Abstract

The objectives were to study ultrasound (US), magnetic resonance imaging (MRI), single photon emission tomography (SPET) and brainstem auditory evoked potentials (BAEP) as structural and functional imaging methods for the prediction of later neuromotor outcome and to assess the reliability of auditory brainstem responses (ABR), transient evoked otoacoustic emissions (TEOAE) and free-field auditory behavioural responses (FF) for the prediction of permanent hearing loss.

The series comprised 51 surviving very low birth weight preterm infants born at < 34 gestational weeks with a birth weight < 1500 grams, taking 52 full-term infants as controls with respect to hearing screening and 21 with respect to brainstem function. The imaging examinations and hearing screening were performed at term age and follow-up continued to a corrected age of 18 months for the evaluation of neurodevelopment and hearing. MRI images were analysed with regard to the degree of myelination, parenchymal lesions, ventricular-brain ratios and widths of the extracerebral spaces, and the predictive value of the findings for later neuromotor development was assessed by comparison with US. In the SPET examinations (on 34 infants) relative regional perfusion levels and hemispheric asymmetries were evaluated in slices. The predictive value of perfusion defects in SPET was similarly assessed relative to US abnormalities. Brainstem size was measured by MRI, and brainstem function evaluated by BAEP, and results being used to predict neurosensory disability. Hearing was screened by means of TEOAE, ABR and FF, and the results used to predict permanent hearing loss. Parenchymal lesions in MRI predicted cerebral palsy (CP) with a sensitivity of 82% and a specificity of 97%, the corresponding figures for US being 58% and 100%. Delayed myelination, ventricular-brain ratios and widths of the extracerebral spaces failed to predict CP. The sensitivity of perfusion defects in SPET for predicting CP was 82% and the specificity 70%, and correspondingly US attained a sensitivity of 73% and a specificity of 83%. The best brainstem dimensions for predicting neurosensory disability reached at sensitivity of 23–31% and a specificity of 97–100%. The best predictors in BAEP gave the sensitivity of 93% with a specificity of 57–59%. Bilateral failure in TEOAE predicted hearing loss with a sensitivity of 50% and with a specificity of 84%, and that in ABR with a sensitivity of 100% and a specificity of 98%. The FF examination showed a sensitivity of 50% and a specificity of 98%.

In conclusion, out of the brain imaging methods used here MRI was the best for predicting abnormal neuromotor outcome. Brainstem dimensions in MRI appear to predict neurosensory disability poorly, however, whereas BAEP shows a better prediction value, but is limited by a low specificity. ABR seems to be the best hearing screening method because it includes retrocochlear involvements in preterm infants.