Table 2.

Definition and categorization of neurological injuries

Factor	Category (n = scans)
	None-mild injury	Severe injury
IVH (Ahmann et al. 1980; Volpe 1981)	Grade 0–2 (n = 159)	Grade 3–4 (n = 56 scans)
- Bleeding into the ventricles of the brain.
- Overall occurrence rate of approximately 15%.
- IVH occurs in 40% of premature neonates who weigh less than 1500 g.
VM (Perlman and Rollins 2000; Mehlhorn et al. 2017)	Grade 0–1 (n = 208)	Grade 2–4 (n = 33)
-Dilatation of the lateral cerebral ventricles, usually defined as greater than 10 mm at the level of the atria.
-Prevalence of 0.3–1.5 per 1000 live births.
WMI (Perlman et al. 1996; Volpe 1997; Imamura et al. 2013)	Grade 0–1 (n = 196)	Grade 2–3 (n = 57)
-Type of brain damage that affects the brain’s white matter and can lead to a series of disabilities, including cerebral palsy.
-Reported incidence of PVL varies from 3% to 15%.
-Periventricular leukomalacia is seen in 3% to 10% of premature neonates.