Table 2.

Aetiologies of hydrocephalus

	Frequency, n (%)
Post-haemorrhagic hydrocephalus of prematurity	103 (31.9%)
Neural tube defects Myelomeningocele Encephalocele	40 (12.4%) 36 (11.1%) 4 (1.2%)
Genetic hydrocephalus Craniofacial abnormality X-linked hydrocephalus Other genetic syndromes	45 (13.9%) 13 (4.0%) 6 (1.9%) 26 (8.0%)
Congenital hydrocephalus Aqueduct stenosis Brain cyst Blake’s pouch cyst: Interhemispheric arachnoid cyst Porencephalic cyst Posterior fossa arachnoid cyst Other congenital brain malformations	62 (19.2%) 17 (5.3%) 25 (7.7%) 4 (1.2%) 4 (1.2%) 4 (1.2%) 13 (4.0%) 20 (6.2%)
Others Term intraventricular haemorrhage Infection Brain tumour Haematoma Trauma Unknown	73 (22.6%) 29 (9.0%) 16 (5.0%) 14 (4.3%) 2 (0.6%) 2 (0.6%) 10 (3.1%)

Other genetic syndromes combined all infants who had a genetic diagnosis of hydrocephalus, or for whom the genetics team highly suspected a genetic aetiology, but the precise syndrome had yet to be identified at the time of the study. Examples included Joubert syndrome, CHARGE syndrome, Walker-Warburg syndrome, Aicardi syndrome, and Galloway-Mowat syndrome. Other congenital brain malformations were complex congenital malformations with no obvious genetic cause, including holoprosencephaly, hydranencephaly, hemimegalencephaly, schizencephaly, septo-optic dysplasia, and Dandy Walker malformation. Term IVH was treated as a separate entity to PHH of prematurity. The pathophysiology of the brain injury in these neonates is different from that in preterm IVH; there is no germinal matrix injury, no periventricular infarction, and brain development is at a later stage. Management was also different; if there was acute hydrocephalus, infants who suffered term IVH underwent external ventricular drainage rather than insertion of a VSGS or an access device. When necessary, they underwent VP shunt insertion as soon as the intraventricular blood resolved