6.6. Clinical implications

As long as our efforts to prevent preterm births continue to be unsuccessful, there will be high-risk preterm infants. To be born too prematurely, and to have been exposed to inadequately distributed brain perfusion during perinatal and neonatal life are major risks with regard to CP. We do not know what an infant has suffered, however, or how much this will contribute to the development of a later disability. Although the plasticity of the developing nervous system is enormous an uneventful neonatal period cannot guarantee normality. A structural neonatal clinical neurological examination requires experienced staff, takes a considerable time and frequently has to be repeated, and in any case the result depends very much on the condition and age of the infant. Its sensitivity in predicting the outcome will still be uncertain, and a follow-up will be needed. Concern over the proportion of preterm survivors with disabilities has led us to study the possibilities for identifying as early as possible the structural and functional lesions which cause major difficulties for preterm infants at a later stage and to focus resources on these.

Any lesion in a living preterm infant that involves the brain parenchyma, including haemorrhagic lesions, porencephalic cysts and cystic leukomalacia, or intraventiricular haemorrhage complicated by ventricular dilatation, must be defined as a major cerebral abnormality and can frequently be expected to lead to neuromotor and sensory disabilities. Lesions in the brainstem and the auditory pathways of surviving preterm infants are less often assessed.

Although US, MRI and SPET are based on different phenomena and may predict different entities, these methods were used in an attempt to identify changes in the brain that might be predictive of the neuromotor outcome. MRI at term age was more sensitive to parenchymal changes than US. Although the main prediction end point for the US, MRI and SPET examinations may be the motor outcome, not only white matter damage should be highlighted. As lesions of the grey matter in cortical areas and the thalamus are often reflections of white matter loss or infarcts, it seems that perfusion defects in SPET can achieve a moderate predictive value with regard to motor disability. Similarly, germinal matrix area abnormalities may be connected with more diffuse, invisible white matter injury, and the deep grey matter areas (the thalamus and basal ganglia) may be damaged with functional impairments or disabilities later in childhood, adolescence and adulthood.

Brainstem lesions in MRI of surviving preterm infants remained of low-significance although the mean diameters of the brainstem were smaller in the infants with neurosensory disability than in those with a normal outcome. Thus brainstem MRI cannot be used as the sole predictor of disabilities. BAEP, being a functional measure, achieved a much better predictive value.

Out of the tests used for auditory screening in this series, TEOAE was disturbed far too often when applied to preterm infants and FF identified only a half of the disabled cases, thus attaining poorer predictive values than ABR. This latter identified all the preterm infants with permanent hearing loss, possibly due to its ability to detect retrocochlear damage, which may affect preterm infants more often than full-term ones. ABR should therefore be recommended for the term age screening of hearing in preterm infants.