEDs, antiepileptic drugs; CMV, cytomegalovirus; RTA, road traffic accident.
PrenatalChromosomal abnormalities (account for ∼50% cases)Down syndrome (trisomy 21); Angelman syndrome (15q11.2–12)
Inborn errors of metabolismPhenylketonuria; mucopolysaccharidoses
Genetic disorders (including X linked)Fragile X syndrome; Rett syndrome
Intrauterine infectionToxoplasma, CMV, rubella, herpes
Intrauterine toxinsAlcohol; drugs—AEDs
Recognisable syndromes (including neurocutaneous)Tuberous sclerosis; Soto’s syndrome
Cerebral malformationsAgyria-pachygyria; holoprosencephaly
OthersCongenital hypothyroidism; Duchenne muscular dystrophy
PerinatalBirth asphyxia
Neonatal meningo-encephalitis
PostnatalHypoxic ischaemicDrowning, smothering
InfectionMeningitis, encephalitis
TraumaNon-accidental injury; RTA
Epileptic encephalopathiesWest syndrome; Lennox Gastaut syndrome